[llvm-commits] [llvm] r71588 - in /llvm/trunk/lib/CodeGen: PEI.h PrologEpilogInserter.cpp ShrinkWrapping.cpp
John Mosby
ojomojo at gmail.com
Tue May 12 13:33:29 PDT 2009
Author: jdm
Date: Tue May 12 15:33:29 2009
New Revision: 71588
URL: http://llvm.org/viewvc/llvm-project?rev=71588&view=rev
Log:
Restructure PEI code:
- moved shrink wrapping code from PrologEpilogInserter.cpp to
new file ShrinkWrapping.cpp.
- moved PEI pass definition into new shared header PEI.h.
Added:
llvm/trunk/lib/CodeGen/PEI.h
llvm/trunk/lib/CodeGen/ShrinkWrapping.cpp
Modified:
llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp
Added: llvm/trunk/lib/CodeGen/PEI.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PEI.h?rev=71588&view=auto
==============================================================================
--- llvm/trunk/lib/CodeGen/PEI.h (added)
+++ llvm/trunk/lib/CodeGen/PEI.h Tue May 12 15:33:29 2009
@@ -0,0 +1,167 @@
+//===-- PrologEpilogInserter.h - Prolog/Epilog code insertion -*- C++ -* --===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass is responsible for finalizing the functions frame layout, saving
+// callee saved registers, and for emitting prolog & epilog code for the
+// function.
+//
+// This pass must be run after register allocation. After this pass is
+// executed, it is illegal to construct MO_FrameIndex operands.
+//
+// This pass also implements a shrink wrapping variant of prolog/epilog
+// insertion.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_PEI_H
+#define LLVM_CODEGEN_PEI_H
+
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/ADT/DenseMap.h"
+
+namespace llvm {
+ class RegScavenger;
+ class MachineBasicBlock;
+
+ class PEI : public MachineFunctionPass {
+ public:
+ static char ID;
+ PEI() : MachineFunctionPass(&ID) {}
+
+ const char *getPassName() const {
+ return "Prolog/Epilog Insertion & Frame Finalization";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+ /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
+ /// frame indexes with appropriate references.
+ ///
+ bool runOnMachineFunction(MachineFunction &Fn);
+
+ private:
+ RegScavenger *RS;
+
+ // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
+ // stack frame indexes.
+ unsigned MinCSFrameIndex, MaxCSFrameIndex;
+
+ // Analysis info for spill/restore placement.
+ // "CSR": "callee saved register".
+
+ // CSRegSet contains indices into the Callee Saved Register Info
+ // vector built by calculateCalleeSavedRegisters() and accessed
+ // via MF.getFrameInfo()->getCalleeSavedInfo().
+ typedef SparseBitVector<> CSRegSet;
+
+ // CSRegBlockMap maps MachineBasicBlocks to sets of callee
+ // saved register indices.
+ typedef DenseMap<MachineBasicBlock*, CSRegSet> CSRegBlockMap;
+
+ // Set and maps for computing CSR spill/restore placement:
+ // used in function (UsedCSRegs)
+ // used in a basic block (CSRUsed)
+ // anticipatable in a basic block (Antic{In,Out})
+ // available in a basic block (Avail{In,Out})
+ // to be spilled at the entry to a basic block (CSRSave)
+ // to be restored at the end of a basic block (CSRRestore)
+ CSRegSet UsedCSRegs;
+ CSRegBlockMap CSRUsed;
+ CSRegBlockMap AnticIn, AnticOut;
+ CSRegBlockMap AvailIn, AvailOut;
+ CSRegBlockMap CSRSave;
+ CSRegBlockMap CSRRestore;
+
+ // Entry and return blocks of the current function.
+ MachineBasicBlock* EntryBlock;
+ SmallVector<MachineBasicBlock*, 4> ReturnBlocks;
+
+ // Map of MBBs to top level MachineLoops.
+ DenseMap<MachineBasicBlock*, MachineLoop*> TLLoops;
+
+ // Flag to control shrink wrapping per-function:
+ // may choose to skip shrink wrapping for certain
+ // functions.
+ bool ShrinkWrapThisFunction;
+
+#ifndef NDEBUG
+ // Machine function handle.
+ MachineFunction* MF;
+
+ // Flag indicating that the current function
+ // has at least one "short" path in the machine
+ // CFG from the entry block to an exit block.
+ bool HasFastExitPath;
+#endif
+
+ bool calculateSets(MachineFunction &Fn);
+ bool calcAnticInOut(MachineBasicBlock* MBB);
+ bool calcAvailInOut(MachineBasicBlock* MBB);
+ void calculateAnticAvail(MachineFunction &Fn);
+ bool addUsesForMEMERegion(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4>& blks);
+ bool addUsesForTopLevelLoops(SmallVector<MachineBasicBlock*, 4>& blks);
+ bool calcSpillPlacements(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4> &blks,
+ CSRegBlockMap &prevSpills);
+ bool calcRestorePlacements(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4> &blks,
+ CSRegBlockMap &prevRestores);
+ void placeSpillsAndRestores(MachineFunction &Fn);
+ void placeCSRSpillsAndRestores(MachineFunction &Fn);
+ void calculateCalleeSavedRegisters(MachineFunction &Fn);
+ void insertCSRSpillsAndRestores(MachineFunction &Fn);
+ void calculateFrameObjectOffsets(MachineFunction &Fn);
+ void replaceFrameIndices(MachineFunction &Fn);
+ void insertPrologEpilogCode(MachineFunction &Fn);
+
+ // Initialize DFA sets, called before iterations.
+ void clearAnticAvailSets();
+ // Clear all sets constructed by shrink wrapping.
+ void clearAllSets();
+
+ // Initialize all shrink wrapping data.
+ void initShrinkWrappingInfo();
+
+ // Convienences for dealing with machine loops.
+ MachineBasicBlock* getTopLevelLoopPreheader(MachineLoop* LP);
+ MachineLoop* getTopLevelLoopParent(MachineLoop *LP);
+
+ // Propgate CSRs used in MBB to all MBBs of loop LP.
+ void propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP);
+
+ // Convenience for recognizing return blocks.
+ bool isReturnBlock(MachineBasicBlock* MBB);
+
+#ifndef NDEBUG
+ // Debugging methods.
+
+ // Mark this function as having fast exit paths.
+ void findFastExitPath();
+
+ // Verify placement of spills/restores.
+ void verifySpillRestorePlacement();
+
+ std::string getBasicBlockName(const MachineBasicBlock* MBB);
+ std::string stringifyCSRegSet(const CSRegSet& s);
+ void dumpSet(const CSRegSet& s);
+ void dumpUsed(MachineBasicBlock* MBB);
+ void dumpAllUsed();
+ void dumpSets(MachineBasicBlock* MBB);
+ void dumpSets1(MachineBasicBlock* MBB);
+ void dumpAllSets();
+ void dumpSRSets();
+#endif
+
+ };
+} // End llvm namespace
+#endif
Modified: llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp?rev=71588&r1=71587&r2=71588&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp (original)
+++ llvm/trunk/lib/CodeGen/PrologEpilogInserter.cpp Tue May 12 15:33:29 2009
@@ -14,35 +14,14 @@
// This pass must be run after register allocation. After this pass is
// executed, it is illegal to construct MO_FrameIndex operands.
//
-// This pass implements a shrink wrapping variant of prolog/epilog insertion:
-// - Places callee saved register (CSR) spills and restores in the CFG to
-// tightly surround uses so that execution paths that do not use CSRs do not
-// pay the spill/restore penalty.
-//
-// - Avoiding placment of spills/restores in loops: if a CSR is used inside a
-// loop(nest), the spills are placed in the loop preheader, and restores are
-// placed in the loop exit nodes (the successors of the loop _exiting_ nodes).
-//
-// - Covering paths without CSR uses: e.g. if a restore is placed in a join
-// block, a matching spill is added to the end of all immediate predecessor
-// blocks that are not reached by a spill. Similarly for saves placed in
-// branch blocks.
-//
-// Shrink wrapping uses an analysis similar to the one in GVNPRE to determine
-// which basic blocks require callee-saved register save/restore code.
-//
-// This pass uses MachineDominators and MachineLoopInfo. Loop information
-// is used to prevent shrink wrapping of callee-saved register save/restore
-// code into loops.
+// This pass provides an optional shrink wrapping variant of prolog/epilog
+// insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "shrink-wrap"
-
-#include "llvm/CodeGen/Passes.h"
+#include "PEI.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
@@ -52,1009 +31,91 @@
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/ADT/SparseBitVector.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/PostOrderIterator.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
-#include "llvm/Support/Debug.h"
#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/Statistic.h"
#include <climits>
-#include <sstream>
using namespace llvm;
-STATISTIC(numSRReduced, "Number of CSR spills+restores reduced.");
-
-// Shrink Wrapping:
-static cl::opt<bool>
-ShrinkWrapping("shrink-wrap",
- cl::desc("Shrink wrap callee-saved register spills/restores"));
-
-// Shrink wrap only the specified function, a debugging aid.
-static cl::opt<std::string>
-ShrinkWrapFunc("shrink-wrap-func", cl::Hidden,
- cl::desc("Shrink wrap the specified function"),
- cl::value_desc("funcname"),
- cl::init(""));
-
-// Debugging level for shrink wrapping.
-enum ShrinkWrapDebugLevel {
- None, BasicInfo, Iterations, Details
-};
-
-static cl::opt<enum ShrinkWrapDebugLevel>
-ShrinkWrapDebugging("shrink-wrap-dbg", cl::Hidden,
- cl::desc("Print shrink wrapping debugging information"),
- cl::values(
- clEnumVal(None , "disable debug output"),
- clEnumVal(BasicInfo , "print basic DF sets"),
- clEnumVal(Iterations, "print SR sets for each iteration"),
- clEnumVal(Details , "print all DF sets"),
- clEnumValEnd));
-
-
-namespace {
- struct VISIBILITY_HIDDEN PEI : public MachineFunctionPass {
- static char ID;
- PEI() : MachineFunctionPass(&ID) {}
-
- const char *getPassName() const {
- return "Prolog/Epilog Insertion & Frame Finalization";
- }
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
- if (ShrinkWrapping || ShrinkWrapFunc != "") {
- AU.addRequired<MachineLoopInfo>();
- AU.addRequired<MachineDominatorTree>();
- }
- AU.addPreserved<MachineLoopInfo>();
- AU.addPreserved<MachineDominatorTree>();
- MachineFunctionPass::getAnalysisUsage(AU);
- }
-
- /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
- /// frame indexes with appropriate references.
- ///
- bool runOnMachineFunction(MachineFunction &Fn) {
- const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
- RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
-
- DEBUG(MF = &Fn);
-
- // Get MachineModuleInfo so that we can track the construction of the
- // frame.
- if (MachineModuleInfo *MMI = getAnalysisIfAvailable<MachineModuleInfo>())
- Fn.getFrameInfo()->setMachineModuleInfo(MMI);
-
- // Allow the target machine to make some adjustments to the function
- // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
- TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
-
- // Scan the function for modified callee saved registers and insert spill
- // code for any callee saved registers that are modified. Also calculate
- // the MaxCallFrameSize and HasCalls variables for the function's frame
- // information and eliminates call frame pseudo instructions.
- calculateCalleeSavedRegisters(Fn);
-
- // Determine placement of CSR spill/restore code:
- // - with shrink wrapping, place spills and restores to tightly
- // enclose regions in the Machine CFG of the function where
- // they are used. Without shrink wrapping
- // - default (no shrink wrapping), place all spills in the
- // entry block, all restores in return blocks.
- placeCSRSpillsAndRestores(Fn);
-
- // Add the code to save and restore the callee saved registers
- insertCSRSpillsAndRestores(Fn);
-
- // Allow the target machine to make final modifications to the function
- // before the frame layout is finalized.
- TRI->processFunctionBeforeFrameFinalized(Fn);
-
- // Calculate actual frame offsets for all abstract stack objects...
- calculateFrameObjectOffsets(Fn);
-
- // Add prolog and epilog code to the function. This function is required
- // to align the stack frame as necessary for any stack variables or
- // called functions. Because of this, calculateCalleeSavedRegisters
- // must be called before this function in order to set the HasCalls
- // and MaxCallFrameSize variables.
- insertPrologEpilogCode(Fn);
-
- // Replace all MO_FrameIndex operands with physical register references
- // and actual offsets.
- //
- replaceFrameIndices(Fn);
-
- delete RS;
- clearAllSets();
- return true;
- }
-
- private:
- RegScavenger *RS;
-
- // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
- // stack frame indexes.
- unsigned MinCSFrameIndex, MaxCSFrameIndex;
-
- // Analysis info for spill/restore placement.
- // "CSR": "callee saved register".
-
- // CSRegSet contains indices into the Callee Saved Register Info
- // vector built by calculateCalleeSavedRegisters() and accessed
- // via MF.getFrameInfo()->getCalleeSavedInfo().
- typedef SparseBitVector<> CSRegSet;
-
- // CSRegBlockMap maps MachineBasicBlocks to sets of callee
- // saved register indices.
- typedef DenseMap<MachineBasicBlock*, CSRegSet> CSRegBlockMap;
-
- // Set and maps for computing CSR spill/restore placement:
- // used in function (UsedCSRegs)
- // used in a basic block (CSRUsed)
- // anticipatable in a basic block (Antic{In,Out})
- // available in a basic block (Avail{In,Out})
- // to be spilled at the entry to a basic block (CSRSave)
- // to be restored at the end of a basic block (CSRRestore)
- CSRegSet UsedCSRegs;
- CSRegBlockMap CSRUsed;
- CSRegBlockMap AnticIn, AnticOut;
- CSRegBlockMap AvailIn, AvailOut;
- CSRegBlockMap CSRSave;
- CSRegBlockMap CSRRestore;
-
- // Entry and return blocks of the current function.
- MachineBasicBlock* EntryBlock;
- SmallVector<MachineBasicBlock*, 4> ReturnBlocks;
-
- // Map of MBBs to top level MachineLoops.
- DenseMap<MachineBasicBlock*, MachineLoop*> TLLoops;
-
- // Flag to control shrink wrapping per-function:
- // may choose to skip shrink wrapping for certain
- // functions.
- bool ShrinkWrapThisFunction;
-
-#ifndef NDEBUG
- // Machine function handle.
- MachineFunction* MF;
-
- // Flag indicating that the current function
- // has at least one "short" path in the machine
- // CFG from the entry block to an exit block.
- bool HasFastExitPath;
-#endif
-
- bool calculateSets(MachineFunction &Fn);
- bool calcAnticInOut(MachineBasicBlock* MBB);
- bool calcAvailInOut(MachineBasicBlock* MBB);
- void calculateAnticAvail(MachineFunction &Fn);
- bool addUsesForMEMERegion(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4>& blks);
- bool addUsesForTopLevelLoops(SmallVector<MachineBasicBlock*, 4>& blks);
- bool calcSpillPlacements(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4> &blks,
- CSRegBlockMap &prevSpills);
- bool calcRestorePlacements(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4> &blks,
- CSRegBlockMap &prevRestores);
- void placeSpillsAndRestores(MachineFunction &Fn);
- void placeCSRSpillsAndRestores(MachineFunction &Fn);
- void calculateCalleeSavedRegisters(MachineFunction &Fn);
- void insertCSRSpillsAndRestores(MachineFunction &Fn);
- void calculateFrameObjectOffsets(MachineFunction &Fn);
- void replaceFrameIndices(MachineFunction &Fn);
- void insertPrologEpilogCode(MachineFunction &Fn);
-
- // Initialize DFA sets, called before iterations.
- void clearAnticAvailSets();
- // Clear all sets constructed by shrink wrapping.
- void clearAllSets();
-
- // Initialize all shrink wrapping data.
- void initShrinkWrappingInfo();
-
- // Convienences for dealing with machine loops.
- MachineBasicBlock* getTopLevelLoopPreheader(MachineLoop* LP) {
- assert(LP && "Machine loop is NULL.");
- MachineBasicBlock* PHDR = LP->getLoopPreheader();
- MachineLoop* PLP = LP->getParentLoop();
- while (PLP) {
- PHDR = PLP->getLoopPreheader();
- PLP = PLP->getParentLoop();
- }
- return PHDR;
- }
-
- MachineLoop* getTopLevelLoopParent(MachineLoop *LP) {
- if (LP == 0)
- return 0;
- MachineLoop* PLP = LP->getParentLoop();
- while (PLP) {
- LP = PLP;
- PLP = PLP->getParentLoop();
- }
- return LP;
- }
-
- // Propgate CSRs used in MBB to all MBBs of loop LP.
- void propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP);
-
- // Convenience for recognizing return blocks.
- bool isReturnBlock(MachineBasicBlock* MBB) {
- return (MBB && !MBB->empty() && MBB->back().getDesc().isReturn());
- }
-
-#ifndef NDEBUG
- // Debugging methods.
-
- // Mark this function as having fast exit paths.
- void findFastExitPath();
-
- // Verify placement of spills/restores.
- void verifySpillRestorePlacement();
-
- std::string getBasicBlockName(const MachineBasicBlock* MBB);
- std::string stringifyCSRegSet(const CSRegSet& s);
- void dumpSet(const CSRegSet& s);
- void dumpUsed(MachineBasicBlock* MBB);
- void dumpAllUsed();
- void dumpSets(MachineBasicBlock* MBB);
- void dumpSets1(MachineBasicBlock* MBB);
- void dumpAllSets();
- void dumpSRSets();
-#endif
-
- };
- char PEI::ID = 0;
-}
-
-// Initialize shrink wrapping DFA sets, called before iterations.
-void PEI::clearAnticAvailSets() {
- AnticIn.clear();
- AnticOut.clear();
- AvailIn.clear();
- AvailOut.clear();
-}
-
-// Clear all sets constructed by shrink wrapping.
-void PEI::clearAllSets() {
- ReturnBlocks.clear();
- clearAnticAvailSets();
- UsedCSRegs.clear();
- CSRUsed.clear();
- TLLoops.clear();
- CSRSave.clear();
- CSRRestore.clear();
-}
-
-// Initialize all shrink wrapping data.
-void PEI::initShrinkWrappingInfo() {
- clearAllSets();
- EntryBlock = 0;
-#ifndef NDEBUG
- HasFastExitPath = false;
-#endif
- ShrinkWrapThisFunction = ShrinkWrapping;
- // DEBUG: enable or disable shrink wrapping for the current function
- // via --shrink-wrap-func=<funcname>.
-#ifndef NDEBUG
- if (ShrinkWrapFunc != "") {
- std::string MFName = MF->getFunction()->getName();
- ShrinkWrapThisFunction = (MFName == ShrinkWrapFunc);
- }
-#endif
-}
+char PEI::ID = 0;
+static RegisterPass<PEI>
+X("prologepilog", "Prologue/Epilogue Insertion");
/// createPrologEpilogCodeInserter - This function returns a pass that inserts
/// prolog and epilog code, and eliminates abstract frame references.
///
FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
-/// placeCSRSpillsAndRestores - determine which MBBs of the function
-/// need save, restore code for callee-saved registers by doing a DF analysis
-/// similar to the one used in code motion (GVNPRE). This produces maps of MBBs
-/// to sets of registers (CSRs) for saves and restores. MachineLoopInfo
-/// is used to ensure that CSR save/restore code is not placed inside loops.
-/// This function computes the maps of MBBs -> CSRs to spill and restore
-/// in CSRSave, CSRRestore.
-///
-/// If shrink wrapping is not being performed, place all spills in
-/// the entry block, all restores in return blocks. In this case,
-/// CSRSave has a single mapping, CSRRestore has mappings for each
-/// return block.
-///
-void PEI::placeCSRSpillsAndRestores(MachineFunction &Fn) {
-
- initShrinkWrappingInfo();
-
- DEBUG(if (ShrinkWrapThisFunction) {
- DOUT << "Place CSR spills/restores for "
- << MF->getFunction()->getName() << "\n";
- });
-
- if (calculateSets(Fn))
- placeSpillsAndRestores(Fn);
-}
-
-/// calcAnticInOut - calculate the anticipated in/out reg sets
-/// for the given MBB by looking forward in the MCFG at MBB's
-/// successors.
-///
-bool PEI::calcAnticInOut(MachineBasicBlock* MBB) {
- bool changed = false;
-
- // AnticOut[MBB] = INTERSECT(AnticIn[S] for S in SUCCESSORS(MBB))
- SmallVector<MachineBasicBlock*, 4> successors;
- for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
- SE = MBB->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
- if (SUCC != MBB)
- successors.push_back(SUCC);
- }
-
- unsigned i = 0, e = successors.size();
- if (i != e) {
- CSRegSet prevAnticOut = AnticOut[MBB];
- MachineBasicBlock* SUCC = successors[i];
-
- AnticOut[MBB] = AnticIn[SUCC];
- for (++i; i != e; ++i) {
- SUCC = successors[i];
- AnticOut[MBB] &= AnticIn[SUCC];
- }
- if (prevAnticOut != AnticOut[MBB])
- changed = true;
- }
-
- // AnticIn[MBB] = UNION(CSRUsed[MBB], AnticOut[MBB]);
- CSRegSet prevAnticIn = AnticIn[MBB];
- AnticIn[MBB] = CSRUsed[MBB] | AnticOut[MBB];
- if (prevAnticIn |= AnticIn[MBB])
- changed = true;
- return changed;
-}
-
-/// calcAvailInOut - calculate the available in/out reg sets
-/// for the given MBB by looking backward in the MCFG at MBB's
-/// predecessors.
-///
-bool PEI::calcAvailInOut(MachineBasicBlock* MBB) {
- bool changed = false;
-
- // AvailIn[MBB] = INTERSECT(AvailOut[P] for P in PREDECESSORS(MBB))
- SmallVector<MachineBasicBlock*, 4> predecessors;
- for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
- PE = MBB->pred_end(); PI != PE; ++PI) {
- MachineBasicBlock* PRED = *PI;
- if (PRED != MBB)
- predecessors.push_back(PRED);
- }
-
- unsigned i = 0, e = predecessors.size();
- if (i != e) {
- CSRegSet prevAvailIn = AvailIn[MBB];
- MachineBasicBlock* PRED = predecessors[i];
-
- AvailIn[MBB] = AvailOut[PRED];
- for (++i; i != e; ++i) {
- PRED = predecessors[i];
- AvailIn[MBB] &= AvailOut[PRED];
- }
- if (prevAvailIn != AvailIn[MBB])
- changed = true;
- }
-
- // AvailOut[MBB] = UNION(CSRUsed[MBB], AvailIn[MBB]);
- CSRegSet prevAvailOut = AvailOut[MBB];
- AvailOut[MBB] = CSRUsed[MBB] | AvailIn[MBB];
- if (prevAvailOut |= AvailOut[MBB])
- changed = true;
- return changed;
-}
-
-/// calculateAnticAvail - build the sets anticipated and available
-/// registers in the MCFG of the current function iteratively,
-/// doing a combined forward and backward analysis.
+/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
+/// frame indexes with appropriate references.
///
-void PEI::calculateAnticAvail(MachineFunction &Fn) {
- // Initialize data flow sets.
- clearAnticAvailSets();
-
- // Calulate Antic{In,Out} and Avail{In,Out} iteratively on the MCFG.
- bool changed = true;
- unsigned iterations = 0;
- while (changed) {
- changed = false;
- ++iterations;
- for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
-
- // Calculate anticipated in, out regs at MBB from
- // anticipated at successors of MBB.
- changed |= calcAnticInOut(MBB);
-
- // Calculate available in, out regs at MBB from
- // available at predecessors of MBB.
- changed |= calcAvailInOut(MBB);
- }
- }
-
- DEBUG(if (ShrinkWrapDebugging >= Details) {
- DOUT << "-----------------------------------------------------------\n";
- DOUT << " Antic/Avail Sets:\n";
- DOUT << "-----------------------------------------------------------\n";
- DOUT << "iterations = " << iterations << "\n";
- DOUT << "-----------------------------------------------------------\n";
- DOUT << "MBB | USED | ANTIC_IN | ANTIC_OUT | AVAIL_IN | AVAIL_OUT\n";
- DOUT << "-----------------------------------------------------------\n";
- for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- dumpSets(MBB);
- }
- DOUT << "-----------------------------------------------------------\n";
- });
-}
-
-/// propagateUsesAroundLoop - copy used register info from MBB to all blocks
-/// of the loop given by LP and its parent loops. This prevents spills/restores
-/// from being placed in the bodies of loops.
-///
-void PEI::propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP) {
- if (! MBB || !LP)
- return;
-
- std::vector<MachineBasicBlock*> loopBlocks = LP->getBlocks();
- for (unsigned i = 0, e = loopBlocks.size(); i != e; ++i) {
- MachineBasicBlock* LBB = loopBlocks[i];
- if (LBB == MBB)
- continue;
- if (CSRUsed[LBB].contains(CSRUsed[MBB]))
- continue;
- CSRUsed[LBB] |= CSRUsed[MBB];
- }
-}
-
-/// calculateSets - collect the CSRs used in this function, compute
-/// the DF sets that describe the initial minimal regions in the
-/// Machine CFG around which CSR spills and restores must be placed.
-///
-/// Additionally, this function decides if shrink wrapping should
-/// be disabled for the current function, checking the following:
-/// 1. the current function has more than 500 MBBs: heuristic limit
-/// on function size to reduce compile time impact of the current
-/// iterative algorithm.
-/// 2. all CSRs are used in the entry block.
-/// 3. all CSRs are used in all immediate successors of the entry block.
-/// 4. all CSRs are used in a subset of blocks, each of which dominates
-/// all return blocks. These blocks, taken as a subgraph of the MCFG,
-/// are equivalent to the entry block since all execution paths pass
-/// through them.
-///
-bool PEI::calculateSets(MachineFunction &Fn) {
- // Sets used to compute spill, restore placement sets.
- const std::vector<CalleeSavedInfo> CSI =
- Fn.getFrameInfo()->getCalleeSavedInfo();
-
- // If no CSRs used, we are done.
- if (CSI.empty()) {
- DEBUG(if (ShrinkWrapThisFunction)
- DOUT << "DISABLED: " << Fn.getFunction()->getName()
- << ": uses no callee-saved registers\n");
- return false;
- }
-
- // Save refs to entry and return blocks.
- EntryBlock = Fn.begin();
- for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end();
- MBB != E; ++MBB)
- if (isReturnBlock(MBB))
- ReturnBlocks.push_back(MBB);
-
- // Determine if this function has fast exit paths.
- DEBUG(if (ShrinkWrapThisFunction)
- findFastExitPath());
-
- // Limit shrink wrapping via the current iterative bit vector
- // implementation to functions with <= 500 MBBs.
- if (Fn.size() > 500) {
- DEBUG(if (ShrinkWrapThisFunction)
- DOUT << "DISABLED: " << Fn.getFunction()->getName()
- << ": too large (" << Fn.size() << " MBBs)\n");
- ShrinkWrapThisFunction = false;
- }
-
- // Return now if not shrink wrapping.
- if (! ShrinkWrapThisFunction)
- return false;
-
- // Collect set of used CSRs.
- for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
- UsedCSRegs.set(inx);
- }
-
- // Walk instructions in all MBBs, create CSRUsed[] sets, choose
- // whether or not to shrink wrap this function.
- MachineLoopInfo &LI = getAnalysis<MachineLoopInfo>();
- MachineDominatorTree &DT = getAnalysis<MachineDominatorTree>();
+bool PEI::runOnMachineFunction(MachineFunction &Fn) {
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
+ RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
- bool allCSRUsesInEntryBlock = true;
- for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- for (MachineBasicBlock::iterator I = MBB->begin(); I != MBB->end(); ++I) {
- for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
- unsigned Reg = CSI[inx].getReg();
- // If instruction I reads or modifies Reg, add it to UsedCSRegs,
- // CSRUsed map for the current block.
- for (unsigned opInx = 0, opEnd = I->getNumOperands();
- opInx != opEnd; ++opInx) {
- const MachineOperand &MO = I->getOperand(opInx);
- if (! (MO.isReg() && (MO.isUse() || MO.isDef())))
- continue;
- unsigned MOReg = MO.getReg();
- if (!MOReg)
- continue;
- if (MOReg == Reg ||
- (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
- TargetRegisterInfo::isPhysicalRegister(Reg) &&
- TRI->isSubRegister(Reg, MOReg))) {
- // CSR Reg is defined/used in block MBB.
- CSRUsed[MBB].set(inx);
- // Check for uses in EntryBlock.
- if (MBB != EntryBlock)
- allCSRUsesInEntryBlock = false;
- }
- }
- }
- }
-
- if (CSRUsed[MBB].empty())
- continue;
-
- // Propagate CSRUsed[MBB] in loops
- if (MachineLoop* LP = LI.getLoopFor(MBB)) {
- // Add top level loop to work list.
- MachineBasicBlock* HDR = getTopLevelLoopPreheader(LP);
- MachineLoop* PLP = getTopLevelLoopParent(LP);
-
- if (! HDR) {
- HDR = PLP->getHeader();
- assert(HDR->pred_size() > 0 && "Loop header has no predecessors?");
- MachineBasicBlock::pred_iterator PI = HDR->pred_begin();
- HDR = *PI;
- }
- TLLoops[HDR] = PLP;
-
- // Push uses from inside loop to its parent loops,
- // or to all other MBBs in its loop.
- if (LP->getLoopDepth() > 1) {
- for (MachineLoop* PLP = LP->getParentLoop(); PLP;
- PLP = PLP->getParentLoop()) {
- propagateUsesAroundLoop(MBB, PLP);
- }
- } else {
- propagateUsesAroundLoop(MBB, LP);
- }
- }
- }
-
- if (allCSRUsesInEntryBlock) {
- DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
- << ": all CSRs used in EntryBlock\n");
- ShrinkWrapThisFunction = false;
- } else {
- bool allCSRsUsedInEntryFanout = true;
- for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(),
- SE = EntryBlock->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
- if (CSRUsed[SUCC] != UsedCSRegs)
- allCSRsUsedInEntryFanout = false;
- }
- if (allCSRsUsedInEntryFanout) {
- DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
- << ": all CSRs used in imm successors of EntryBlock\n");
- ShrinkWrapThisFunction = false;
- }
- }
-
- if (ShrinkWrapThisFunction) {
- // Check if MBB uses CSRs and dominates all exit nodes.
- // Such nodes are equiv. to the entry node w.r.t.
- // CSR uses: every path through the function must
- // pass through this node. If each CSR is used at least
- // once by these nodes, shrink wrapping is disabled.
- CSRegSet CSRUsedInChokePoints;
- for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- if (MBB == EntryBlock || CSRUsed[MBB].empty() || MBB->succ_size() < 1)
- continue;
- bool dominatesExitNodes = true;
- for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
- if (! DT.dominates(MBB, ReturnBlocks[ri])) {
- dominatesExitNodes = false;
- break;
- }
- if (dominatesExitNodes) {
- CSRUsedInChokePoints |= CSRUsed[MBB];
- if (CSRUsedInChokePoints == UsedCSRegs) {
- DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
- << ": all CSRs used in choke point(s) at "
- << getBasicBlockName(MBB) << "\n");
- ShrinkWrapThisFunction = false;
- break;
- }
- }
- }
- }
+ // Get MachineModuleInfo so that we can track the construction of the
+ // frame.
+ if (MachineModuleInfo *MMI = getAnalysisIfAvailable<MachineModuleInfo>())
+ Fn.getFrameInfo()->setMachineModuleInfo(MMI);
+
+ // Allow the target machine to make some adjustments to the function
+ // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
+ TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
+
+ // Scan the function for modified callee saved registers and insert spill
+ // code for any callee saved registers that are modified. Also calculate
+ // the MaxCallFrameSize and HasCalls variables for the function's frame
+ // information and eliminates call frame pseudo instructions.
+ calculateCalleeSavedRegisters(Fn);
+
+ // Determine placement of CSR spill/restore code:
+ // - with shrink wrapping, place spills and restores to tightly
+ // enclose regions in the Machine CFG of the function where
+ // they are used. Without shrink wrapping
+ // - default (no shrink wrapping), place all spills in the
+ // entry block, all restores in return blocks.
+ placeCSRSpillsAndRestores(Fn);
+
+ // Add the code to save and restore the callee saved registers
+ insertCSRSpillsAndRestores(Fn);
+
+ // Allow the target machine to make final modifications to the function
+ // before the frame layout is finalized.
+ TRI->processFunctionBeforeFrameFinalized(Fn);
+
+ // Calculate actual frame offsets for all abstract stack objects...
+ calculateFrameObjectOffsets(Fn);
+
+ // Add prolog and epilog code to the function. This function is required
+ // to align the stack frame as necessary for any stack variables or
+ // called functions. Because of this, calculateCalleeSavedRegisters
+ // must be called before this function in order to set the HasCalls
+ // and MaxCallFrameSize variables.
+ insertPrologEpilogCode(Fn);
- // Return now if we have decided not to apply shrink wrapping
- // to the current function.
- if (! ShrinkWrapThisFunction)
- return false;
-
- DEBUG({
- DOUT << "ENABLED: " << Fn.getFunction()->getName();
- if (HasFastExitPath)
- DOUT << " (fast exit path)";
- DOUT << "\n";
- if (ShrinkWrapDebugging >= BasicInfo) {
- DOUT << "------------------------------"
- << "-----------------------------\n";
- DOUT << "UsedCSRegs = " << stringifyCSRegSet(UsedCSRegs) << "\n";
- if (ShrinkWrapDebugging >= Details) {
- DOUT << "------------------------------"
- << "-----------------------------\n";
- dumpAllUsed();
- }
- }
- });
-
- // Build initial DF sets to determine minimal regions in the
- // Machine CFG around which CSRs must be spilled and restored.
- calculateAnticAvail(Fn);
+ // Replace all MO_FrameIndex operands with physical register references
+ // and actual offsets.
+ //
+ replaceFrameIndices(Fn);
+ delete RS;
+ clearAllSets();
return true;
}
-/// addUsesForMEMERegion - add uses of CSRs spilled or restored in
-/// multi-entry, multi-exit (MEME) regions so spill and restore
-/// placement will not break code that enters or leaves a
-/// shrink-wrapped region by inducing spills with no matching
-/// restores or restores with no matching spills. A MEME region
-/// is a subgraph of the MCFG with multiple entry edges, multiple
-/// exit edges, or both. This code propagates use information
-/// through the MCFG until all paths requiring spills and restores
-/// _outside_ the computed minimal placement regions have been covered.
-///
-bool PEI::addUsesForMEMERegion(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4>& blks) {
- if (MBB->succ_size() < 2 && MBB->pred_size() < 2) {
- bool processThisBlock = false;
- for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
- SE = MBB->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
- if (SUCC->pred_size() > 1) {
- processThisBlock = true;
- break;
- }
- }
- if (!CSRRestore[MBB].empty() && MBB->succ_size() > 0) {
- for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
- PE = MBB->pred_end(); PI != PE; ++PI) {
- MachineBasicBlock* PRED = *PI;
- if (PRED->succ_size() > 1) {
- processThisBlock = true;
- break;
- }
- }
- }
- if (! processThisBlock)
- return false;
- }
-
- CSRegSet prop;
- if (!CSRSave[MBB].empty())
- prop = CSRSave[MBB];
- else if (!CSRRestore[MBB].empty())
- prop = CSRRestore[MBB];
- else
- prop = CSRUsed[MBB];
- if (prop.empty())
- return false;
-
- // Propagate selected bits to successors, predecessors of MBB.
- bool addedUses = false;
- for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
- SE = MBB->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
- // Self-loop
- if (SUCC == MBB)
- continue;
- if (! CSRUsed[SUCC].contains(prop)) {
- CSRUsed[SUCC] |= prop;
- addedUses = true;
- blks.push_back(SUCC);
- DEBUG(if (ShrinkWrapDebugging >= Iterations)
- DOUT << getBasicBlockName(MBB)
- << "(" << stringifyCSRegSet(prop) << ")->"
- << "successor " << getBasicBlockName(SUCC) << "\n");
- }
- }
- for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
- PE = MBB->pred_end(); PI != PE; ++PI) {
- MachineBasicBlock* PRED = *PI;
- // Self-loop
- if (PRED == MBB)
- continue;
- if (! CSRUsed[PRED].contains(prop)) {
- CSRUsed[PRED] |= prop;
- addedUses = true;
- blks.push_back(PRED);
- DEBUG(if (ShrinkWrapDebugging >= Iterations)
- DOUT << getBasicBlockName(MBB)
- << "(" << stringifyCSRegSet(prop) << ")->"
- << "predecessor " << getBasicBlockName(PRED) << "\n");
- }
- }
- return addedUses;
-}
-
-/// addUsesForTopLevelLoops - add uses for CSRs used inside top
-/// level loops to the exit blocks of those loops.
-///
-bool PEI::addUsesForTopLevelLoops(SmallVector<MachineBasicBlock*, 4>& blks) {
- bool addedUses = false;
-
- // Place restores for top level loops where needed.
- for (DenseMap<MachineBasicBlock*, MachineLoop*>::iterator
- I = TLLoops.begin(), E = TLLoops.end(); I != E; ++I) {
- MachineBasicBlock* MBB = I->first;
- MachineLoop* LP = I->second;
- MachineBasicBlock* HDR = LP->getHeader();
- SmallVector<MachineBasicBlock*, 4> exitBlocks;
- CSRegSet loopSpills;
-
- loopSpills = CSRSave[MBB];
- if (CSRSave[MBB].empty()) {
- loopSpills = CSRUsed[HDR];
- assert(!loopSpills.empty() && "No CSRs used in loop?");
- } else if (CSRRestore[MBB].contains(CSRSave[MBB]))
- continue;
-
- LP->getExitBlocks(exitBlocks);
- assert(exitBlocks.size() > 0 && "Loop has no top level exit blocks?");
- for (unsigned i = 0, e = exitBlocks.size(); i != e; ++i) {
- MachineBasicBlock* EXB = exitBlocks[i];
- if (! CSRUsed[EXB].contains(loopSpills)) {
- CSRUsed[EXB] |= loopSpills;
- addedUses = true;
- DEBUG(if (ShrinkWrapDebugging >= Iterations)
- DOUT << "LOOP " << getBasicBlockName(MBB)
- << "(" << stringifyCSRegSet(loopSpills) << ")->"
- << getBasicBlockName(EXB) << "\n");
- if (EXB->succ_size() > 1 || EXB->pred_size() > 1)
- blks.push_back(EXB);
- }
- }
- }
- return addedUses;
-}
-
-/// calcSpillPlacements - determine which CSRs should be spilled
-/// in MBB using AnticIn sets of MBB's predecessors, keeping track
-/// of changes to spilled reg sets. Add MBB to the set of blocks
-/// that need to be processed for propagating use info to cover
-/// multi-entry/exit regions.
-///
-bool PEI::calcSpillPlacements(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4> &blks,
- CSRegBlockMap &prevSpills) {
- bool placedSpills = false;
- // Intersect (CSRegs - AnticIn[P]) for P in Predecessors(MBB)
- CSRegSet anticInPreds;
- SmallVector<MachineBasicBlock*, 4> predecessors;
- for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
- PE = MBB->pred_end(); PI != PE; ++PI) {
- MachineBasicBlock* PRED = *PI;
- if (PRED != MBB)
- predecessors.push_back(PRED);
- }
- unsigned i = 0, e = predecessors.size();
- if (i != e) {
- MachineBasicBlock* PRED = predecessors[i];
- anticInPreds = UsedCSRegs - AnticIn[PRED];
- for (++i; i != e; ++i) {
- PRED = predecessors[i];
- anticInPreds &= (UsedCSRegs - AnticIn[PRED]);
- }
- } else {
- // Handle uses in entry blocks (which have no predecessors).
- // This is necessary because the DFA formulation assumes the
- // entry and (multiple) exit nodes cannot have CSR uses, which
- // is not the case in the real world.
- anticInPreds = UsedCSRegs;
- }
- // Compute spills required at MBB:
- CSRSave[MBB] |= (AnticIn[MBB] - AvailIn[MBB]) & anticInPreds;
-
- if (! CSRSave[MBB].empty()) {
- if (MBB == EntryBlock) {
- for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
- CSRRestore[ReturnBlocks[ri]] |= CSRSave[MBB];
- } else {
- // Reset all regs spilled in MBB that are also spilled in EntryBlock.
- if (CSRSave[EntryBlock].intersects(CSRSave[MBB])) {
- CSRSave[MBB] = CSRSave[MBB] - CSRSave[EntryBlock];
- }
- }
- }
- placedSpills = (CSRSave[MBB] != prevSpills[MBB]);
- prevSpills[MBB] = CSRSave[MBB];
- // Remember this block for adding restores to successor
- // blocks for multi-entry region.
- if (placedSpills)
- blks.push_back(MBB);
-
- DEBUG(if (! CSRSave[MBB].empty() && ShrinkWrapDebugging >= Iterations)
- DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRSave[MBB]) << "\n");
-
- return placedSpills;
-}
-
-/// calcRestorePlacements - determine which CSRs should be restored
-/// in MBB using AvailOut sets of MBB's succcessors, keeping track
-/// of changes to restored reg sets. Add MBB to the set of blocks
-/// that need to be processed for propagating use info to cover
-/// multi-entry/exit regions.
-///
-bool PEI::calcRestorePlacements(MachineBasicBlock* MBB,
- SmallVector<MachineBasicBlock*, 4> &blks,
- CSRegBlockMap &prevRestores) {
- bool placedRestores = false;
- // Intersect (CSRegs - AvailOut[S]) for S in Successors(MBB)
- CSRegSet availOutSucc;
- SmallVector<MachineBasicBlock*, 4> successors;
- for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
- SE = MBB->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
- if (SUCC != MBB)
- successors.push_back(SUCC);
- }
- unsigned i = 0, e = successors.size();
- if (i != e) {
- MachineBasicBlock* SUCC = successors[i];
- availOutSucc = UsedCSRegs - AvailOut[SUCC];
- for (++i; i != e; ++i) {
- SUCC = successors[i];
- availOutSucc &= (UsedCSRegs - AvailOut[SUCC]);
- }
- } else {
- if (! CSRUsed[MBB].empty() || ! AvailOut[MBB].empty()) {
- // Handle uses in return blocks (which have no successors).
- // This is necessary because the DFA formulation assumes the
- // entry and (multiple) exit nodes cannot have CSR uses, which
- // is not the case in the real world.
- availOutSucc = UsedCSRegs;
- }
- }
- // Compute restores required at MBB:
- CSRRestore[MBB] |= (AvailOut[MBB] - AnticOut[MBB]) & availOutSucc;
-
- // Postprocess restore placements at MBB.
- // Remove the CSRs that are restored in the return blocks.
- // Lest this be confusing, note that:
- // CSRSave[EntryBlock] == CSRRestore[B] for all B in ReturnBlocks.
- if (MBB->succ_size() && ! CSRRestore[MBB].empty()) {
- if (! CSRSave[EntryBlock].empty())
- CSRRestore[MBB] = CSRRestore[MBB] - CSRSave[EntryBlock];
- }
- placedRestores = (CSRRestore[MBB] != prevRestores[MBB]);
- prevRestores[MBB] = CSRRestore[MBB];
- // Remember this block for adding saves to predecessor
- // blocks for multi-entry region.
- if (placedRestores)
- blks.push_back(MBB);
-
- DEBUG(if (! CSRRestore[MBB].empty() && ShrinkWrapDebugging >= Iterations)
- DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRRestore[MBB]) << "\n");
-
- return placedRestores;
-}
-
-/// placeSpillsAndRestores - place spills and restores of CSRs
-/// used in MBBs in minimal regions that contain the uses.
-///
-void PEI::placeSpillsAndRestores(MachineFunction &Fn) {
- CSRegBlockMap prevCSRSave;
- CSRegBlockMap prevCSRRestore;
- SmallVector<MachineBasicBlock*, 4> cvBlocks, ncvBlocks;
- bool changed = true;
- unsigned iterations = 0;
-
- // Iterate computation of spill and restore placements in the MCFG until:
- // 1. CSR use info has been fully propagated around the MCFG, and
- // 2. computation of CSRSave[], CSRRestore[] reach fixed points.
- while (changed) {
- changed = false;
- ++iterations;
-
- DEBUG(if (ShrinkWrapDebugging >= Iterations)
- DOUT << "iter " << iterations
- << " --------------------------------------------------\n");
-
- // Calculate CSR{Save,Restore} sets using Antic, Avail on the MCFG,
- // which determines the placements of spills and restores.
- // Keep track of changes to spills, restores in each iteration to
- // minimize the total iterations.
- bool SRChanged = false;
- for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
-
- // Place spills for CSRs in MBB.
- SRChanged |= calcSpillPlacements(MBB, cvBlocks, prevCSRSave);
-
- // Place restores for CSRs in MBB.
- SRChanged |= calcRestorePlacements(MBB, cvBlocks, prevCSRRestore);
- }
-
- // Add uses of CSRs used inside loops where needed.
- changed |= addUsesForTopLevelLoops(cvBlocks);
-
- // Add uses for CSRs spilled or restored at branch, join points.
- if (changed || SRChanged) {
- while (! cvBlocks.empty()) {
- MachineBasicBlock* MBB = cvBlocks.pop_back_val();
- changed |= addUsesForMEMERegion(MBB, ncvBlocks);
- }
- if (! ncvBlocks.empty()) {
- cvBlocks = ncvBlocks;
- ncvBlocks.clear();
- }
- }
-
- if (changed) {
- calculateAnticAvail(Fn);
- CSRSave.clear();
- CSRRestore.clear();
- }
- }
-
- // Check for effectiveness:
- // SR0 = {r | r in CSRSave[EntryBlock], CSRRestore[RB], RB in ReturnBlocks}
- // numSRReduced = |(UsedCSRegs - SR0)|, approx. SR0 by CSRSave[EntryBlock]
- // Gives a measure of how many CSR spills have been moved from EntryBlock
- // to minimal regions enclosing their uses.
- CSRegSet notSpilledInEntryBlock = (UsedCSRegs - CSRSave[EntryBlock]);
- unsigned numSRReducedThisFunc = notSpilledInEntryBlock.count();
- numSRReduced += numSRReducedThisFunc;
- DEBUG(if (ShrinkWrapDebugging >= BasicInfo) {
- DOUT << "-----------------------------------------------------------\n";
- DOUT << "total iterations = " << iterations << " ( "
- << Fn.getFunction()->getName()
- << " " << numSRReducedThisFunc
- << " " << Fn.size()
- << " )\n";
- DOUT << "-----------------------------------------------------------\n";
- dumpSRSets();
- DOUT << "-----------------------------------------------------------\n";
- if (numSRReducedThisFunc)
- verifySpillRestorePlacement();
- });
+#if 0
+void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ if (ShrinkWrapping || ShrinkWrapFunc != "") {
+ AU.addRequired<MachineLoopInfo>();
+ AU.addRequired<MachineDominatorTree>();
+ }
+ AU.addPreserved<MachineLoopInfo>();
+ AU.addPreserved<MachineDominatorTree>();
+ MachineFunctionPass::getAnalysisUsage(AU);
}
+#endif
/// calculateCalleeSavedRegisters - Scan the function for modified callee saved
/// registers. Also calculate the MaxCallFrameSize and HasCalls variables for
@@ -1190,10 +251,6 @@
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
MachineBasicBlock::iterator I;
- DEBUG(if (ShrinkWrapThisFunction && ShrinkWrapDebugging >= Details)
- DOUT << "Inserting CSR spills/restores in function "
- << Fn.getFunction()->getName() << "\n");
-
if (! ShrinkWrapThisFunction) {
// Spill using target interface.
I = EntryBlock->begin();
@@ -1258,10 +315,6 @@
if (save.empty())
continue;
- DEBUG(if (ShrinkWrapDebugging >= Details)
- DOUT << "Spilling " << stringifyCSRegSet(save)
- << " in " << getBasicBlockName(MBB) << "\n");
-
blockCSI.clear();
for (CSRegSet::iterator RI = save.begin(),
RE = save.end(); RI != RE; ++RI) {
@@ -1286,10 +339,6 @@
}
}
- DEBUG(if (ShrinkWrapDebugging >= Details)
- DOUT << "------------------------------"
- << "-----------------------------\n");
-
for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
BE = CSRRestore.end(); BI != BE; ++BI) {
MachineBasicBlock* MBB = BI->first;
@@ -1298,10 +347,6 @@
if (restore.empty())
continue;
- DEBUG(if (ShrinkWrapDebugging >= Details)
- DOUT << "Restoring " << stringifyCSRegSet(restore)
- << " in " << getBasicBlockName(MBB) << "\n");
-
blockCSI.clear();
for (CSRegSet::iterator RI = restore.begin(),
RE = restore.end(); RI != RE; ++RI) {
@@ -1351,10 +396,6 @@
}
}
}
-
- DEBUG(if (ShrinkWrapDebugging >= Details)
- DOUT << "------------------------------"
- << "-----------------------------\n");
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
@@ -1636,284 +677,3 @@
}
}
-// Debugging methods for shrink wrapping.
-#ifndef NDEBUG
-/// findFastExitPath - debugging method used to detect functions
-/// with at least one path from the entry block to a return block
-/// directly or which has a very small number of edges.
-///
-void PEI::findFastExitPath() {
- if (! EntryBlock)
- return;
- // Fina a path from EntryBlock to any return block that does not branch:
- // Entry
- // | ...
- // v |
- // B1<-----+
- // |
- // v
- // Return
- for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(),
- SE = EntryBlock->succ_end(); SI != SE; ++SI) {
- MachineBasicBlock* SUCC = *SI;
-
- // Assume positive, disprove existence of fast path.
-#ifndef NDEBUG
- HasFastExitPath = true;
-#endif
-
- // Check the immediate successors.
- if (isReturnBlock(SUCC)) {
- if (ShrinkWrapDebugging >= BasicInfo)
- DOUT << "Fast exit path: " << getBasicBlockName(EntryBlock)
- << "->" << getBasicBlockName(SUCC) << "\n";
- break;
- }
- // Traverse df from SUCC, look for a branch block.
- std::string exitPath = getBasicBlockName(SUCC);
- for (df_iterator<MachineBasicBlock*> BI = df_begin(SUCC),
- BE = df_end(SUCC); BI != BE; ++BI) {
- MachineBasicBlock* SBB = *BI;
- // Reject paths with branch nodes.
- if (SBB->succ_size() > 1) {
-#ifndef NDEBUG
- HasFastExitPath = false;
-#endif
- break;
- }
- exitPath += "->" + getBasicBlockName(SBB);
- }
-#ifndef NDEBUG
- if (HasFastExitPath) {
-#endif
- if (ShrinkWrapDebugging >= BasicInfo)
- DOUT << "Fast exit path: " << getBasicBlockName(EntryBlock)
- << "->" << exitPath << "\n";
- break;
-#ifndef NDEBUG
- }
-#endif
- }
-}
-
-/// verifySpillRestorePlacement - check the current spill/restore
-/// sets for safety. Attempt to find spills without restores or
-/// restores without spills.
-/// Spills: walk df from each MBB in spill set ensuring that
-/// all CSRs spilled at MMBB are restored on all paths
-/// from MBB to all exit blocks.
-/// Restores: walk idf from each MBB in restore set ensuring that
-/// all CSRs restored at MBB are spilled on all paths
-/// reaching MBB.
-///
-void PEI::verifySpillRestorePlacement() {
- unsigned numReturnBlocks = 0;
- for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- if (isReturnBlock(MBB) || MBB->succ_size() == 0)
- ++numReturnBlocks;
- }
- for (CSRegBlockMap::iterator BI = CSRSave.begin(),
- BE = CSRSave.end(); BI != BE; ++BI) {
- MachineBasicBlock* MBB = BI->first;
- CSRegSet spilled = BI->second;
- CSRegSet restored;
-
- if (spilled.empty())
- continue;
-
- DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(spilled)
- << " RESTORE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
-
- if (CSRRestore[MBB].intersects(spilled)) {
- restored |= (CSRRestore[MBB] & spilled);
- }
-
- // Walk depth first from MBB to find restores of all CSRs spilled at MBB:
- // we must find restores for all spills w/no intervening spills on all
- // paths from MBB to all return blocks.
- for (df_iterator<MachineBasicBlock*> BI = df_begin(MBB),
- BE = df_end(MBB); BI != BE; ++BI) {
- MachineBasicBlock* SBB = *BI;
- if (SBB == MBB)
- continue;
- // Stop when we encounter spills of any CSRs spilled at MBB that
- // have not yet been seen to be restored.
- if (CSRSave[SBB].intersects(spilled) &&
- !restored.contains(CSRSave[SBB] & spilled))
- break;
- // Collect the CSRs spilled at MBB that are restored
- // at this DF successor of MBB.
- if (CSRRestore[SBB].intersects(spilled))
- restored |= (CSRRestore[SBB] & spilled);
- // If we are at a retun block, check that the restores
- // we have seen so far exhaust the spills at MBB, then
- // reset the restores.
- if (isReturnBlock(SBB) || SBB->succ_size() == 0) {
- if (restored != spilled) {
- CSRegSet notRestored = (spilled - restored);
- DOUT << MF->getFunction()->getName() << ": "
- << stringifyCSRegSet(notRestored)
- << " spilled at " << getBasicBlockName(MBB)
- << " are never restored on path to return "
- << getBasicBlockName(SBB) << "\n";
- }
- restored.clear();
- }
- }
- }
-
- // Check restore placements.
- for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
- BE = CSRRestore.end(); BI != BE; ++BI) {
- MachineBasicBlock* MBB = BI->first;
- CSRegSet restored = BI->second;
- CSRegSet spilled;
-
- if (restored.empty())
- continue;
-
- DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRSave[MBB])
- << " RESTORE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(restored) << "\n";
-
- if (CSRSave[MBB].intersects(restored)) {
- spilled |= (CSRSave[MBB] & restored);
- }
- // Walk inverse depth first from MBB to find spills of all
- // CSRs restored at MBB:
- for (idf_iterator<MachineBasicBlock*> BI = idf_begin(MBB),
- BE = idf_end(MBB); BI != BE; ++BI) {
- MachineBasicBlock* PBB = *BI;
- if (PBB == MBB)
- continue;
- // Stop when we encounter restores of any CSRs restored at MBB that
- // have not yet been seen to be spilled.
- if (CSRRestore[PBB].intersects(restored) &&
- !spilled.contains(CSRRestore[PBB] & restored))
- break;
- // Collect the CSRs restored at MBB that are spilled
- // at this DF predecessor of MBB.
- if (CSRSave[PBB].intersects(restored))
- spilled |= (CSRSave[PBB] & restored);
- }
- if (spilled != restored) {
- CSRegSet notSpilled = (restored - spilled);
- DOUT << MF->getFunction()->getName() << ": "
- << stringifyCSRegSet(notSpilled)
- << " restored at " << getBasicBlockName(MBB)
- << " are never spilled\n";
- }
- }
-}
-
-// Debugging print methods.
-std::string PEI::getBasicBlockName(const MachineBasicBlock* MBB) {
- std::ostringstream name;
- if (MBB) {
- if (MBB->getBasicBlock())
- name << MBB->getBasicBlock()->getName();
- else
- name << "_MBB_" << MBB->getNumber();
- }
- return name.str();
-}
-
-std::string PEI::stringifyCSRegSet(const CSRegSet& s) {
- const TargetRegisterInfo* TRI = MF->getTarget().getRegisterInfo();
- const std::vector<CalleeSavedInfo> CSI =
- MF->getFrameInfo()->getCalleeSavedInfo();
-
- std::ostringstream srep;
- if (CSI.size() == 0) {
- srep << "[]";
- return srep.str();
- }
- srep << "[";
- CSRegSet::iterator I = s.begin(), E = s.end();
- if (I != E) {
- unsigned reg = CSI[*I].getReg();
- srep << TRI->getName(reg);
- for (++I; I != E; ++I) {
- reg = CSI[*I].getReg();
- srep << ",";
- srep << TRI->getName(reg);
- }
- }
- srep << "]";
- return srep.str();
-}
-
-void PEI::dumpSet(const CSRegSet& s) {
- DOUT << stringifyCSRegSet(s) << "\n";
-}
-
-void PEI::dumpUsed(MachineBasicBlock* MBB) {
- if (MBB) {
- DOUT << "CSRUsed[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRUsed[MBB]) << "\n";
- }
-}
-
-void PEI::dumpAllUsed() {
- for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- dumpUsed(MBB);
- }
-}
-
-void PEI::dumpSets(MachineBasicBlock* MBB) {
- if (MBB) {
- DOUT << getBasicBlockName(MBB) << " | "
- << stringifyCSRegSet(CSRUsed[MBB]) << " | "
- << stringifyCSRegSet(AnticIn[MBB]) << " | "
- << stringifyCSRegSet(AnticOut[MBB]) << " | "
- << stringifyCSRegSet(AvailIn[MBB]) << " | "
- << stringifyCSRegSet(AvailOut[MBB]) << "\n";
- }
-}
-
-void PEI::dumpSets1(MachineBasicBlock* MBB) {
- if (MBB) {
- DOUT << getBasicBlockName(MBB) << " | "
- << stringifyCSRegSet(CSRUsed[MBB]) << " | "
- << stringifyCSRegSet(AnticIn[MBB]) << " | "
- << stringifyCSRegSet(AnticOut[MBB]) << " | "
- << stringifyCSRegSet(AvailIn[MBB]) << " | "
- << stringifyCSRegSet(AvailOut[MBB]) << " | "
- << stringifyCSRegSet(CSRSave[MBB]) << " | "
- << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
- }
-}
-
-void PEI::dumpAllSets() {
- for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
- MBBI != MBBE; ++MBBI) {
- MachineBasicBlock* MBB = MBBI;
- dumpSets1(MBB);
- }
-}
-
-void PEI::dumpSRSets() {
- for (MachineFunction::iterator MBB = MF->begin(), E = MF->end();
- MBB != E; ++MBB) {
- if (! CSRSave[MBB].empty()) {
- DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRSave[MBB]);
- if (CSRRestore[MBB].empty())
- DOUT << "\n";
- }
- if (! CSRRestore[MBB].empty()) {
- if (! CSRSave[MBB].empty())
- DOUT << " ";
- DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
- << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
- }
- }
-}
-#endif
Added: llvm/trunk/lib/CodeGen/ShrinkWrapping.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ShrinkWrapping.cpp?rev=71588&view=auto
==============================================================================
--- llvm/trunk/lib/CodeGen/ShrinkWrapping.cpp (added)
+++ llvm/trunk/lib/CodeGen/ShrinkWrapping.cpp Tue May 12 15:33:29 2009
@@ -0,0 +1,1141 @@
+//===-- ShrinkWrapping.cpp - Reduce spills/restores of callee-saved regs --===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a shrink wrapping variant of prolog/epilog insertion:
+// - Spills and restores of callee-saved registers (CSRs) are placed in the
+// machine CFG to tightly surround their uses so that execution paths that
+// do not use CSRs do not pay the spill/restore penalty.
+//
+// - Avoiding placment of spills/restores in loops: if a CSR is used inside a
+// loop the spills are placed in the loop preheader, and restores are
+// placed in the loop exit nodes (the successors of loop _exiting_ nodes).
+//
+// - Covering paths without CSR uses:
+// If a region in a CFG uses CSRs and has multiple entry and/or exit points,
+// the use info for the CSRs inside the region is propagated outward in the
+// CFG to ensure validity of the spill/restore placements. This decreases
+// the effectiveness of shrink wrapping but does not require edge splitting
+// in the machine CFG.
+//
+// This shrink wrapping implementation uses an iterative analysis to determine
+// which basic blocks require spills and restores for CSRs.
+//
+// This pass uses MachineDominators and MachineLoopInfo. Loop information
+// is used to prevent placement of callee-saved register spills/restores
+// in the bodies of loops.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "shrink-wrap"
+
+#include "PEI.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Statistic.h"
+#include <sstream>
+
+using namespace llvm;
+
+STATISTIC(numSRReduced, "Number of CSR spills+restores reduced.");
+
+// Shrink Wrapping:
+static cl::opt<bool>
+ShrinkWrapping("shrink-wrap",
+ cl::desc("Shrink wrap callee-saved register spills/restores"));
+
+// Shrink wrap only the specified function, a debugging aid.
+static cl::opt<std::string>
+ShrinkWrapFunc("shrink-wrap-func", cl::Hidden,
+ cl::desc("Shrink wrap the specified function"),
+ cl::value_desc("funcname"),
+ cl::init(""));
+
+// Debugging level for shrink wrapping.
+enum ShrinkWrapDebugLevel {
+ None, BasicInfo, Iterations, Details
+};
+
+static cl::opt<enum ShrinkWrapDebugLevel>
+ShrinkWrapDebugging("shrink-wrap-dbg", cl::Hidden,
+ cl::desc("Print shrink wrapping debugging information"),
+ cl::values(
+ clEnumVal(None , "disable debug output"),
+ clEnumVal(BasicInfo , "print basic DF sets"),
+ clEnumVal(Iterations, "print SR sets for each iteration"),
+ clEnumVal(Details , "print all DF sets"),
+ clEnumValEnd));
+
+
+void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ if (ShrinkWrapping || ShrinkWrapFunc != "") {
+ AU.addRequired<MachineLoopInfo>();
+ AU.addRequired<MachineDominatorTree>();
+ }
+ AU.addPreserved<MachineLoopInfo>();
+ AU.addPreserved<MachineDominatorTree>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+//===----------------------------------------------------------------------===//
+// ShrinkWrapping implementation
+//===----------------------------------------------------------------------===//
+
+// Convienences for dealing with machine loops.
+MachineBasicBlock* PEI::getTopLevelLoopPreheader(MachineLoop* LP) {
+ assert(LP && "Machine loop is NULL.");
+ MachineBasicBlock* PHDR = LP->getLoopPreheader();
+ MachineLoop* PLP = LP->getParentLoop();
+ while (PLP) {
+ PHDR = PLP->getLoopPreheader();
+ PLP = PLP->getParentLoop();
+ }
+ return PHDR;
+}
+
+MachineLoop* PEI::getTopLevelLoopParent(MachineLoop *LP) {
+ if (LP == 0)
+ return 0;
+ MachineLoop* PLP = LP->getParentLoop();
+ while (PLP) {
+ LP = PLP;
+ PLP = PLP->getParentLoop();
+ }
+ return LP;
+}
+
+bool PEI::isReturnBlock(MachineBasicBlock* MBB) {
+ return (MBB && !MBB->empty() && MBB->back().getDesc().isReturn());
+}
+
+// Initialize shrink wrapping DFA sets, called before iterations.
+void PEI::clearAnticAvailSets() {
+ AnticIn.clear();
+ AnticOut.clear();
+ AvailIn.clear();
+ AvailOut.clear();
+}
+
+// Clear all sets constructed by shrink wrapping.
+void PEI::clearAllSets() {
+ ReturnBlocks.clear();
+ clearAnticAvailSets();
+ UsedCSRegs.clear();
+ CSRUsed.clear();
+ TLLoops.clear();
+ CSRSave.clear();
+ CSRRestore.clear();
+}
+
+// Initialize all shrink wrapping data.
+void PEI::initShrinkWrappingInfo() {
+ clearAllSets();
+ EntryBlock = 0;
+#ifndef NDEBUG
+ HasFastExitPath = false;
+#endif
+ ShrinkWrapThisFunction = ShrinkWrapping;
+ // DEBUG: enable or disable shrink wrapping for the current function
+ // via --shrink-wrap-func=<funcname>.
+#ifndef NDEBUG
+ if (ShrinkWrapFunc != "") {
+ std::string MFName = MF->getFunction()->getName();
+ ShrinkWrapThisFunction = (MFName == ShrinkWrapFunc);
+ }
+#endif
+}
+
+
+/// placeCSRSpillsAndRestores - determine which MBBs of the function
+/// need save, restore code for callee-saved registers by doing a DF analysis
+/// similar to the one used in code motion (GVNPRE). This produces maps of MBBs
+/// to sets of registers (CSRs) for saves and restores. MachineLoopInfo
+/// is used to ensure that CSR save/restore code is not placed inside loops.
+/// This function computes the maps of MBBs -> CSRs to spill and restore
+/// in CSRSave, CSRRestore.
+///
+/// If shrink wrapping is not being performed, place all spills in
+/// the entry block, all restores in return blocks. In this case,
+/// CSRSave has a single mapping, CSRRestore has mappings for each
+/// return block.
+///
+void PEI::placeCSRSpillsAndRestores(MachineFunction &Fn) {
+
+ DEBUG(MF = &Fn);
+
+ initShrinkWrappingInfo();
+
+ DEBUG(if (ShrinkWrapThisFunction) {
+ DOUT << "Place CSR spills/restores for "
+ << MF->getFunction()->getName() << "\n";
+ });
+
+ if (calculateSets(Fn))
+ placeSpillsAndRestores(Fn);
+}
+
+/// calcAnticInOut - calculate the anticipated in/out reg sets
+/// for the given MBB by looking forward in the MCFG at MBB's
+/// successors.
+///
+bool PEI::calcAnticInOut(MachineBasicBlock* MBB) {
+ bool changed = false;
+
+ // AnticOut[MBB] = INTERSECT(AnticIn[S] for S in SUCCESSORS(MBB))
+ SmallVector<MachineBasicBlock*, 4> successors;
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ SE = MBB->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+ if (SUCC != MBB)
+ successors.push_back(SUCC);
+ }
+
+ unsigned i = 0, e = successors.size();
+ if (i != e) {
+ CSRegSet prevAnticOut = AnticOut[MBB];
+ MachineBasicBlock* SUCC = successors[i];
+
+ AnticOut[MBB] = AnticIn[SUCC];
+ for (++i; i != e; ++i) {
+ SUCC = successors[i];
+ AnticOut[MBB] &= AnticIn[SUCC];
+ }
+ if (prevAnticOut != AnticOut[MBB])
+ changed = true;
+ }
+
+ // AnticIn[MBB] = UNION(CSRUsed[MBB], AnticOut[MBB]);
+ CSRegSet prevAnticIn = AnticIn[MBB];
+ AnticIn[MBB] = CSRUsed[MBB] | AnticOut[MBB];
+ if (prevAnticIn |= AnticIn[MBB])
+ changed = true;
+ return changed;
+}
+
+/// calcAvailInOut - calculate the available in/out reg sets
+/// for the given MBB by looking backward in the MCFG at MBB's
+/// predecessors.
+///
+bool PEI::calcAvailInOut(MachineBasicBlock* MBB) {
+ bool changed = false;
+
+ // AvailIn[MBB] = INTERSECT(AvailOut[P] for P in PREDECESSORS(MBB))
+ SmallVector<MachineBasicBlock*, 4> predecessors;
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ MachineBasicBlock* PRED = *PI;
+ if (PRED != MBB)
+ predecessors.push_back(PRED);
+ }
+
+ unsigned i = 0, e = predecessors.size();
+ if (i != e) {
+ CSRegSet prevAvailIn = AvailIn[MBB];
+ MachineBasicBlock* PRED = predecessors[i];
+
+ AvailIn[MBB] = AvailOut[PRED];
+ for (++i; i != e; ++i) {
+ PRED = predecessors[i];
+ AvailIn[MBB] &= AvailOut[PRED];
+ }
+ if (prevAvailIn != AvailIn[MBB])
+ changed = true;
+ }
+
+ // AvailOut[MBB] = UNION(CSRUsed[MBB], AvailIn[MBB]);
+ CSRegSet prevAvailOut = AvailOut[MBB];
+ AvailOut[MBB] = CSRUsed[MBB] | AvailIn[MBB];
+ if (prevAvailOut |= AvailOut[MBB])
+ changed = true;
+ return changed;
+}
+
+/// calculateAnticAvail - build the sets anticipated and available
+/// registers in the MCFG of the current function iteratively,
+/// doing a combined forward and backward analysis.
+///
+void PEI::calculateAnticAvail(MachineFunction &Fn) {
+ // Initialize data flow sets.
+ clearAnticAvailSets();
+
+ // Calulate Antic{In,Out} and Avail{In,Out} iteratively on the MCFG.
+ bool changed = true;
+ unsigned iterations = 0;
+ while (changed) {
+ changed = false;
+ ++iterations;
+ for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+
+ // Calculate anticipated in, out regs at MBB from
+ // anticipated at successors of MBB.
+ changed |= calcAnticInOut(MBB);
+
+ // Calculate available in, out regs at MBB from
+ // available at predecessors of MBB.
+ changed |= calcAvailInOut(MBB);
+ }
+ }
+
+ DEBUG(if (ShrinkWrapDebugging >= Details) {
+ DOUT << "-----------------------------------------------------------\n";
+ DOUT << " Antic/Avail Sets:\n";
+ DOUT << "-----------------------------------------------------------\n";
+ DOUT << "iterations = " << iterations << "\n";
+ DOUT << "-----------------------------------------------------------\n";
+ DOUT << "MBB | USED | ANTIC_IN | ANTIC_OUT | AVAIL_IN | AVAIL_OUT\n";
+ DOUT << "-----------------------------------------------------------\n";
+ for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ dumpSets(MBB);
+ }
+ DOUT << "-----------------------------------------------------------\n";
+ });
+}
+
+/// propagateUsesAroundLoop - copy used register info from MBB to all blocks
+/// of the loop given by LP and its parent loops. This prevents spills/restores
+/// from being placed in the bodies of loops.
+///
+void PEI::propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP) {
+ if (! MBB || !LP)
+ return;
+
+ std::vector<MachineBasicBlock*> loopBlocks = LP->getBlocks();
+ for (unsigned i = 0, e = loopBlocks.size(); i != e; ++i) {
+ MachineBasicBlock* LBB = loopBlocks[i];
+ if (LBB == MBB)
+ continue;
+ if (CSRUsed[LBB].contains(CSRUsed[MBB]))
+ continue;
+ CSRUsed[LBB] |= CSRUsed[MBB];
+ }
+}
+
+/// calculateSets - collect the CSRs used in this function, compute
+/// the DF sets that describe the initial minimal regions in the
+/// Machine CFG around which CSR spills and restores must be placed.
+///
+/// Additionally, this function decides if shrink wrapping should
+/// be disabled for the current function, checking the following:
+/// 1. the current function has more than 500 MBBs: heuristic limit
+/// on function size to reduce compile time impact of the current
+/// iterative algorithm.
+/// 2. all CSRs are used in the entry block.
+/// 3. all CSRs are used in all immediate successors of the entry block.
+/// 4. all CSRs are used in a subset of blocks, each of which dominates
+/// all return blocks. These blocks, taken as a subgraph of the MCFG,
+/// are equivalent to the entry block since all execution paths pass
+/// through them.
+///
+bool PEI::calculateSets(MachineFunction &Fn) {
+ // Sets used to compute spill, restore placement sets.
+ const std::vector<CalleeSavedInfo> CSI =
+ Fn.getFrameInfo()->getCalleeSavedInfo();
+
+ // If no CSRs used, we are done.
+ if (CSI.empty()) {
+ DEBUG(if (ShrinkWrapThisFunction)
+ DOUT << "DISABLED: " << Fn.getFunction()->getName()
+ << ": uses no callee-saved registers\n");
+ return false;
+ }
+
+ // Save refs to entry and return blocks.
+ EntryBlock = Fn.begin();
+ for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end();
+ MBB != E; ++MBB)
+ if (isReturnBlock(MBB))
+ ReturnBlocks.push_back(MBB);
+
+ // Determine if this function has fast exit paths.
+ DEBUG(if (ShrinkWrapThisFunction)
+ findFastExitPath());
+
+ // Limit shrink wrapping via the current iterative bit vector
+ // implementation to functions with <= 500 MBBs.
+ if (Fn.size() > 500) {
+ DEBUG(if (ShrinkWrapThisFunction)
+ DOUT << "DISABLED: " << Fn.getFunction()->getName()
+ << ": too large (" << Fn.size() << " MBBs)\n");
+ ShrinkWrapThisFunction = false;
+ }
+
+ // Return now if not shrink wrapping.
+ if (! ShrinkWrapThisFunction)
+ return false;
+
+ // Collect set of used CSRs.
+ for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
+ UsedCSRegs.set(inx);
+ }
+
+ // Walk instructions in all MBBs, create CSRUsed[] sets, choose
+ // whether or not to shrink wrap this function.
+ MachineLoopInfo &LI = getAnalysis<MachineLoopInfo>();
+ MachineDominatorTree &DT = getAnalysis<MachineDominatorTree>();
+ const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
+
+ bool allCSRUsesInEntryBlock = true;
+ for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ for (MachineBasicBlock::iterator I = MBB->begin(); I != MBB->end(); ++I) {
+ for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) {
+ unsigned Reg = CSI[inx].getReg();
+ // If instruction I reads or modifies Reg, add it to UsedCSRegs,
+ // CSRUsed map for the current block.
+ for (unsigned opInx = 0, opEnd = I->getNumOperands();
+ opInx != opEnd; ++opInx) {
+ const MachineOperand &MO = I->getOperand(opInx);
+ if (! (MO.isReg() && (MO.isUse() || MO.isDef())))
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (MOReg == Reg ||
+ (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
+ TargetRegisterInfo::isPhysicalRegister(Reg) &&
+ TRI->isSubRegister(Reg, MOReg))) {
+ // CSR Reg is defined/used in block MBB.
+ CSRUsed[MBB].set(inx);
+ // Check for uses in EntryBlock.
+ if (MBB != EntryBlock)
+ allCSRUsesInEntryBlock = false;
+ }
+ }
+ }
+ }
+
+ if (CSRUsed[MBB].empty())
+ continue;
+
+ // Propagate CSRUsed[MBB] in loops
+ if (MachineLoop* LP = LI.getLoopFor(MBB)) {
+ // Add top level loop to work list.
+ MachineBasicBlock* HDR = getTopLevelLoopPreheader(LP);
+ MachineLoop* PLP = getTopLevelLoopParent(LP);
+
+ if (! HDR) {
+ HDR = PLP->getHeader();
+ assert(HDR->pred_size() > 0 && "Loop header has no predecessors?");
+ MachineBasicBlock::pred_iterator PI = HDR->pred_begin();
+ HDR = *PI;
+ }
+ TLLoops[HDR] = PLP;
+
+ // Push uses from inside loop to its parent loops,
+ // or to all other MBBs in its loop.
+ if (LP->getLoopDepth() > 1) {
+ for (MachineLoop* PLP = LP->getParentLoop(); PLP;
+ PLP = PLP->getParentLoop()) {
+ propagateUsesAroundLoop(MBB, PLP);
+ }
+ } else {
+ propagateUsesAroundLoop(MBB, LP);
+ }
+ }
+ }
+
+ if (allCSRUsesInEntryBlock) {
+ DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
+ << ": all CSRs used in EntryBlock\n");
+ ShrinkWrapThisFunction = false;
+ } else {
+ bool allCSRsUsedInEntryFanout = true;
+ for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(),
+ SE = EntryBlock->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+ if (CSRUsed[SUCC] != UsedCSRegs)
+ allCSRsUsedInEntryFanout = false;
+ }
+ if (allCSRsUsedInEntryFanout) {
+ DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
+ << ": all CSRs used in imm successors of EntryBlock\n");
+ ShrinkWrapThisFunction = false;
+ }
+ }
+
+ if (ShrinkWrapThisFunction) {
+ // Check if MBB uses CSRs and dominates all exit nodes.
+ // Such nodes are equiv. to the entry node w.r.t.
+ // CSR uses: every path through the function must
+ // pass through this node. If each CSR is used at least
+ // once by these nodes, shrink wrapping is disabled.
+ CSRegSet CSRUsedInChokePoints;
+ for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ if (MBB == EntryBlock || CSRUsed[MBB].empty() || MBB->succ_size() < 1)
+ continue;
+ bool dominatesExitNodes = true;
+ for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
+ if (! DT.dominates(MBB, ReturnBlocks[ri])) {
+ dominatesExitNodes = false;
+ break;
+ }
+ if (dominatesExitNodes) {
+ CSRUsedInChokePoints |= CSRUsed[MBB];
+ if (CSRUsedInChokePoints == UsedCSRegs) {
+ DEBUG(DOUT << "DISABLED: " << Fn.getFunction()->getName()
+ << ": all CSRs used in choke point(s) at "
+ << getBasicBlockName(MBB) << "\n");
+ ShrinkWrapThisFunction = false;
+ break;
+ }
+ }
+ }
+ }
+
+ // Return now if we have decided not to apply shrink wrapping
+ // to the current function.
+ if (! ShrinkWrapThisFunction)
+ return false;
+
+ DEBUG({
+ DOUT << "ENABLED: " << Fn.getFunction()->getName();
+ if (HasFastExitPath)
+ DOUT << " (fast exit path)";
+ DOUT << "\n";
+ if (ShrinkWrapDebugging >= BasicInfo) {
+ DOUT << "------------------------------"
+ << "-----------------------------\n";
+ DOUT << "UsedCSRegs = " << stringifyCSRegSet(UsedCSRegs) << "\n";
+ if (ShrinkWrapDebugging >= Details) {
+ DOUT << "------------------------------"
+ << "-----------------------------\n";
+ dumpAllUsed();
+ }
+ }
+ });
+
+ // Build initial DF sets to determine minimal regions in the
+ // Machine CFG around which CSRs must be spilled and restored.
+ calculateAnticAvail(Fn);
+
+ return true;
+}
+
+/// addUsesForMEMERegion - add uses of CSRs spilled or restored in
+/// multi-entry, multi-exit (MEME) regions so spill and restore
+/// placement will not break code that enters or leaves a
+/// shrink-wrapped region by inducing spills with no matching
+/// restores or restores with no matching spills. A MEME region
+/// is a subgraph of the MCFG with multiple entry edges, multiple
+/// exit edges, or both. This code propagates use information
+/// through the MCFG until all paths requiring spills and restores
+/// _outside_ the computed minimal placement regions have been covered.
+///
+bool PEI::addUsesForMEMERegion(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4>& blks) {
+ if (MBB->succ_size() < 2 && MBB->pred_size() < 2) {
+ bool processThisBlock = false;
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ SE = MBB->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+ if (SUCC->pred_size() > 1) {
+ processThisBlock = true;
+ break;
+ }
+ }
+ if (!CSRRestore[MBB].empty() && MBB->succ_size() > 0) {
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ MachineBasicBlock* PRED = *PI;
+ if (PRED->succ_size() > 1) {
+ processThisBlock = true;
+ break;
+ }
+ }
+ }
+ if (! processThisBlock)
+ return false;
+ }
+
+ CSRegSet prop;
+ if (!CSRSave[MBB].empty())
+ prop = CSRSave[MBB];
+ else if (!CSRRestore[MBB].empty())
+ prop = CSRRestore[MBB];
+ else
+ prop = CSRUsed[MBB];
+ if (prop.empty())
+ return false;
+
+ // Propagate selected bits to successors, predecessors of MBB.
+ bool addedUses = false;
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ SE = MBB->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+ // Self-loop
+ if (SUCC == MBB)
+ continue;
+ if (! CSRUsed[SUCC].contains(prop)) {
+ CSRUsed[SUCC] |= prop;
+ addedUses = true;
+ blks.push_back(SUCC);
+ DEBUG(if (ShrinkWrapDebugging >= Iterations)
+ DOUT << getBasicBlockName(MBB)
+ << "(" << stringifyCSRegSet(prop) << ")->"
+ << "successor " << getBasicBlockName(SUCC) << "\n");
+ }
+ }
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ MachineBasicBlock* PRED = *PI;
+ // Self-loop
+ if (PRED == MBB)
+ continue;
+ if (! CSRUsed[PRED].contains(prop)) {
+ CSRUsed[PRED] |= prop;
+ addedUses = true;
+ blks.push_back(PRED);
+ DEBUG(if (ShrinkWrapDebugging >= Iterations)
+ DOUT << getBasicBlockName(MBB)
+ << "(" << stringifyCSRegSet(prop) << ")->"
+ << "predecessor " << getBasicBlockName(PRED) << "\n");
+ }
+ }
+ return addedUses;
+}
+
+/// addUsesForTopLevelLoops - add uses for CSRs used inside top
+/// level loops to the exit blocks of those loops.
+///
+bool PEI::addUsesForTopLevelLoops(SmallVector<MachineBasicBlock*, 4>& blks) {
+ bool addedUses = false;
+
+ // Place restores for top level loops where needed.
+ for (DenseMap<MachineBasicBlock*, MachineLoop*>::iterator
+ I = TLLoops.begin(), E = TLLoops.end(); I != E; ++I) {
+ MachineBasicBlock* MBB = I->first;
+ MachineLoop* LP = I->second;
+ MachineBasicBlock* HDR = LP->getHeader();
+ SmallVector<MachineBasicBlock*, 4> exitBlocks;
+ CSRegSet loopSpills;
+
+ loopSpills = CSRSave[MBB];
+ if (CSRSave[MBB].empty()) {
+ loopSpills = CSRUsed[HDR];
+ assert(!loopSpills.empty() && "No CSRs used in loop?");
+ } else if (CSRRestore[MBB].contains(CSRSave[MBB]))
+ continue;
+
+ LP->getExitBlocks(exitBlocks);
+ assert(exitBlocks.size() > 0 && "Loop has no top level exit blocks?");
+ for (unsigned i = 0, e = exitBlocks.size(); i != e; ++i) {
+ MachineBasicBlock* EXB = exitBlocks[i];
+ if (! CSRUsed[EXB].contains(loopSpills)) {
+ CSRUsed[EXB] |= loopSpills;
+ addedUses = true;
+ DEBUG(if (ShrinkWrapDebugging >= Iterations)
+ DOUT << "LOOP " << getBasicBlockName(MBB)
+ << "(" << stringifyCSRegSet(loopSpills) << ")->"
+ << getBasicBlockName(EXB) << "\n");
+ if (EXB->succ_size() > 1 || EXB->pred_size() > 1)
+ blks.push_back(EXB);
+ }
+ }
+ }
+ return addedUses;
+}
+
+/// calcSpillPlacements - determine which CSRs should be spilled
+/// in MBB using AnticIn sets of MBB's predecessors, keeping track
+/// of changes to spilled reg sets. Add MBB to the set of blocks
+/// that need to be processed for propagating use info to cover
+/// multi-entry/exit regions.
+///
+bool PEI::calcSpillPlacements(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4> &blks,
+ CSRegBlockMap &prevSpills) {
+ bool placedSpills = false;
+ // Intersect (CSRegs - AnticIn[P]) for P in Predecessors(MBB)
+ CSRegSet anticInPreds;
+ SmallVector<MachineBasicBlock*, 4> predecessors;
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ MachineBasicBlock* PRED = *PI;
+ if (PRED != MBB)
+ predecessors.push_back(PRED);
+ }
+ unsigned i = 0, e = predecessors.size();
+ if (i != e) {
+ MachineBasicBlock* PRED = predecessors[i];
+ anticInPreds = UsedCSRegs - AnticIn[PRED];
+ for (++i; i != e; ++i) {
+ PRED = predecessors[i];
+ anticInPreds &= (UsedCSRegs - AnticIn[PRED]);
+ }
+ } else {
+ // Handle uses in entry blocks (which have no predecessors).
+ // This is necessary because the DFA formulation assumes the
+ // entry and (multiple) exit nodes cannot have CSR uses, which
+ // is not the case in the real world.
+ anticInPreds = UsedCSRegs;
+ }
+ // Compute spills required at MBB:
+ CSRSave[MBB] |= (AnticIn[MBB] - AvailIn[MBB]) & anticInPreds;
+
+ if (! CSRSave[MBB].empty()) {
+ if (MBB == EntryBlock) {
+ for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri)
+ CSRRestore[ReturnBlocks[ri]] |= CSRSave[MBB];
+ } else {
+ // Reset all regs spilled in MBB that are also spilled in EntryBlock.
+ if (CSRSave[EntryBlock].intersects(CSRSave[MBB])) {
+ CSRSave[MBB] = CSRSave[MBB] - CSRSave[EntryBlock];
+ }
+ }
+ }
+ placedSpills = (CSRSave[MBB] != prevSpills[MBB]);
+ prevSpills[MBB] = CSRSave[MBB];
+ // Remember this block for adding restores to successor
+ // blocks for multi-entry region.
+ if (placedSpills)
+ blks.push_back(MBB);
+
+ DEBUG(if (! CSRSave[MBB].empty() && ShrinkWrapDebugging >= Iterations)
+ DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRSave[MBB]) << "\n");
+
+ return placedSpills;
+}
+
+/// calcRestorePlacements - determine which CSRs should be restored
+/// in MBB using AvailOut sets of MBB's succcessors, keeping track
+/// of changes to restored reg sets. Add MBB to the set of blocks
+/// that need to be processed for propagating use info to cover
+/// multi-entry/exit regions.
+///
+bool PEI::calcRestorePlacements(MachineBasicBlock* MBB,
+ SmallVector<MachineBasicBlock*, 4> &blks,
+ CSRegBlockMap &prevRestores) {
+ bool placedRestores = false;
+ // Intersect (CSRegs - AvailOut[S]) for S in Successors(MBB)
+ CSRegSet availOutSucc;
+ SmallVector<MachineBasicBlock*, 4> successors;
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ SE = MBB->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+ if (SUCC != MBB)
+ successors.push_back(SUCC);
+ }
+ unsigned i = 0, e = successors.size();
+ if (i != e) {
+ MachineBasicBlock* SUCC = successors[i];
+ availOutSucc = UsedCSRegs - AvailOut[SUCC];
+ for (++i; i != e; ++i) {
+ SUCC = successors[i];
+ availOutSucc &= (UsedCSRegs - AvailOut[SUCC]);
+ }
+ } else {
+ if (! CSRUsed[MBB].empty() || ! AvailOut[MBB].empty()) {
+ // Handle uses in return blocks (which have no successors).
+ // This is necessary because the DFA formulation assumes the
+ // entry and (multiple) exit nodes cannot have CSR uses, which
+ // is not the case in the real world.
+ availOutSucc = UsedCSRegs;
+ }
+ }
+ // Compute restores required at MBB:
+ CSRRestore[MBB] |= (AvailOut[MBB] - AnticOut[MBB]) & availOutSucc;
+
+ // Postprocess restore placements at MBB.
+ // Remove the CSRs that are restored in the return blocks.
+ // Lest this be confusing, note that:
+ // CSRSave[EntryBlock] == CSRRestore[B] for all B in ReturnBlocks.
+ if (MBB->succ_size() && ! CSRRestore[MBB].empty()) {
+ if (! CSRSave[EntryBlock].empty())
+ CSRRestore[MBB] = CSRRestore[MBB] - CSRSave[EntryBlock];
+ }
+ placedRestores = (CSRRestore[MBB] != prevRestores[MBB]);
+ prevRestores[MBB] = CSRRestore[MBB];
+ // Remember this block for adding saves to predecessor
+ // blocks for multi-entry region.
+ if (placedRestores)
+ blks.push_back(MBB);
+
+ DEBUG(if (! CSRRestore[MBB].empty() && ShrinkWrapDebugging >= Iterations)
+ DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRRestore[MBB]) << "\n");
+
+ return placedRestores;
+}
+
+/// placeSpillsAndRestores - place spills and restores of CSRs
+/// used in MBBs in minimal regions that contain the uses.
+///
+void PEI::placeSpillsAndRestores(MachineFunction &Fn) {
+ CSRegBlockMap prevCSRSave;
+ CSRegBlockMap prevCSRRestore;
+ SmallVector<MachineBasicBlock*, 4> cvBlocks, ncvBlocks;
+ bool changed = true;
+ unsigned iterations = 0;
+
+ // Iterate computation of spill and restore placements in the MCFG until:
+ // 1. CSR use info has been fully propagated around the MCFG, and
+ // 2. computation of CSRSave[], CSRRestore[] reach fixed points.
+ while (changed) {
+ changed = false;
+ ++iterations;
+
+ DEBUG(if (ShrinkWrapDebugging >= Iterations)
+ DOUT << "iter " << iterations
+ << " --------------------------------------------------\n");
+
+ // Calculate CSR{Save,Restore} sets using Antic, Avail on the MCFG,
+ // which determines the placements of spills and restores.
+ // Keep track of changes to spills, restores in each iteration to
+ // minimize the total iterations.
+ bool SRChanged = false;
+ for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+
+ // Place spills for CSRs in MBB.
+ SRChanged |= calcSpillPlacements(MBB, cvBlocks, prevCSRSave);
+
+ // Place restores for CSRs in MBB.
+ SRChanged |= calcRestorePlacements(MBB, cvBlocks, prevCSRRestore);
+ }
+
+ // Add uses of CSRs used inside loops where needed.
+ changed |= addUsesForTopLevelLoops(cvBlocks);
+
+ // Add uses for CSRs spilled or restored at branch, join points.
+ if (changed || SRChanged) {
+ while (! cvBlocks.empty()) {
+ MachineBasicBlock* MBB = cvBlocks.pop_back_val();
+ changed |= addUsesForMEMERegion(MBB, ncvBlocks);
+ }
+ if (! ncvBlocks.empty()) {
+ cvBlocks = ncvBlocks;
+ ncvBlocks.clear();
+ }
+ }
+
+ if (changed) {
+ calculateAnticAvail(Fn);
+ CSRSave.clear();
+ CSRRestore.clear();
+ }
+ }
+
+ // Check for effectiveness:
+ // SR0 = {r | r in CSRSave[EntryBlock], CSRRestore[RB], RB in ReturnBlocks}
+ // numSRReduced = |(UsedCSRegs - SR0)|, approx. SR0 by CSRSave[EntryBlock]
+ // Gives a measure of how many CSR spills have been moved from EntryBlock
+ // to minimal regions enclosing their uses.
+ CSRegSet notSpilledInEntryBlock = (UsedCSRegs - CSRSave[EntryBlock]);
+ unsigned numSRReducedThisFunc = notSpilledInEntryBlock.count();
+ numSRReduced += numSRReducedThisFunc;
+ DEBUG(if (ShrinkWrapDebugging >= BasicInfo) {
+ DOUT << "-----------------------------------------------------------\n";
+ DOUT << "total iterations = " << iterations << " ( "
+ << Fn.getFunction()->getName()
+ << " " << numSRReducedThisFunc
+ << " " << Fn.size()
+ << " )\n";
+ DOUT << "-----------------------------------------------------------\n";
+ dumpSRSets();
+ DOUT << "-----------------------------------------------------------\n";
+ if (numSRReducedThisFunc)
+ verifySpillRestorePlacement();
+ });
+}
+
+// Debugging methods.
+#ifndef NDEBUG
+/// findFastExitPath - debugging method used to detect functions
+/// with at least one path from the entry block to a return block
+/// directly or which has a very small number of edges.
+///
+void PEI::findFastExitPath() {
+ if (! EntryBlock)
+ return;
+ // Fina a path from EntryBlock to any return block that does not branch:
+ // Entry
+ // | ...
+ // v |
+ // B1<-----+
+ // |
+ // v
+ // Return
+ for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(),
+ SE = EntryBlock->succ_end(); SI != SE; ++SI) {
+ MachineBasicBlock* SUCC = *SI;
+
+ // Assume positive, disprove existence of fast path.
+ HasFastExitPath = true;
+
+ // Check the immediate successors.
+ if (isReturnBlock(SUCC)) {
+ if (ShrinkWrapDebugging >= BasicInfo)
+ DOUT << "Fast exit path: " << getBasicBlockName(EntryBlock)
+ << "->" << getBasicBlockName(SUCC) << "\n";
+ break;
+ }
+ // Traverse df from SUCC, look for a branch block.
+ std::string exitPath = getBasicBlockName(SUCC);
+ for (df_iterator<MachineBasicBlock*> BI = df_begin(SUCC),
+ BE = df_end(SUCC); BI != BE; ++BI) {
+ MachineBasicBlock* SBB = *BI;
+ // Reject paths with branch nodes.
+ if (SBB->succ_size() > 1) {
+ HasFastExitPath = false;
+ break;
+ }
+ exitPath += "->" + getBasicBlockName(SBB);
+ }
+ if (HasFastExitPath) {
+ if (ShrinkWrapDebugging >= BasicInfo)
+ DOUT << "Fast exit path: " << getBasicBlockName(EntryBlock)
+ << "->" << exitPath << "\n";
+ break;
+ }
+ }
+}
+
+/// verifySpillRestorePlacement - check the current spill/restore
+/// sets for safety. Attempt to find spills without restores or
+/// restores without spills.
+/// Spills: walk df from each MBB in spill set ensuring that
+/// all CSRs spilled at MMBB are restored on all paths
+/// from MBB to all exit blocks.
+/// Restores: walk idf from each MBB in restore set ensuring that
+/// all CSRs restored at MBB are spilled on all paths
+/// reaching MBB.
+///
+void PEI::verifySpillRestorePlacement() {
+ unsigned numReturnBlocks = 0;
+ for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ if (isReturnBlock(MBB) || MBB->succ_size() == 0)
+ ++numReturnBlocks;
+ }
+ for (CSRegBlockMap::iterator BI = CSRSave.begin(),
+ BE = CSRSave.end(); BI != BE; ++BI) {
+ MachineBasicBlock* MBB = BI->first;
+ CSRegSet spilled = BI->second;
+ CSRegSet restored;
+
+ if (spilled.empty())
+ continue;
+
+ DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(spilled)
+ << " RESTORE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
+
+ if (CSRRestore[MBB].intersects(spilled)) {
+ restored |= (CSRRestore[MBB] & spilled);
+ }
+
+ // Walk depth first from MBB to find restores of all CSRs spilled at MBB:
+ // we must find restores for all spills w/no intervening spills on all
+ // paths from MBB to all return blocks.
+ for (df_iterator<MachineBasicBlock*> BI = df_begin(MBB),
+ BE = df_end(MBB); BI != BE; ++BI) {
+ MachineBasicBlock* SBB = *BI;
+ if (SBB == MBB)
+ continue;
+ // Stop when we encounter spills of any CSRs spilled at MBB that
+ // have not yet been seen to be restored.
+ if (CSRSave[SBB].intersects(spilled) &&
+ !restored.contains(CSRSave[SBB] & spilled))
+ break;
+ // Collect the CSRs spilled at MBB that are restored
+ // at this DF successor of MBB.
+ if (CSRRestore[SBB].intersects(spilled))
+ restored |= (CSRRestore[SBB] & spilled);
+ // If we are at a retun block, check that the restores
+ // we have seen so far exhaust the spills at MBB, then
+ // reset the restores.
+ if (isReturnBlock(SBB) || SBB->succ_size() == 0) {
+ if (restored != spilled) {
+ CSRegSet notRestored = (spilled - restored);
+ DOUT << MF->getFunction()->getName() << ": "
+ << stringifyCSRegSet(notRestored)
+ << " spilled at " << getBasicBlockName(MBB)
+ << " are never restored on path to return "
+ << getBasicBlockName(SBB) << "\n";
+ }
+ restored.clear();
+ }
+ }
+ }
+
+ // Check restore placements.
+ for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
+ BE = CSRRestore.end(); BI != BE; ++BI) {
+ MachineBasicBlock* MBB = BI->first;
+ CSRegSet restored = BI->second;
+ CSRegSet spilled;
+
+ if (restored.empty())
+ continue;
+
+ DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRSave[MBB])
+ << " RESTORE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(restored) << "\n";
+
+ if (CSRSave[MBB].intersects(restored)) {
+ spilled |= (CSRSave[MBB] & restored);
+ }
+ // Walk inverse depth first from MBB to find spills of all
+ // CSRs restored at MBB:
+ for (idf_iterator<MachineBasicBlock*> BI = idf_begin(MBB),
+ BE = idf_end(MBB); BI != BE; ++BI) {
+ MachineBasicBlock* PBB = *BI;
+ if (PBB == MBB)
+ continue;
+ // Stop when we encounter restores of any CSRs restored at MBB that
+ // have not yet been seen to be spilled.
+ if (CSRRestore[PBB].intersects(restored) &&
+ !spilled.contains(CSRRestore[PBB] & restored))
+ break;
+ // Collect the CSRs restored at MBB that are spilled
+ // at this DF predecessor of MBB.
+ if (CSRSave[PBB].intersects(restored))
+ spilled |= (CSRSave[PBB] & restored);
+ }
+ if (spilled != restored) {
+ CSRegSet notSpilled = (restored - spilled);
+ DOUT << MF->getFunction()->getName() << ": "
+ << stringifyCSRegSet(notSpilled)
+ << " restored at " << getBasicBlockName(MBB)
+ << " are never spilled\n";
+ }
+ }
+}
+
+// Debugging print methods.
+std::string PEI::getBasicBlockName(const MachineBasicBlock* MBB) {
+ std::ostringstream name;
+ if (MBB) {
+ if (MBB->getBasicBlock())
+ name << MBB->getBasicBlock()->getName();
+ else
+ name << "_MBB_" << MBB->getNumber();
+ }
+ return name.str();
+}
+
+std::string PEI::stringifyCSRegSet(const CSRegSet& s) {
+ const TargetRegisterInfo* TRI = MF->getTarget().getRegisterInfo();
+ const std::vector<CalleeSavedInfo> CSI =
+ MF->getFrameInfo()->getCalleeSavedInfo();
+
+ std::ostringstream srep;
+ if (CSI.size() == 0) {
+ srep << "[]";
+ return srep.str();
+ }
+ srep << "[";
+ CSRegSet::iterator I = s.begin(), E = s.end();
+ if (I != E) {
+ unsigned reg = CSI[*I].getReg();
+ srep << TRI->getName(reg);
+ for (++I; I != E; ++I) {
+ reg = CSI[*I].getReg();
+ srep << ",";
+ srep << TRI->getName(reg);
+ }
+ }
+ srep << "]";
+ return srep.str();
+}
+
+void PEI::dumpSet(const CSRegSet& s) {
+ DOUT << stringifyCSRegSet(s) << "\n";
+}
+
+void PEI::dumpUsed(MachineBasicBlock* MBB) {
+ if (MBB) {
+ DOUT << "CSRUsed[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRUsed[MBB]) << "\n";
+ }
+}
+
+void PEI::dumpAllUsed() {
+ for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ dumpUsed(MBB);
+ }
+}
+
+void PEI::dumpSets(MachineBasicBlock* MBB) {
+ if (MBB) {
+ DOUT << getBasicBlockName(MBB) << " | "
+ << stringifyCSRegSet(CSRUsed[MBB]) << " | "
+ << stringifyCSRegSet(AnticIn[MBB]) << " | "
+ << stringifyCSRegSet(AnticOut[MBB]) << " | "
+ << stringifyCSRegSet(AvailIn[MBB]) << " | "
+ << stringifyCSRegSet(AvailOut[MBB]) << "\n";
+ }
+}
+
+void PEI::dumpSets1(MachineBasicBlock* MBB) {
+ if (MBB) {
+ DOUT << getBasicBlockName(MBB) << " | "
+ << stringifyCSRegSet(CSRUsed[MBB]) << " | "
+ << stringifyCSRegSet(AnticIn[MBB]) << " | "
+ << stringifyCSRegSet(AnticOut[MBB]) << " | "
+ << stringifyCSRegSet(AvailIn[MBB]) << " | "
+ << stringifyCSRegSet(AvailOut[MBB]) << " | "
+ << stringifyCSRegSet(CSRSave[MBB]) << " | "
+ << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
+ }
+}
+
+void PEI::dumpAllSets() {
+ for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
+ MBBI != MBBE; ++MBBI) {
+ MachineBasicBlock* MBB = MBBI;
+ dumpSets1(MBB);
+ }
+}
+
+void PEI::dumpSRSets() {
+ for (MachineFunction::iterator MBB = MF->begin(), E = MF->end();
+ MBB != E; ++MBB) {
+ if (! CSRSave[MBB].empty()) {
+ DOUT << "SAVE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRSave[MBB]);
+ if (CSRRestore[MBB].empty())
+ DOUT << "\n";
+ }
+ if (! CSRRestore[MBB].empty()) {
+ if (! CSRSave[MBB].empty())
+ DOUT << " ";
+ DOUT << "RESTORE[" << getBasicBlockName(MBB) << "] = "
+ << stringifyCSRegSet(CSRRestore[MBB]) << "\n";
+ }
+ }
+}
+#endif
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