[llvm-commits] [llvm] r106555 - in /llvm/trunk: include/llvm/CodeGen/MachineBasicBlock.h include/llvm/CodeGen/MachineLoopInfo.h lib/CodeGen/MachineBasicBlock.cpp lib/CodeGen/MachineLICM.cpp lib/CodeGen/PHIElimination.cpp
Dan Gohman
gohman at apple.com
Tue Jun 22 10:25:57 PDT 2010
Author: djg
Date: Tue Jun 22 12:25:57 2010
New Revision: 106555
URL: http://llvm.org/viewvc/llvm-project?rev=106555&view=rev
Log:
Move PHIElimination's SplitCriticalEdge for MachineBasicBlocks out
into a utility routine, teach it how to update MachineLoopInfo, and
make use of it in MachineLICM to split critical edges on demand.
Modified:
llvm/trunk/include/llvm/CodeGen/MachineBasicBlock.h
llvm/trunk/include/llvm/CodeGen/MachineLoopInfo.h
llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
llvm/trunk/lib/CodeGen/MachineLICM.cpp
llvm/trunk/lib/CodeGen/PHIElimination.cpp
Modified: llvm/trunk/include/llvm/CodeGen/MachineBasicBlock.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineBasicBlock.h?rev=106555&r1=106554&r2=106555&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineBasicBlock.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineBasicBlock.h Tue Jun 22 12:25:57 2010
@@ -19,6 +19,7 @@
namespace llvm {
+class Pass;
class BasicBlock;
class MachineFunction;
class MCSymbol;
@@ -281,6 +282,14 @@
/// it returns end()
iterator getFirstTerminator();
+ /// SplitCriticalEdge - Split the critical edge from this block to the
+ /// given successor block, and return the newly created block, or null
+ /// if splitting is not possible.
+ ///
+ /// This function updates LiveVariables, MachineDominatorTree, and
+ /// MachineLoopInfo, as applicable.
+ MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P);
+
void pop_front() { Insts.pop_front(); }
void pop_back() { Insts.pop_back(); }
void push_back(MachineInstr *MI) { Insts.push_back(MI); }
Modified: llvm/trunk/include/llvm/CodeGen/MachineLoopInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineLoopInfo.h?rev=106555&r1=106554&r2=106555&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineLoopInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineLoopInfo.h Tue Jun 22 12:25:57 2010
@@ -64,13 +64,13 @@
void operator=(const MachineLoopInfo &); // do not implement
MachineLoopInfo(const MachineLoopInfo &); // do not implement
- LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
-
public:
static char ID; // Pass identification, replacement for typeid
MachineLoopInfo() : MachineFunctionPass(&ID) {}
+ LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
+
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
Modified: llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp?rev=106555&r1=106554&r2=106555&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp Tue Jun 22 12:25:57 2010
@@ -13,7 +13,10 @@
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/BasicBlock.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/Target/TargetRegisterInfo.h"
@@ -396,6 +399,82 @@
return FBB == 0;
}
+MachineBasicBlock *
+MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
+ MachineFunction *MF = getParent();
+ DebugLoc dl; // FIXME: this is nowhere
+
+ // We may need to update this's terminator, but we can't do that if AnalyzeBranch
+ // fails. If this uses a jump table, we won't touch it.
+ const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
+ MachineBasicBlock *TBB = 0, *FBB = 0;
+ SmallVector<MachineOperand, 4> Cond;
+ if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
+ return NULL;
+
+ MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
+ MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
+ DEBUG(dbgs() << "PHIElimination splitting critical edge:"
+ " BB#" << getNumber()
+ << " -- BB#" << NMBB->getNumber()
+ << " -- BB#" << Succ->getNumber() << '\n');
+
+ ReplaceUsesOfBlockWith(Succ, NMBB);
+ updateTerminator();
+
+ // Insert unconditional "jump Succ" instruction in NMBB if necessary.
+ NMBB->addSuccessor(Succ);
+ if (!NMBB->isLayoutSuccessor(Succ)) {
+ Cond.clear();
+ MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
+ }
+
+ // Fix PHI nodes in Succ so they refer to NMBB instead of this
+ for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end();
+ i != e && i->isPHI(); ++i)
+ for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
+ if (i->getOperand(ni+1).getMBB() == this)
+ i->getOperand(ni+1).setMBB(NMBB);
+
+ if (LiveVariables *LV =
+ P->getAnalysisIfAvailable<LiveVariables>())
+ LV->addNewBlock(NMBB, this, Succ);
+
+ if (MachineDominatorTree *MDT =
+ P->getAnalysisIfAvailable<MachineDominatorTree>())
+ MDT->addNewBlock(NMBB, this);
+
+ if (MachineLoopInfo *MLI =
+ P->getAnalysisIfAvailable<MachineLoopInfo>())
+ if (MachineLoop *TIL = MLI->getLoopFor(this)) {
+ // If one or the other blocks were not in a loop, the new block is not
+ // either, and thus LI doesn't need to be updated.
+ if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
+ if (TIL == DestLoop) {
+ // Both in the same loop, the NMBB joins loop.
+ DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
+ } else if (TIL->contains(DestLoop)) {
+ // Edge from an outer loop to an inner loop. Add to the outer loop.
+ TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
+ } else if (DestLoop->contains(TIL)) {
+ // Edge from an inner loop to an outer loop. Add to the outer loop.
+ DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
+ } else {
+ // Edge from two loops with no containment relation. Because these
+ // are natural loops, we know that the destination block must be the
+ // header of its loop (adding a branch into a loop elsewhere would
+ // create an irreducible loop).
+ assert(DestLoop->getHeader() == Succ &&
+ "Should not create irreducible loops!");
+ if (MachineLoop *P = DestLoop->getParentLoop())
+ P->addBasicBlockToLoop(NMBB, MLI->getBase());
+ }
+ }
+ }
+
+ return NMBB;
+}
+
/// removeFromParent - This method unlinks 'this' from the containing function,
/// and returns it, but does not delete it.
MachineBasicBlock *MachineBasicBlock::removeFromParent() {
Modified: llvm/trunk/lib/CodeGen/MachineLICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineLICM.cpp?rev=106555&r1=106554&r2=106555&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineLICM.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineLICM.cpp Tue Jun 22 12:25:57 2010
@@ -83,7 +83,6 @@
const char *getPassName() const { return "Machine Instruction LICM"; }
- // FIXME: Loop preheaders?
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<MachineLoopInfo>();
@@ -182,6 +181,10 @@
/// current loop preheader that may become duplicates of instructions that
/// are hoisted out of the loop.
void InitCSEMap(MachineBasicBlock *BB);
+
+ /// getCurPreheader - Get the preheader for the current loop, splitting
+ /// a critical edge if needed.
+ MachineBasicBlock *getCurPreheader();
};
} // end anonymous namespace
@@ -193,11 +196,11 @@
return new MachineLICM(PreRegAlloc);
}
-/// LoopIsOuterMostWithPreheader - Test if the given loop is the outer-most
-/// loop that has a preheader.
-static bool LoopIsOuterMostWithPreheader(MachineLoop *CurLoop) {
+/// LoopIsOuterMostWithPredecessor - Test if the given loop is the outer-most
+/// loop that has a unique predecessor.
+static bool LoopIsOuterMostWithPredecessor(MachineLoop *CurLoop) {
for (MachineLoop *L = CurLoop->getParentLoop(); L; L = L->getParentLoop())
- if (L->getLoopPreheader())
+ if (L->getLoopPredecessor())
return false;
return true;
}
@@ -223,20 +226,11 @@
for (MachineLoopInfo::iterator I = MLI->begin(), E = MLI->end(); I != E; ++I){
CurLoop = *I;
+ CurPreheader = 0;
// If this is done before regalloc, only visit outer-most preheader-sporting
// loops.
- if (PreRegAlloc && !LoopIsOuterMostWithPreheader(CurLoop))
- continue;
-
- // Determine the block to which to hoist instructions. If we can't find a
- // suitable loop preheader, we can't do any hoisting.
- //
- // FIXME: We are only hoisting if the basic block coming into this loop
- // has only one successor. This isn't the case in general because we haven't
- // broken critical edges or added preheaders.
- CurPreheader = CurLoop->getLoopPreheader();
- if (!CurPreheader)
+ if (PreRegAlloc && !LoopIsOuterMostWithPredecessor(CurLoop))
continue;
if (!PreRegAlloc)
@@ -438,13 +432,16 @@
/// operands that is safe to hoist, this instruction is called to do the
/// dirty work.
void MachineLICM::HoistPostRA(MachineInstr *MI, unsigned Def) {
+ MachineBasicBlock *Preheader = getCurPreheader();
+ if (!Preheader) return;
+
// Now move the instructions to the predecessor, inserting it before any
// terminator instructions.
DEBUG({
dbgs() << "Hoisting " << *MI;
- if (CurPreheader->getBasicBlock())
+ if (Preheader->getBasicBlock())
dbgs() << " to MachineBasicBlock "
- << CurPreheader->getName();
+ << Preheader->getName();
if (MI->getParent()->getBasicBlock())
dbgs() << " from MachineBasicBlock "
<< MI->getParent()->getName();
@@ -453,7 +450,7 @@
// Splice the instruction to the preheader.
MachineBasicBlock *MBB = MI->getParent();
- CurPreheader->splice(CurPreheader->getFirstTerminator(), MBB, MI);
+ Preheader->splice(Preheader->getFirstTerminator(), MBB, MI);
// Add register to livein list to all the BBs in the current loop since a
// loop invariant must be kept live throughout the whole loop. This is
@@ -756,6 +753,9 @@
/// that are safe to hoist, this instruction is called to do the dirty work.
///
void MachineLICM::Hoist(MachineInstr *MI) {
+ MachineBasicBlock *Preheader = getCurPreheader();
+ if (!Preheader) return;
+
// First check whether we should hoist this instruction.
if (!IsLoopInvariantInst(*MI) || !IsProfitableToHoist(*MI)) {
// If not, try unfolding a hoistable load.
@@ -767,9 +767,9 @@
// terminator instructions.
DEBUG({
dbgs() << "Hoisting " << *MI;
- if (CurPreheader->getBasicBlock())
+ if (Preheader->getBasicBlock())
dbgs() << " to MachineBasicBlock "
- << CurPreheader->getName();
+ << Preheader->getName();
if (MI->getParent()->getBasicBlock())
dbgs() << " from MachineBasicBlock "
<< MI->getParent()->getName();
@@ -779,7 +779,7 @@
// If this is the first instruction being hoisted to the preheader,
// initialize the CSE map with potential common expressions.
if (FirstInLoop) {
- InitCSEMap(CurPreheader);
+ InitCSEMap(Preheader);
FirstInLoop = false;
}
@@ -789,7 +789,7 @@
CI = CSEMap.find(Opcode);
if (!EliminateCSE(MI, CI)) {
// Otherwise, splice the instruction to the preheader.
- CurPreheader->splice(CurPreheader->getFirstTerminator(),MI->getParent(),MI);
+ Preheader->splice(Preheader->getFirstTerminator(),MI->getParent(),MI);
// Clear the kill flags of any register this instruction defines,
// since they may need to be live throughout the entire loop
@@ -813,3 +813,30 @@
++NumHoisted;
Changed = true;
}
+
+MachineBasicBlock *MachineLICM::getCurPreheader() {
+ // Determine the block to which to hoist instructions. If we can't find a
+ // suitable loop predecessor, we can't do any hoisting.
+
+ // If we've tried to get a preheader and failed, don't try again.
+ if (CurPreheader == reinterpret_cast<MachineBasicBlock *>(-1))
+ return 0;
+
+ if (!CurPreheader) {
+ CurPreheader = CurLoop->getLoopPreheader();
+ if (!CurPreheader) {
+ MachineBasicBlock *Pred = CurLoop->getLoopPredecessor();
+ if (!Pred) {
+ CurPreheader = reinterpret_cast<MachineBasicBlock *>(-1);
+ return 0;
+ }
+
+ CurPreheader = Pred->SplitCriticalEdge(CurLoop->getHeader(), this);
+ if (!CurPreheader) {
+ CurPreheader = reinterpret_cast<MachineBasicBlock *>(-1);
+ return 0;
+ }
+ }
+ }
+ return CurPreheader;
+}
Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=106555&r1=106554&r2=106555&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Tue Jun 22 12:25:57 2010
@@ -34,7 +34,6 @@
using namespace llvm;
STATISTIC(NumAtomic, "Number of atomic phis lowered");
-STATISTIC(NumSplits, "Number of critical edges split on demand");
STATISTIC(NumReused, "Number of reused lowered phis");
char PHIElimination::ID = 0;
@@ -391,58 +390,8 @@
// (not considering PHI nodes). If the register is live in to this block
// anyway, we would gain nothing from splitting.
if (!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB))
- SplitCriticalEdge(PreMBB, &MBB);
+ PreMBB->SplitCriticalEdge(&MBB, this);
}
}
return true;
}
-
-MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
- MachineBasicBlock *B) {
- assert(A && B && "Missing MBB end point");
-
- MachineFunction *MF = A->getParent();
- DebugLoc dl; // FIXME: this is nowhere
-
- // We may need to update A's terminator, but we can't do that if AnalyzeBranch
- // fails. If A uses a jump table, we won't touch it.
- const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
- MachineBasicBlock *TBB = 0, *FBB = 0;
- SmallVector<MachineOperand, 4> Cond;
- if (TII->AnalyzeBranch(*A, TBB, FBB, Cond))
- return NULL;
-
- ++NumSplits;
-
- MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
- MF->insert(llvm::next(MachineFunction::iterator(A)), NMBB);
- DEBUG(dbgs() << "PHIElimination splitting critical edge:"
- " BB#" << A->getNumber()
- << " -- BB#" << NMBB->getNumber()
- << " -- BB#" << B->getNumber() << '\n');
-
- A->ReplaceUsesOfBlockWith(B, NMBB);
- A->updateTerminator();
-
- // Insert unconditional "jump B" instruction in NMBB if necessary.
- NMBB->addSuccessor(B);
- if (!NMBB->isLayoutSuccessor(B)) {
- Cond.clear();
- MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond, dl);
- }
-
- // Fix PHI nodes in B so they refer to NMBB instead of A
- for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
- i != e && i->isPHI(); ++i)
- for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
- if (i->getOperand(ni+1).getMBB() == A)
- i->getOperand(ni+1).setMBB(NMBB);
-
- if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
- LV->addNewBlock(NMBB, A, B);
-
- if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
- MDT->addNewBlock(NMBB, A);
-
- return NMBB;
-}
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