[llvm] r296399 - [WebAssembly] Split CFG-sorting into its own pass. NFC.
Dan Gohman via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 27 14:38:58 PST 2017
Author: djg
Date: Mon Feb 27 16:38:58 2017
New Revision: 296399
URL: http://llvm.org/viewvc/llvm-project?rev=296399&view=rev
Log:
[WebAssembly] Split CFG-sorting into its own pass. NFC.
CFG sorting was already an independent algorithm from block/loop insertion;
this change makes it more convenient to debug.
Added:
llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp
- copied, changed from r296368, llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
Modified:
llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt
llvm/trunk/lib/Target/WebAssembly/WebAssembly.h
llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.h
Modified: llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt (original)
+++ llvm/trunk/lib/Target/WebAssembly/CMakeLists.txt Mon Feb 27 16:38:58 2017
@@ -14,6 +14,7 @@ add_llvm_target(WebAssemblyCodeGen
WebAssemblyAsmPrinter.cpp
WebAssemblyCallIndirectFixup.cpp
WebAssemblyCFGStackify.cpp
+ WebAssemblyCFGSort.cpp
WebAssemblyExplicitLocals.cpp
WebAssemblyFastISel.cpp
WebAssemblyFixIrreducibleControlFlow.cpp
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssembly.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssembly.h?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssembly.h (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssembly.h Mon Feb 27 16:38:58 2017
@@ -46,6 +46,7 @@ FunctionPass *createWebAssemblyRegStacki
FunctionPass *createWebAssemblyRegColoring();
FunctionPass *createWebAssemblyExplicitLocals();
FunctionPass *createWebAssemblyFixIrreducibleControlFlow();
+FunctionPass *createWebAssemblyCFGSort();
FunctionPass *createWebAssemblyCFGStackify();
FunctionPass *createWebAssemblyLowerBrUnless();
FunctionPass *createWebAssemblyRegNumbering();
Copied: llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp (from r296368, llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp)
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp?p2=llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp&p1=llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp&r1=296368&r2=296399&rev=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp Mon Feb 27 16:38:58 2017
@@ -1,4 +1,4 @@
-//===-- WebAssemblyCFGStackify.cpp - CFG Stackification -------------------===//
+//===-- WebAssemblyCFGSort.cpp - CFG Sorting ------------------------------===//
//
// The LLVM Compiler Infrastructure
//
@@ -8,31 +8,23 @@
//===----------------------------------------------------------------------===//
///
/// \file
-/// \brief This file implements a CFG stacking pass.
+/// \brief This file implements a CFG sorting pass.
///
/// This pass reorders the blocks in a function to put them into topological
/// order, ignoring loop backedges, and without any loop being interrupted
/// by a block not dominated by the loop header, with special care to keep the
/// order as similar as possible to the original order.
///
-/// Then, it inserts BLOCK and LOOP markers to mark the start of scopes, since
-/// scope boundaries serve as the labels for WebAssembly's control transfers.
-///
-/// This is sufficient to convert arbitrary CFGs into a form that works on
-/// WebAssembly, provided that all loops are single-entry.
-///
-//===----------------------------------------------------------------------===//
+////===----------------------------------------------------------------------===//
#include "WebAssembly.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
-#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyUtilities.h"
#include "llvm/ADT/PriorityQueue.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
-#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
@@ -40,11 +32,11 @@
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-#define DEBUG_TYPE "wasm-cfg-stackify"
+#define DEBUG_TYPE "wasm-cfg-sort"
namespace {
-class WebAssemblyCFGStackify final : public MachineFunctionPass {
- StringRef getPassName() const override { return "WebAssembly CFG Stackify"; }
+class WebAssemblyCFGSort final : public MachineFunctionPass {
+ StringRef getPassName() const override { return "WebAssembly CFG Sort"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
@@ -59,24 +51,13 @@ class WebAssemblyCFGStackify final : pub
public:
static char ID; // Pass identification, replacement for typeid
- WebAssemblyCFGStackify() : MachineFunctionPass(ID) {}
+ WebAssemblyCFGSort() : MachineFunctionPass(ID) {}
};
} // end anonymous namespace
-char WebAssemblyCFGStackify::ID = 0;
-FunctionPass *llvm::createWebAssemblyCFGStackify() {
- return new WebAssemblyCFGStackify();
-}
-
-/// Return the "bottom" block of a loop. This differs from
-/// MachineLoop::getBottomBlock in that it works even if the loop is
-/// discontiguous.
-static MachineBasicBlock *LoopBottom(const MachineLoop *Loop) {
- MachineBasicBlock *Bottom = Loop->getHeader();
- for (MachineBasicBlock *MBB : Loop->blocks())
- if (MBB->getNumber() > Bottom->getNumber())
- Bottom = MBB;
- return Bottom;
+char WebAssemblyCFGSort::ID = 0;
+FunctionPass *llvm::createWebAssemblyCFGSort() {
+ return new WebAssemblyCFGSort();
}
static void MaybeUpdateTerminator(MachineBasicBlock *MBB) {
@@ -124,7 +105,7 @@ struct Entry {
explicit Entry(const MachineLoop *L)
: Loop(L), NumBlocksLeft(L->getNumBlocks()) {}
};
-}
+} // end anonymous namespace
/// Sort the blocks, taking special care to make sure that loops are not
/// interrupted by blocks not dominated by their header.
@@ -279,315 +260,18 @@ static void SortBlocks(MachineFunction &
#endif
}
-/// Test whether Pred has any terminators explicitly branching to MBB, as
-/// opposed to falling through. Note that it's possible (eg. in unoptimized
-/// code) for a branch instruction to both branch to a block and fallthrough
-/// to it, so we check the actual branch operands to see if there are any
-/// explicit mentions.
-static bool ExplicitlyBranchesTo(MachineBasicBlock *Pred,
- MachineBasicBlock *MBB) {
- for (MachineInstr &MI : Pred->terminators())
- for (MachineOperand &MO : MI.explicit_operands())
- if (MO.isMBB() && MO.getMBB() == MBB)
- return true;
- return false;
-}
-
-/// Insert a BLOCK marker for branches to MBB (if needed).
-static void PlaceBlockMarker(
- MachineBasicBlock &MBB, MachineFunction &MF,
- SmallVectorImpl<MachineBasicBlock *> &ScopeTops,
- DenseMap<const MachineInstr *, MachineInstr *> &BlockTops,
- DenseMap<const MachineInstr *, MachineInstr *> &LoopTops,
- const WebAssemblyInstrInfo &TII,
- const MachineLoopInfo &MLI,
- MachineDominatorTree &MDT,
- WebAssemblyFunctionInfo &MFI) {
- // First compute the nearest common dominator of all forward non-fallthrough
- // predecessors so that we minimize the time that the BLOCK is on the stack,
- // which reduces overall stack height.
- MachineBasicBlock *Header = nullptr;
- bool IsBranchedTo = false;
- int MBBNumber = MBB.getNumber();
- for (MachineBasicBlock *Pred : MBB.predecessors())
- if (Pred->getNumber() < MBBNumber) {
- Header = Header ? MDT.findNearestCommonDominator(Header, Pred) : Pred;
- if (ExplicitlyBranchesTo(Pred, &MBB))
- IsBranchedTo = true;
- }
- if (!Header)
- return;
- if (!IsBranchedTo)
- return;
-
- assert(&MBB != &MF.front() && "Header blocks shouldn't have predecessors");
- MachineBasicBlock *LayoutPred = &*std::prev(MachineFunction::iterator(&MBB));
-
- // If the nearest common dominator is inside a more deeply nested context,
- // walk out to the nearest scope which isn't more deeply nested.
- for (MachineFunction::iterator I(LayoutPred), E(Header); I != E; --I) {
- if (MachineBasicBlock *ScopeTop = ScopeTops[I->getNumber()]) {
- if (ScopeTop->getNumber() > Header->getNumber()) {
- // Skip over an intervening scope.
- I = std::next(MachineFunction::iterator(ScopeTop));
- } else {
- // We found a scope level at an appropriate depth.
- Header = ScopeTop;
- break;
- }
- }
- }
-
- // Decide where in Header to put the BLOCK.
- MachineBasicBlock::iterator InsertPos;
- MachineLoop *HeaderLoop = MLI.getLoopFor(Header);
- if (HeaderLoop && MBB.getNumber() > LoopBottom(HeaderLoop)->getNumber()) {
- // Header is the header of a loop that does not lexically contain MBB, so
- // the BLOCK needs to be above the LOOP, after any END constructs.
- InsertPos = Header->begin();
- while (InsertPos->getOpcode() == WebAssembly::END_BLOCK ||
- InsertPos->getOpcode() == WebAssembly::END_LOOP)
- ++InsertPos;
- } else {
- // Otherwise, insert the BLOCK as late in Header as we can, but before the
- // beginning of the local expression tree and any nested BLOCKs.
- InsertPos = Header->getFirstTerminator();
- while (InsertPos != Header->begin() &&
- WebAssembly::isChild(*std::prev(InsertPos), MFI) &&
- std::prev(InsertPos)->getOpcode() != WebAssembly::LOOP &&
- std::prev(InsertPos)->getOpcode() != WebAssembly::END_BLOCK &&
- std::prev(InsertPos)->getOpcode() != WebAssembly::END_LOOP)
- --InsertPos;
- }
-
- // Add the BLOCK.
- MachineInstr *Begin = BuildMI(*Header, InsertPos, DebugLoc(),
- TII.get(WebAssembly::BLOCK))
- .addImm(int64_t(WebAssembly::ExprType::Void));
-
- // Mark the end of the block.
- InsertPos = MBB.begin();
- while (InsertPos != MBB.end() &&
- InsertPos->getOpcode() == WebAssembly::END_LOOP &&
- LoopTops[&*InsertPos]->getParent()->getNumber() >= Header->getNumber())
- ++InsertPos;
- MachineInstr *End = BuildMI(MBB, InsertPos, DebugLoc(),
- TII.get(WebAssembly::END_BLOCK));
- BlockTops[End] = Begin;
-
- // Track the farthest-spanning scope that ends at this point.
- int Number = MBB.getNumber();
- if (!ScopeTops[Number] ||
- ScopeTops[Number]->getNumber() > Header->getNumber())
- ScopeTops[Number] = Header;
-}
-
-/// Insert a LOOP marker for a loop starting at MBB (if it's a loop header).
-static void PlaceLoopMarker(
- MachineBasicBlock &MBB, MachineFunction &MF,
- SmallVectorImpl<MachineBasicBlock *> &ScopeTops,
- DenseMap<const MachineInstr *, MachineInstr *> &LoopTops,
- const WebAssemblyInstrInfo &TII, const MachineLoopInfo &MLI) {
- MachineLoop *Loop = MLI.getLoopFor(&MBB);
- if (!Loop || Loop->getHeader() != &MBB)
- return;
-
- // The operand of a LOOP is the first block after the loop. If the loop is the
- // bottom of the function, insert a dummy block at the end.
- MachineBasicBlock *Bottom = LoopBottom(Loop);
- auto Iter = std::next(MachineFunction::iterator(Bottom));
- if (Iter == MF.end()) {
- MachineBasicBlock *Label = MF.CreateMachineBasicBlock();
- // Give it a fake predecessor so that AsmPrinter prints its label.
- Label->addSuccessor(Label);
- MF.push_back(Label);
- Iter = std::next(MachineFunction::iterator(Bottom));
- }
- MachineBasicBlock *AfterLoop = &*Iter;
-
- // Mark the beginning of the loop (after the end of any existing loop that
- // ends here).
- auto InsertPos = MBB.begin();
- while (InsertPos != MBB.end() &&
- InsertPos->getOpcode() == WebAssembly::END_LOOP)
- ++InsertPos;
- MachineInstr *Begin = BuildMI(MBB, InsertPos, DebugLoc(),
- TII.get(WebAssembly::LOOP))
- .addImm(int64_t(WebAssembly::ExprType::Void));
-
- // Mark the end of the loop.
- MachineInstr *End = BuildMI(*AfterLoop, AfterLoop->begin(), DebugLoc(),
- TII.get(WebAssembly::END_LOOP));
- LoopTops[End] = Begin;
-
- assert((!ScopeTops[AfterLoop->getNumber()] ||
- ScopeTops[AfterLoop->getNumber()]->getNumber() < MBB.getNumber()) &&
- "With block sorting the outermost loop for a block should be first.");
- if (!ScopeTops[AfterLoop->getNumber()])
- ScopeTops[AfterLoop->getNumber()] = &MBB;
-}
-
-static unsigned
-GetDepth(const SmallVectorImpl<const MachineBasicBlock *> &Stack,
- const MachineBasicBlock *MBB) {
- unsigned Depth = 0;
- for (auto X : reverse(Stack)) {
- if (X == MBB)
- break;
- ++Depth;
- }
- assert(Depth < Stack.size() && "Branch destination should be in scope");
- return Depth;
-}
-
-/// In normal assembly languages, when the end of a function is unreachable,
-/// because the function ends in an infinite loop or a noreturn call or similar,
-/// it isn't necessary to worry about the function return type at the end of
-/// the function, because it's never reached. However, in WebAssembly, blocks
-/// that end at the function end need to have a return type signature that
-/// matches the function signature, even though it's unreachable. This function
-/// checks for such cases and fixes up the signatures.
-static void FixEndsAtEndOfFunction(
- MachineFunction &MF,
- const WebAssemblyFunctionInfo &MFI,
- DenseMap<const MachineInstr *, MachineInstr *> &BlockTops,
- DenseMap<const MachineInstr *, MachineInstr *> &LoopTops) {
- assert(MFI.getResults().size() <= 1);
-
- if (MFI.getResults().empty())
- return;
-
- WebAssembly::ExprType retType;
- switch (MFI.getResults().front().SimpleTy) {
- case MVT::i32: retType = WebAssembly::ExprType::I32; break;
- case MVT::i64: retType = WebAssembly::ExprType::I64; break;
- case MVT::f32: retType = WebAssembly::ExprType::F32; break;
- case MVT::f64: retType = WebAssembly::ExprType::F64; break;
- case MVT::v16i8: retType = WebAssembly::ExprType::I8x16; break;
- case MVT::v8i16: retType = WebAssembly::ExprType::I16x8; break;
- case MVT::v4i32: retType = WebAssembly::ExprType::I32x4; break;
- case MVT::v4f32: retType = WebAssembly::ExprType::F32x4; break;
- default: llvm_unreachable("unexpected return type");
- }
-
- for (MachineBasicBlock &MBB : reverse(MF)) {
- for (MachineInstr &MI : reverse(MBB)) {
- if (MI.isPosition() || MI.isDebugValue())
- continue;
- if (MI.getOpcode() == WebAssembly::END_BLOCK) {
- BlockTops[&MI]->getOperand(0).setImm(int32_t(retType));
- continue;
- }
- if (MI.getOpcode() == WebAssembly::END_LOOP) {
- LoopTops[&MI]->getOperand(0).setImm(int32_t(retType));
- continue;
- }
- // Something other than an `end`. We're done.
- return;
- }
- }
-}
-
-// WebAssembly functions end with an end instruction, as if the function body
-// were a block.
-static void AppendEndToFunction(
- MachineFunction &MF,
- const WebAssemblyInstrInfo &TII) {
- BuildMI(MF.back(), MF.back().end(), DebugLoc(),
- TII.get(WebAssembly::END_FUNCTION));
-}
-
-/// Insert LOOP and BLOCK markers at appropriate places.
-static void PlaceMarkers(MachineFunction &MF, const MachineLoopInfo &MLI,
- const WebAssemblyInstrInfo &TII,
- MachineDominatorTree &MDT,
- WebAssemblyFunctionInfo &MFI) {
- // For each block whose label represents the end of a scope, record the block
- // which holds the beginning of the scope. This will allow us to quickly skip
- // over scoped regions when walking blocks. We allocate one more than the
- // number of blocks in the function to accommodate for the possible fake block
- // we may insert at the end.
- SmallVector<MachineBasicBlock *, 8> ScopeTops(MF.getNumBlockIDs() + 1);
-
- // For each LOOP_END, the corresponding LOOP.
- DenseMap<const MachineInstr *, MachineInstr *> LoopTops;
-
- // For each END_BLOCK, the corresponding BLOCK.
- DenseMap<const MachineInstr *, MachineInstr *> BlockTops;
-
- for (auto &MBB : MF) {
- // Place the LOOP for MBB if MBB is the header of a loop.
- PlaceLoopMarker(MBB, MF, ScopeTops, LoopTops, TII, MLI);
-
- // Place the BLOCK for MBB if MBB is branched to from above.
- PlaceBlockMarker(MBB, MF, ScopeTops, BlockTops, LoopTops, TII, MLI, MDT, MFI);
- }
-
- // Now rewrite references to basic blocks to be depth immediates.
- SmallVector<const MachineBasicBlock *, 8> Stack;
- for (auto &MBB : reverse(MF)) {
- for (auto &MI : reverse(MBB)) {
- switch (MI.getOpcode()) {
- case WebAssembly::BLOCK:
- assert(ScopeTops[Stack.back()->getNumber()]->getNumber() <= MBB.getNumber() &&
- "Block should be balanced");
- Stack.pop_back();
- break;
- case WebAssembly::LOOP:
- assert(Stack.back() == &MBB && "Loop top should be balanced");
- Stack.pop_back();
- break;
- case WebAssembly::END_BLOCK:
- Stack.push_back(&MBB);
- break;
- case WebAssembly::END_LOOP:
- Stack.push_back(LoopTops[&MI]->getParent());
- break;
- default:
- if (MI.isTerminator()) {
- // Rewrite MBB operands to be depth immediates.
- SmallVector<MachineOperand, 4> Ops(MI.operands());
- while (MI.getNumOperands() > 0)
- MI.RemoveOperand(MI.getNumOperands() - 1);
- for (auto MO : Ops) {
- if (MO.isMBB())
- MO = MachineOperand::CreateImm(GetDepth(Stack, MO.getMBB()));
- MI.addOperand(MF, MO);
- }
- }
- break;
- }
- }
- }
- assert(Stack.empty() && "Control flow should be balanced");
-
- // Fix up block/loop signatures at the end of the function to conform to
- // WebAssembly's rules.
- FixEndsAtEndOfFunction(MF, MFI, BlockTops, LoopTops);
-
- // Add an end instruction at the end of the function body.
- if (!MF.getSubtarget<WebAssemblySubtarget>()
- .getTargetTriple().isOSBinFormatELF())
- AppendEndToFunction(MF, TII);
-}
-
-bool WebAssemblyCFGStackify::runOnMachineFunction(MachineFunction &MF) {
- DEBUG(dbgs() << "********** CFG Stackifying **********\n"
+bool WebAssemblyCFGSort::runOnMachineFunction(MachineFunction &MF) {
+ DEBUG(dbgs() << "********** CFG Sorting **********\n"
"********** Function: "
<< MF.getName() << '\n');
const auto &MLI = getAnalysis<MachineLoopInfo>();
auto &MDT = getAnalysis<MachineDominatorTree>();
// Liveness is not tracked for VALUE_STACK physreg.
- const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
- WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
MF.getRegInfo().invalidateLiveness();
// Sort the blocks, with contiguous loops.
SortBlocks(MF, MLI, MDT);
- // Place the BLOCK and LOOP markers to indicate the beginnings of scopes.
- PlaceMarkers(MF, MLI, TII, MDT, MFI);
-
return true;
}
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp Mon Feb 27 16:38:58 2017
@@ -10,12 +10,7 @@
/// \file
/// \brief This file implements a CFG stacking pass.
///
-/// This pass reorders the blocks in a function to put them into topological
-/// order, ignoring loop backedges, and without any loop being interrupted
-/// by a block not dominated by the loop header, with special care to keep the
-/// order as similar as possible to the original order.
-///
-/// Then, it inserts BLOCK and LOOP markers to mark the start of scopes, since
+/// This pass inserts BLOCK and LOOP markers to mark the start of scopes, since
/// scope boundaries serve as the labels for WebAssembly's control transfers.
///
/// This is sufficient to convert arbitrary CFGs into a form that works on
@@ -28,8 +23,6 @@
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyUtilities.h"
-#include "llvm/ADT/PriorityQueue.h"
-#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -68,217 +61,6 @@ FunctionPass *llvm::createWebAssemblyCFG
return new WebAssemblyCFGStackify();
}
-/// Return the "bottom" block of a loop. This differs from
-/// MachineLoop::getBottomBlock in that it works even if the loop is
-/// discontiguous.
-static MachineBasicBlock *LoopBottom(const MachineLoop *Loop) {
- MachineBasicBlock *Bottom = Loop->getHeader();
- for (MachineBasicBlock *MBB : Loop->blocks())
- if (MBB->getNumber() > Bottom->getNumber())
- Bottom = MBB;
- return Bottom;
-}
-
-static void MaybeUpdateTerminator(MachineBasicBlock *MBB) {
-#ifndef NDEBUG
- bool AnyBarrier = false;
-#endif
- bool AllAnalyzable = true;
- for (const MachineInstr &Term : MBB->terminators()) {
-#ifndef NDEBUG
- AnyBarrier |= Term.isBarrier();
-#endif
- AllAnalyzable &= Term.isBranch() && !Term.isIndirectBranch();
- }
- assert((AnyBarrier || AllAnalyzable) &&
- "AnalyzeBranch needs to analyze any block with a fallthrough");
- if (AllAnalyzable)
- MBB->updateTerminator();
-}
-
-namespace {
-/// Sort blocks by their number.
-struct CompareBlockNumbers {
- bool operator()(const MachineBasicBlock *A,
- const MachineBasicBlock *B) const {
- return A->getNumber() > B->getNumber();
- }
-};
-/// Sort blocks by their number in the opposite order..
-struct CompareBlockNumbersBackwards {
- bool operator()(const MachineBasicBlock *A,
- const MachineBasicBlock *B) const {
- return A->getNumber() < B->getNumber();
- }
-};
-/// Bookkeeping for a loop to help ensure that we don't mix blocks not dominated
-/// by the loop header among the loop's blocks.
-struct Entry {
- const MachineLoop *Loop;
- unsigned NumBlocksLeft;
-
- /// List of blocks not dominated by Loop's header that are deferred until
- /// after all of Loop's blocks have been seen.
- std::vector<MachineBasicBlock *> Deferred;
-
- explicit Entry(const MachineLoop *L)
- : Loop(L), NumBlocksLeft(L->getNumBlocks()) {}
-};
-}
-
-/// Sort the blocks, taking special care to make sure that loops are not
-/// interrupted by blocks not dominated by their header.
-/// TODO: There are many opportunities for improving the heuristics here.
-/// Explore them.
-static void SortBlocks(MachineFunction &MF, const MachineLoopInfo &MLI,
- const MachineDominatorTree &MDT) {
- // Prepare for a topological sort: Record the number of predecessors each
- // block has, ignoring loop backedges.
- MF.RenumberBlocks();
- SmallVector<unsigned, 16> NumPredsLeft(MF.getNumBlockIDs(), 0);
- for (MachineBasicBlock &MBB : MF) {
- unsigned N = MBB.pred_size();
- if (MachineLoop *L = MLI.getLoopFor(&MBB))
- if (L->getHeader() == &MBB)
- for (const MachineBasicBlock *Pred : MBB.predecessors())
- if (L->contains(Pred))
- --N;
- NumPredsLeft[MBB.getNumber()] = N;
- }
-
- // Topological sort the CFG, with additional constraints:
- // - Between a loop header and the last block in the loop, there can be
- // no blocks not dominated by the loop header.
- // - It's desirable to preserve the original block order when possible.
- // We use two ready lists; Preferred and Ready. Preferred has recently
- // processed sucessors, to help preserve block sequences from the original
- // order. Ready has the remaining ready blocks.
- PriorityQueue<MachineBasicBlock *, std::vector<MachineBasicBlock *>,
- CompareBlockNumbers>
- Preferred;
- PriorityQueue<MachineBasicBlock *, std::vector<MachineBasicBlock *>,
- CompareBlockNumbersBackwards>
- Ready;
- SmallVector<Entry, 4> Loops;
- for (MachineBasicBlock *MBB = &MF.front();;) {
- const MachineLoop *L = MLI.getLoopFor(MBB);
- if (L) {
- // If MBB is a loop header, add it to the active loop list. We can't put
- // any blocks that it doesn't dominate until we see the end of the loop.
- if (L->getHeader() == MBB)
- Loops.push_back(Entry(L));
- // For each active loop the block is in, decrement the count. If MBB is
- // the last block in an active loop, take it off the list and pick up any
- // blocks deferred because the header didn't dominate them.
- for (Entry &E : Loops)
- if (E.Loop->contains(MBB) && --E.NumBlocksLeft == 0)
- for (auto DeferredBlock : E.Deferred)
- Ready.push(DeferredBlock);
- while (!Loops.empty() && Loops.back().NumBlocksLeft == 0)
- Loops.pop_back();
- }
- // The main topological sort logic.
- for (MachineBasicBlock *Succ : MBB->successors()) {
- // Ignore backedges.
- if (MachineLoop *SuccL = MLI.getLoopFor(Succ))
- if (SuccL->getHeader() == Succ && SuccL->contains(MBB))
- continue;
- // Decrement the predecessor count. If it's now zero, it's ready.
- if (--NumPredsLeft[Succ->getNumber()] == 0)
- Preferred.push(Succ);
- }
- // Determine the block to follow MBB. First try to find a preferred block,
- // to preserve the original block order when possible.
- MachineBasicBlock *Next = nullptr;
- while (!Preferred.empty()) {
- Next = Preferred.top();
- Preferred.pop();
- // If X isn't dominated by the top active loop header, defer it until that
- // loop is done.
- if (!Loops.empty() &&
- !MDT.dominates(Loops.back().Loop->getHeader(), Next)) {
- Loops.back().Deferred.push_back(Next);
- Next = nullptr;
- continue;
- }
- // If Next was originally ordered before MBB, and it isn't because it was
- // loop-rotated above the header, it's not preferred.
- if (Next->getNumber() < MBB->getNumber() &&
- (!L || !L->contains(Next) ||
- L->getHeader()->getNumber() < Next->getNumber())) {
- Ready.push(Next);
- Next = nullptr;
- continue;
- }
- break;
- }
- // If we didn't find a suitable block in the Preferred list, check the
- // general Ready list.
- if (!Next) {
- // If there are no more blocks to process, we're done.
- if (Ready.empty()) {
- MaybeUpdateTerminator(MBB);
- break;
- }
- for (;;) {
- Next = Ready.top();
- Ready.pop();
- // If Next isn't dominated by the top active loop header, defer it until
- // that loop is done.
- if (!Loops.empty() &&
- !MDT.dominates(Loops.back().Loop->getHeader(), Next)) {
- Loops.back().Deferred.push_back(Next);
- continue;
- }
- break;
- }
- }
- // Move the next block into place and iterate.
- Next->moveAfter(MBB);
- MaybeUpdateTerminator(MBB);
- MBB = Next;
- }
- assert(Loops.empty() && "Active loop list not finished");
- MF.RenumberBlocks();
-
-#ifndef NDEBUG
- SmallSetVector<MachineLoop *, 8> OnStack;
-
- // Insert a sentinel representing the degenerate loop that starts at the
- // function entry block and includes the entire function as a "loop" that
- // executes once.
- OnStack.insert(nullptr);
-
- for (auto &MBB : MF) {
- assert(MBB.getNumber() >= 0 && "Renumbered blocks should be non-negative.");
-
- MachineLoop *Loop = MLI.getLoopFor(&MBB);
- if (Loop && &MBB == Loop->getHeader()) {
- // Loop header. The loop predecessor should be sorted above, and the other
- // predecessors should be backedges below.
- for (auto Pred : MBB.predecessors())
- assert(
- (Pred->getNumber() < MBB.getNumber() || Loop->contains(Pred)) &&
- "Loop header predecessors must be loop predecessors or backedges");
- assert(OnStack.insert(Loop) && "Loops should be declared at most once.");
- } else {
- // Not a loop header. All predecessors should be sorted above.
- for (auto Pred : MBB.predecessors())
- assert(Pred->getNumber() < MBB.getNumber() &&
- "Non-loop-header predecessors should be topologically sorted");
- assert(OnStack.count(MLI.getLoopFor(&MBB)) &&
- "Blocks must be nested in their loops");
- }
- while (OnStack.size() > 1 && &MBB == LoopBottom(OnStack.back()))
- OnStack.pop_back();
- }
- assert(OnStack.pop_back_val() == nullptr &&
- "The function entry block shouldn't actually be a loop header");
- assert(OnStack.empty() &&
- "Control flow stack pushes and pops should be balanced.");
-#endif
-}
-
/// Test whether Pred has any terminators explicitly branching to MBB, as
/// opposed to falling through. Note that it's possible (eg. in unoptimized
/// code) for a branch instruction to both branch to a block and fallthrough
@@ -583,9 +365,6 @@ bool WebAssemblyCFGStackify::runOnMachin
WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
MF.getRegInfo().invalidateLiveness();
- // Sort the blocks, with contiguous loops.
- SortBlocks(MF, MLI, MDT);
-
// Place the BLOCK and LOOP markers to indicate the beginnings of scopes.
PlaceMarkers(MF, MLI, TII, MDT, MFI);
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp Mon Feb 27 16:38:58 2017
@@ -280,7 +280,11 @@ void WebAssemblyPassConfig::addPreEmitPa
// Insert explicit get_local and set_local operators.
addPass(createWebAssemblyExplicitLocals());
- // Put the CFG in structured form; insert BLOCK and LOOP markers.
+ // Sort the blocks of the CFG into topological order, a prerequisite for
+ // BLOCK and LOOP markers.
+ addPass(createWebAssemblyCFGSort());
+
+ // Insert BLOCK and LOOP markers.
addPass(createWebAssemblyCFGStackify());
// Lower br_unless into br_if.
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.cpp?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.cpp Mon Feb 27 16:38:58 2017
@@ -15,6 +15,7 @@
#include "WebAssemblyUtilities.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
using namespace llvm;
bool WebAssembly::isArgument(const MachineInstr &MI) {
@@ -86,3 +87,11 @@ bool WebAssembly::isCallIndirect(const M
return false;
}
}
+
+MachineBasicBlock *llvm::LoopBottom(const MachineLoop *Loop) {
+ MachineBasicBlock *Bottom = Loop->getHeader();
+ for (MachineBasicBlock *MBB : Loop->blocks())
+ if (MBB->getNumber() > Bottom->getNumber())
+ Bottom = MBB;
+ return Bottom;
+}
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.h?rev=296399&r1=296398&r2=296399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.h (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyUtilities.h Mon Feb 27 16:38:58 2017
@@ -18,7 +18,9 @@
namespace llvm {
+class MachineBasicBlock;
class MachineInstr;
+class MachineLoop;
class WebAssemblyFunctionInfo;
namespace WebAssembly {
@@ -30,6 +32,12 @@ bool isChild(const MachineInstr &MI, con
bool isCallIndirect(const MachineInstr &MI);
} // end namespace WebAssembly
+
+/// Return the "bottom" block of a loop. This differs from
+/// MachineLoop::getBottomBlock in that it works even if the loop is
+/// discontiguous.
+MachineBasicBlock *LoopBottom(const MachineLoop *Loop);
+
} // end namespace llvm
#endif
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