This is a fix for PR# 19051. I noticed code gen differences due to code motion when...
[oota-llvm.git] / lib / CodeGen / BranchFolding.cpp
index d349e0249b8f2ebd8b597fcf8ad4784b0a910eb3..bf6d56ceac8828c6cb69fffc16301e57ed377179 100644 (file)
@@ -27,7 +27,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
-#include "llvm/Function.h"
+#include "llvm/IR/Function.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -66,9 +66,9 @@ namespace {
     static char ID;
     explicit BranchFolderPass(): MachineFunctionPass(ID) {}
 
-    virtual bool runOnMachineFunction(MachineFunction &MF);
+    bool runOnMachineFunction(MachineFunction &MF) override;
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.addRequired<TargetPassConfig>();
       MachineFunctionPass::getAnalysisUsage(AU);
     }
@@ -83,7 +83,11 @@ INITIALIZE_PASS(BranchFolderPass, "branch-folder",
 
 bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
   TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
-  BranchFolder Folder(PassConfig->getEnableTailMerge(), /*CommonHoist=*/true);
+  // TailMerge can create jump into if branches that make CFG irreducible for
+  // HW that requires structurized CFG.
+  bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
+      PassConfig->getEnableTailMerge();
+  BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true);
   return Folder.OptimizeFunction(MF,
                                  MF.getTarget().getInstrInfo(),
                                  MF.getTarget().getRegisterInfo(),
@@ -135,8 +139,8 @@ bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) {
     if (!I->isImplicitDef())
       break;
     unsigned Reg = I->getOperand(0).getReg();
-    ImpDefRegs.insert(Reg);
-    for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+    for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+         SubRegs.isValid(); ++SubRegs)
       ImpDefRegs.insert(*SubRegs);
     ++I;
   }
@@ -379,7 +383,7 @@ void BranchFolder::MaintainLiveIns(MachineBasicBlock *CurMBB,
   if (RS) {
     RS->enterBasicBlock(CurMBB);
     if (!CurMBB->empty())
-      RS->forward(prior(CurMBB->end()));
+      RS->forward(std::prev(CurMBB->end()));
     BitVector RegsLiveAtExit(TRI->getNumRegs());
     RS->getRegsUsed(RegsLiveAtExit, false);
     for (unsigned int i = 0, e = TRI->getNumRegs(); i != e; i++)
@@ -406,7 +410,8 @@ void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
 /// MBB so that the part before the iterator falls into the part starting at the
 /// iterator.  This returns the new MBB.
 MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
-                                            MachineBasicBlock::iterator BBI1) {
+                                            MachineBasicBlock::iterator BBI1,
+                                            const BasicBlock *BB) {
   if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1))
     return 0;
 
@@ -414,7 +419,7 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
 
   // Create the fall-through block.
   MachineFunction::iterator MBBI = &CurMBB;
-  MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(CurMBB.getBasicBlock());
+  MachineBasicBlock *NewMBB =MF.CreateMachineBasicBlock(BB);
   CurMBB.getParent()->insert(++MBBI, NewMBB);
 
   // Move all the successors of this block to the specified block.
@@ -457,7 +462,7 @@ static unsigned EstimateRuntime(MachineBasicBlock::iterator I,
 static void FixTail(MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB,
                     const TargetInstrInfo *TII) {
   MachineFunction *MF = CurMBB->getParent();
-  MachineFunction::iterator I = llvm::next(MachineFunction::iterator(CurMBB));
+  MachineFunction::iterator I = std::next(MachineFunction::iterator(CurMBB));
   MachineBasicBlock *TBB = 0, *FBB = 0;
   SmallVector<MachineOperand, 4> Cond;
   DebugLoc dl;  // FIXME: this is nowhere
@@ -570,8 +575,8 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1,
   // instructions that would be deleted in the merge.
   MachineFunction *MF = MBB1->getParent();
   if (EffectiveTailLen >= 2 &&
-      MF->getFunction()->getFnAttributes().
-        hasAttribute(Attribute::OptimizeForSize) &&
+      MF->getFunction()->getAttributes().
+        hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize) &&
       (I1 == MBB1->begin() || I2 == MBB2->begin()))
     return true;
 
@@ -595,12 +600,11 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
   unsigned maxCommonTailLength = 0U;
   SameTails.clear();
   MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
-  MPIterator HighestMPIter = prior(MergePotentials.end());
-  for (MPIterator CurMPIter = prior(MergePotentials.end()),
+  MPIterator HighestMPIter = std::prev(MergePotentials.end());
+  for (MPIterator CurMPIter = std::prev(MergePotentials.end()),
                   B = MergePotentials.begin();
-       CurMPIter != B && CurMPIter->getHash() == CurHash;
-       --CurMPIter) {
-    for (MPIterator I = prior(CurMPIter); I->getHash() == CurHash ; --I) {
+       CurMPIter != B && CurMPIter->getHash() == CurHash; --CurMPIter) {
+    for (MPIterator I = std::prev(CurMPIter); I->getHash() == CurHash; --I) {
       unsigned CommonTailLen;
       if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(),
                             minCommonTailLength,
@@ -629,9 +633,9 @@ void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
                                         MachineBasicBlock *SuccBB,
                                         MachineBasicBlock *PredBB) {
   MPIterator CurMPIter, B;
-  for (CurMPIter = prior(MergePotentials.end()), B = MergePotentials.begin();
-       CurMPIter->getHash() == CurHash;
-       --CurMPIter) {
+  for (CurMPIter = std::prev(MergePotentials.end()),
+      B = MergePotentials.begin();
+       CurMPIter->getHash() == CurHash; --CurMPIter) {
     // Put the unconditional branch back, if we need one.
     MachineBasicBlock *CurMBB = CurMPIter->getBlock();
     if (SuccBB && CurMBB != PredBB)
@@ -647,6 +651,7 @@ void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
 /// CreateCommonTailOnlyBlock - None of the blocks to be tail-merged consist
 /// only of the common tail.  Create a block that does by splitting one.
 bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
+                                             MachineBasicBlock *SuccBB,
                                              unsigned maxCommonTailLength,
                                              unsigned &commonTailIndex) {
   commonTailIndex = 0;
@@ -676,7 +681,12 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
   DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
                << maxCommonTailLength);
 
-  MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI);
+  // If the split block unconditionally falls-thru to SuccBB, it will be
+  // merged. In control flow terms it should then take SuccBB's name. e.g. If
+  // SuccBB is an inner loop, the common tail is still part of the inner loop.
+  const BasicBlock *BB = (SuccBB && MBB->succ_size() == 1) ?
+    SuccBB->getBasicBlock() : MBB->getBasicBlock();
+  MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI, BB);
   if (!newMBB) {
     DEBUG(dbgs() << "... failed!");
     return false;
@@ -784,7 +794,7 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
          !SameTails[commonTailIndex].tailIsWholeBlock())) {
       // None of the blocks consist entirely of the common tail.
       // Split a block so that one does.
-      if (!CreateCommonTailOnlyBlock(PredBB,
+      if (!CreateCommonTailOnlyBlock(PredBB, SuccBB,
                                      maxCommonTailLength, commonTailIndex)) {
         RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
         continue;
@@ -857,12 +867,12 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
   // a compile-time infinite loop repeatedly doing and undoing the same
   // transformations.)
 
-  for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
+  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
        I != E; ++I) {
     if (I->pred_size() < 2) continue;
     SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
     MachineBasicBlock *IBB = I;
-    MachineBasicBlock *PredBB = prior(I);
+    MachineBasicBlock *PredBB = std::prev(I);
     MergePotentials.clear();
     for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
            E2 = I->pred_end();
@@ -894,7 +904,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
             continue;
           // This is the QBB case described above
           if (!FBB)
-            FBB = llvm::next(MachineFunction::iterator(PBB));
+            FBB = std::next(MachineFunction::iterator(PBB));
         }
 
         // Failing case: the only way IBB can be reached from PBB is via
@@ -944,7 +954,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
 
     // Reinsert an unconditional branch if needed. The 1 below can occur as a
     // result of removing blocks in TryTailMergeBlocks.
-    PredBB = prior(I);     // this may have been changed in TryTailMergeBlocks
+    PredBB = std::prev(I);     // this may have been changed in TryTailMergeBlocks
     if (MergePotentials.size() == 1 &&
         MergePotentials.begin()->getBlock() != PredBB)
       FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
@@ -963,7 +973,7 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
   // Make sure blocks are numbered in order
   MF.RenumberBlocks();
 
-  for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
+  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
        I != E; ) {
     MachineBasicBlock *MBB = I++;
     MadeChange |= OptimizeBlock(MBB);
@@ -1084,7 +1094,7 @@ ReoptimizeBlock:
 
   // Check to see if we can simplify the terminator of the block before this
   // one.
-  MachineBasicBlock &PrevBB = *prior(MachineFunction::iterator(MBB));
+  MachineBasicBlock &PrevBB = *std::prev(MachineFunction::iterator(MBB));
 
   MachineBasicBlock *PriorTBB = 0, *PriorFBB = 0;
   SmallVector<MachineOperand, 4> PriorCond;
@@ -1383,7 +1393,8 @@ ReoptimizeBlock:
           // B elsewhere
           // next:
           if (CurFallsThru) {
-            MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
+            MachineBasicBlock *NextBB =
+                std::next(MachineFunction::iterator(MBB));
             CurCond.clear();
             TII->InsertBranch(*MBB, NextBB, 0, CurCond, DebugLoc());
           }
@@ -1504,7 +1515,7 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
   // branch from condition setting instruction.
   MachineBasicBlock::iterator PI = Loc;
   --PI;
-  while (PI != MBB->begin() && Loc->isDebugValue())
+  while (PI != MBB->begin() && PI->isDebugValue())
     --PI;
 
   bool IsDef = false;