1 files changed, 68 insertions, 6 deletions

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 2128da1b8aac..b8d9a1a29edc 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -24,6 +24,7 @@
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
@@ -601,8 +602,7 @@ static bool ProfitableToMerge(MachineBasicBlock *MBB1,
   // instructions that would be deleted in the merge.
   MachineFunction *MF = MBB1->getParent();
   if (EffectiveTailLen >= 2 &&
-      MF->getFunction()->getAttributes().
-        hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize) &&
+      MF->getFunction()->hasFnAttribute(Attribute::OptimizeForSize) &&
       (I1 == MBB1->begin() || I2 == MBB2->begin()))
     return true;
 
@@ -728,6 +728,62 @@ bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
   return true;
 }
 
+static bool hasIdenticalMMOs(const MachineInstr *MI1, const MachineInstr *MI2) {
+  auto I1 = MI1->memoperands_begin(), E1 = MI1->memoperands_end();
+  auto I2 = MI2->memoperands_begin(), E2 = MI2->memoperands_end();
+  if ((E1 - I1) != (E2 - I2))
+    return false;
+  for (; I1 != E1; ++I1, ++I2) {
+    if (**I1 != **I2)
+      return false;
+  }
+  return true;
+}
+
+static void
+removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos,
+                               MachineBasicBlock &MBBCommon) {
+  // Remove MMOs from memory operations in the common block
+  // when they do not match the ones from the block being tail-merged.
+  // This ensures later passes conservatively compute dependencies.
+  MachineBasicBlock *MBB = MBBIStartPos->getParent();
+  // Note CommonTailLen does not necessarily matches the size of
+  // the common BB nor all its instructions because of debug
+  // instructions differences.
+  unsigned CommonTailLen = 0;
+  for (auto E = MBB->end(); MBBIStartPos != E; ++MBBIStartPos)
+    ++CommonTailLen;
+
+  MachineBasicBlock::reverse_iterator MBBI = MBB->rbegin();
+  MachineBasicBlock::reverse_iterator MBBIE = MBB->rend();
+  MachineBasicBlock::reverse_iterator MBBICommon = MBBCommon.rbegin();
+  MachineBasicBlock::reverse_iterator MBBIECommon = MBBCommon.rend();
+
+  while (CommonTailLen--) {
+    assert(MBBI != MBBIE && "Reached BB end within common tail length!");
+    (void)MBBIE;
+
+    if (MBBI->isDebugValue()) {
+      ++MBBI;
+      continue;
+    }
+
+    while ((MBBICommon != MBBIECommon) && MBBICommon->isDebugValue())
+      ++MBBICommon;
+
+    assert(MBBICommon != MBBIECommon &&
+           "Reached BB end within common tail length!");
+    assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!");
+
+    if (MBBICommon->mayLoad() || MBBICommon->mayStore())
+      if (!hasIdenticalMMOs(&*MBBI, &*MBBICommon))
+        MBBICommon->clearMemRefs();
+
+    ++MBBI;
+    ++MBBICommon;
+  }
+}
+
 // See if any of the blocks in MergePotentials (which all have a common single
 // successor, or all have no successor) can be tail-merged.  If there is a
 // successor, any blocks in MergePotentials that are not tail-merged and
@@ -762,7 +818,7 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
 
   // Sort by hash value so that blocks with identical end sequences sort
   // together.
-  std::stable_sort(MergePotentials.begin(), MergePotentials.end());
+  array_pod_sort(MergePotentials.begin(), MergePotentials.end());
 
   // Walk through equivalence sets looking for actual exact matches.
   while (MergePotentials.size() > 1) {
@@ -841,6 +897,8 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
         continue;
       DEBUG(dbgs() << "BB#" << SameTails[i].getBlock()->getNumber()
                    << (i == e-1 ? "" : ", "));
+      // Remove MMOs from memory operations as needed.
+      removeMMOsFromMemoryOperations(SameTails[i].getTailStartPos(), *MBB);
       // Hack the end off BB i, making it jump to BB commonTailIndex instead.
       ReplaceTailWithBranchTo(SameTails[i].getTailStartPos(), MBB);
       // BB i is no longer a predecessor of SuccBB; remove it from the worklist.
@@ -1145,6 +1203,11 @@ ReoptimizeBlock:
 
     if (FallThrough == MF.end()) {
       // TODO: Simplify preds to not branch here if possible!
+    } else if (FallThrough->isLandingPad()) {
+      // Don't rewrite to a landing pad fallthough.  That could lead to the case
+      // where a BB jumps to more than one landing pad.
+      // TODO: Is it ever worth rewriting predecessors which don't already
+      // jump to a landing pad, and so can safely jump to the fallthrough?
     } else {
       // Rewrite all predecessors of the old block to go to the fallthrough
       // instead.
@@ -1620,8 +1683,7 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
   // Also avoid moving code above predicated instruction since it's hard to
   // reason about register liveness with predicated instruction.
   bool DontMoveAcrossStore = true;
-  if (!PI->isSafeToMove(TII, nullptr, DontMoveAcrossStore) ||
-      TII->isPredicated(PI))
+  if (!PI->isSafeToMove(nullptr, DontMoveAcrossStore) || TII->isPredicated(PI))
     return MBB->end();
 
 
@@ -1759,7 +1821,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
       break;
 
     bool DontMoveAcrossStore = true;
-    if (!TIB->isSafeToMove(TII, nullptr, DontMoveAcrossStore))
+    if (!TIB->isSafeToMove(nullptr, DontMoveAcrossStore))
       break;
 
     // Remove kills from LocalDefsSet, these registers had short live ranges.