Tail merging pass shall not break up IT blocks. rdar://8115404
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106517 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index e17e47a..7f98df0 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -370,6 +370,9 @@
/// iterator. This returns the new MBB.
MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
MachineBasicBlock::iterator BBI1) {
+ if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1))
+ return 0;
+
MachineFunction &MF = *CurMBB.getParent();
// Create the fall-through block.
@@ -614,9 +617,10 @@
/// CreateCommonTailOnlyBlock - None of the blocks to be tail-merged consist
/// only of the common tail. Create a block that does by splitting one.
-unsigned BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
- unsigned maxCommonTailLength) {
- unsigned commonTailIndex = 0;
+bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
+ unsigned maxCommonTailLength,
+ unsigned &commonTailIndex) {
+ commonTailIndex = 0;
unsigned TimeEstimate = ~0U;
for (unsigned i = 0, e = SameTails.size(); i != e; ++i) {
// Use PredBB if possible; that doesn't require a new branch.
@@ -644,6 +648,11 @@
<< maxCommonTailLength);
MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI);
+ if (!newMBB) {
+ DEBUG(dbgs() << "... failed!");
+ return false;
+ }
+
SameTails[commonTailIndex].setBlock(newMBB);
SameTails[commonTailIndex].setTailStartPos(newMBB->begin());
@@ -651,7 +660,7 @@
if (PredBB == MBB)
PredBB = newMBB;
- return commonTailIndex;
+ return true;
}
// See if any of the blocks in MergePotentials (which all have a common single
@@ -746,7 +755,11 @@
!SameTails[commonTailIndex].tailIsWholeBlock())) {
// None of the blocks consist entirely of the common tail.
// Split a block so that one does.
- commonTailIndex = CreateCommonTailOnlyBlock(PredBB, maxCommonTailLength);
+ if (!CreateCommonTailOnlyBlock(PredBB,
+ maxCommonTailLength, commonTailIndex)) {
+ RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
+ continue;
+ }
}
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h
index b087395..15dfa7f 100644
--- a/lib/CodeGen/BranchFolding.h
+++ b/lib/CodeGen/BranchFolding.h
@@ -102,8 +102,9 @@
MachineBasicBlock *PredBB);
void RemoveBlocksWithHash(unsigned CurHash, MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB);
- unsigned CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
- unsigned maxCommonTailLength);
+ bool CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
+ unsigned maxCommonTailLength,
+ unsigned &commonTailIndex);
bool OptimizeBranches(MachineFunction &MF);
bool OptimizeBlock(MachineBasicBlock *MBB);
diff --git a/lib/CodeGen/TargetInstrInfoImpl.cpp b/lib/CodeGen/TargetInstrInfoImpl.cpp
index 53f3ee8..5e145cf 100644
--- a/lib/CodeGen/TargetInstrInfoImpl.cpp
+++ b/lib/CodeGen/TargetInstrInfoImpl.cpp
@@ -28,6 +28,8 @@
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+/// ReplaceTailWithBranchTo - Delete the instruction OldInst and everything
+/// after it, replacing it with an unconditional branch to NewDest.
void
TargetInstrInfoImpl::ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
MachineBasicBlock *NewDest) const {