Turns out AnalyzeBranch can modify the mbb being analyzed. This is a nasty

suprise to some callers, e.g. register coalescer. For now, add an parameter
that tells AnalyzeBranch whether it's safe to modify the mbb. A better
solution is out there, but I don't have time to deal with it right now.

llvm-svn: 64124

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Target/Alpha/AlphaInstrInfo.cpp b/llvm/lib/Target/Alpha/AlphaInstrInfo.cpp
index 2c7404d5647..0974699fa0c 100644
--- a/llvm/lib/Target/Alpha/AlphaInstrInfo.cpp
+++ b/llvm/lib/Target/Alpha/AlphaInstrInfo.cpp
@@ -321,8 +321,9 @@ static unsigned AlphaRevCondCode(unsigned Opcode) {
 
 // Branch analysis.
 bool AlphaInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
-                                 MachineBasicBlock *&FBB,
-                                 SmallVectorImpl<MachineOperand> &Cond) const {
+                                   MachineBasicBlock *&FBB,
+                                   SmallVectorImpl<MachineOperand> &Cond,
+                                   bool AllowModify) const {
   // If the block has no terminators, it just falls into the block after it.
   MachineBasicBlock::iterator I = MBB.end();
   if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
@@ -373,7 +374,8 @@ bool AlphaInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TB
       LastInst->getOpcode() == Alpha::BR) {
     TBB = SecondLastInst->getOperand(0).getMBB();
     I = LastInst;
-    I->eraseFromParent();
+    if (AllowModify)
+      I->eraseFromParent();
     return false;
   }