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Ignore dbg intrinsics while folding switch instruction.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63802 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2009-02-05 00:30:42 +00:00
parent 4be0bdf7c1
commit 2cc86a1de1
2 changed files with 77 additions and 8 deletions
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27
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1330,6 +1330,20 @@ static bool FoldTwoEntryPHINode(PHINode *PN) {
return true;
}
/// isTerminatorFirstRelevantInsn - Return true if Term is very first
/// instruction ignoring Phi nodes and dbg intrinsics.
static bool isTerminatorFirstRelevantInsn(BasicBlock *BB, Instruction *Term) {
BasicBlock::iterator BBI = Term;
while (BBI != BB->begin()) {
--BBI;
if (!isa<DbgInfoIntrinsic>(BBI))
break;
}
if (isa<PHINode>(BBI) || &*BBI == Term)
return true;
return false;
}
/// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes
/// to two returning blocks, try to merge them together into one return,
/// introducing a select if the return values disagree.
@ -1343,12 +1357,10 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
// Check to ensure both blocks are empty (just a return) or optionally empty
// with PHI nodes. If there are other instructions, merging would cause extra
// computation on one path or the other.
BasicBlock::iterator BBI = TrueRet;
if (BBI != TrueSucc->begin() && !isa<PHINode>(--BBI))
return false; // Not empty with optional phi nodes.
BBI = FalseRet;
if (BBI != FalseSucc->begin() && !isa<PHINode>(--BBI))
return false; // Not empty with optional phi nodes.
if (!isTerminatorFirstRelevantInsn(TrueSucc, TrueRet))
return false;
if (!isTerminatorFirstRelevantInsn(FalseSucc, FalseRet))
return false;
// Okay, we found a branch that is going to two return nodes. If
// there is no return value for this function, just change the
@ -1750,8 +1762,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
// different return values, fold the replace the branch/return with a select
// and return.
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
BasicBlock::iterator BBI = BB->getTerminator();
if (BBI == BB->begin() || isa<PHINode>(--BBI)) {
if (isTerminatorFirstRelevantInsn(BB, BB->getTerminator())) {
// Find predecessors that end with branches.
SmallVector<BasicBlock*, 8> UncondBranchPreds;
SmallVector<BranchInst*, 8> CondBranchPreds;