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Simplify and fix incorrect comment. No functionality change. 

llvm-svn: 208272
This commit is contained in:
Richard Smith 2014-05-08 01:08:43 +00:00
parent 095d9d573a
commit c45f3f7433
1 changed files with 14 additions and 21 deletions
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35
llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
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@ -136,18 +136,20 @@ void TailCallElim::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetTransformInfo>();
}
/// CanTRE - Scan the specified basic block for alloca instructions.
/// If it contains any that are variable-sized or not in the entry block,
/// returns false.
static bool CanTRE(AllocaInst *AI) {
// Because of PR962, we don't TRE allocas outside the entry block.
/// \brief Scan the specified function for alloca instructions.
/// If it contains any dynamic allocas, returns false.
static bool CanTRE(Function &F) {
// Because of PR962, we don't TRE dynamic allocas.
for (auto &BB : F) {
for (auto &I : BB) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
if (!AI->isStaticAlloca())
return false;
}
}
}
// If this alloca is in the body of the function, or if it is a variable
// sized allocation, we cannot tail call eliminate calls marked 'tail'
// with this mechanism.
BasicBlock *BB = AI->getParent();
return BB == &BB->getParent()->getEntryBlock() &&
isa<ConstantInt>(AI->getArraySize());
return true;
}
bool TailCallElim::runOnFunction(Function &F) {
@ -390,16 +392,7 @@ bool TailCallElim::runTRE(Function &F) {
// marked with the 'tail' attribute, because doing so would cause the stack
// size to increase (real TRE would deallocate variable sized allocas, TRE
// doesn't).
bool CanTRETailMarkedCall = true;
// Find dynamic allocas.
for (Function::iterator BB = F.begin(), EE = F.end(); BB != EE; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
CanTRETailMarkedCall &= CanTRE(AI);
}
}
}
bool CanTRETailMarkedCall = CanTRE(F);
// Change any tail recursive calls to loops.
//