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Use an early return instead of a long if block. 

llvm-svn: 128196
This commit is contained in:
Cameron Zwarich 2011-03-24 04:52:07 +00:00
parent dd84bcce8f
commit 0e331c05ae
1 changed files with 55 additions and 55 deletions
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110
llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
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@ -597,67 +597,67 @@ bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
if (!V) if (!V)
return false; return false;
if (PHINode *PN = dyn_cast<PHINode>(V)) { PHINode *PN = dyn_cast<PHINode>(V);
BasicBlock *BB = RI->getParent(); if (!PN)
if (PN->getParent() != BB) return false;
return false;
// It's not safe to eliminate the sign / zero extension of the return value. BasicBlock *BB = RI->getParent();
// See llvm::isInTailCallPosition(). if (PN->getParent() != BB)
const Function *F = BB->getParent(); return false;
unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
return false;
// Make sure there are no instructions between PHI and return. // It's not safe to eliminate the sign / zero extension of the return value.
BasicBlock::iterator BI = PN; // See llvm::isInTailCallPosition().
do { ++BI; } while (isa<DbgInfoIntrinsic>(BI)); const Function *F = BB->getParent();
if (&*BI != RI) unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
return false; if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
return false;
/// Only dup the ReturnInst if the CallInst is likely to be emitted as a // Make sure there are no instructions between PHI and return.
/// tail call. BasicBlock::iterator BI = PN;
SmallVector<CallInst*, 4> TailCalls; do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) { if (&*BI != RI)
CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I)); return false;
// Make sure the phi value is indeed produced by the tail call.
if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
TLI->mayBeEmittedAsTailCall(CI))
TailCalls.push_back(CI);
}
bool Changed = false; /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) { /// call.
CallInst *CI = TailCalls[i]; SmallVector<CallInst*, 4> TailCalls;
CallSite CS(CI); for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
// Conservatively require the attributes of the call to match those of // Make sure the phi value is indeed produced by the tail call.
// the return. Ignore noalias because it doesn't affect the call sequence. if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
unsigned CalleeRetAttr = CS.getAttributes().getRetAttributes(); TLI->mayBeEmittedAsTailCall(CI))
if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias) TailCalls.push_back(CI);
continue;
// Make sure the call instruction is followed by an unconditional branch
// to the return block.
BasicBlock *CallBB = CI->getParent();
BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
continue;
// Duplicate the return into CallBB.
(void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
UpdateDT = Changed = true;
++NumRetsDup;
}
// If we eliminated all predecessors of the block, delete the block now.
if (Changed && pred_begin(BB) == pred_end(BB))
BB->eraseFromParent();
return Changed;
} }
return false; bool Changed = false;
for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
CallInst *CI = TailCalls[i];
CallSite CS(CI);
// Conservatively require the attributes of the call to match those of the
// return. Ignore noalias because it doesn't affect the call sequence.
unsigned CalleeRetAttr = CS.getAttributes().getRetAttributes();
if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
continue;
// Make sure the call instruction is followed by an unconditional branch to
// the return block.
BasicBlock *CallBB = CI->getParent();
BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
continue;
// Duplicate the return into CallBB.
(void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
UpdateDT = Changed = true;
++NumRetsDup;
}
// If we eliminated all predecessors of the block, delete the block now.
if (Changed && pred_begin(BB) == pred_end(BB))
BB->eraseFromParent();
return Changed;
} }
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//