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rearrange some logic, no functionality change.

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llvm-svn: 157796
This commit is contained in:
Chris Lattner 2012-06-01 05:01:15 +00:00
parent f4a7be0c55
commit 99d5a0bfde
1 changed files with 32 additions and 24 deletions
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56
lib/CodeGen/Analysis.cpp
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@ -203,6 +203,35 @@ ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
}
}
/// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
/// through it (and any transitive noop operands to it) and return its input
/// value. This is used to determine if a tail call can be formed.
///
static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
// If V is not an instruction, it can't be looked through.
const Instruction *U = dyn_cast<Instruction>(V);
if (U == 0 || !U->hasOneUse()) return V;
// Look through truly no-op truncates.
if (isa<TruncInst>(U) &&
TLI.isTruncateFree(U->getOperand(0)->getType(), U->getType()))
return getNoopInput(U->getOperand(0), TLI);
// Look through truly no-op bitcasts.
if (isa<BitCastInst>(U)) {
Value *Op = U->getOperand(0);
if (Op->getType() == U->getType() || // No type change.
// Pointer to pointer cast.
(Op->getType()->isPointerTy() && U->getType()->isPointerTy()))
return getNoopInput(Op, TLI);
}
// Otherwise it's not something we can look through.
return V;
}
/// Test if the given instruction is in a position to be optimized
/// with a tail-call. This roughly means that it's in a block with
/// a return and there's nothing that needs to be scheduled
@ -226,7 +255,8 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
// been fully understood.
if (!Ret &&
(!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
!isa<UnreachableInst>(Term))) return false;
!isa<UnreachableInst>(Term)))
return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
@ -264,29 +294,7 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
return false;
// Otherwise, make sure the unmodified return value of I is the return value.
for (const Instruction *U = dyn_cast<Instruction>(Ret->getOperand(0)); ;
U = dyn_cast<Instruction>(U->getOperand(0))) {
if (!U)
return false;
if (!U->hasOneUse())
return false;
if (U == I)
break;
// Check for a truly no-op truncate.
if (isa<TruncInst>(U) &&
TLI.isTruncateFree(U->getOperand(0)->getType(), U->getType()))
continue;
// Check for a truly no-op bitcast.
if (isa<BitCastInst>(U) &&
(U->getOperand(0)->getType() == U->getType() ||
(U->getOperand(0)->getType()->isPointerTy() &&
U->getType()->isPointerTy())))
continue;
// Otherwise it's not a true no-op.
return false;
}
return true;
return getNoopInput(Ret->getOperand(0), TLI) == I;
}
bool llvm::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,