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Allow all types of callee's to be tail called. But avoid automatic tailcall if the callee is a result of bitcast to avoid losing necessary zext / sext etc.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95195 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2010-02-03 03:28:02 +00:00
parent 1611ebbbff
commit 86809ccdad
4 changed files with 38 additions and 24 deletions
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13
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@@ -4197,8 +4197,9 @@ SelectionDAGBuilder::visitIntrinsicCall(CallInst &I, unsigned Intrinsic) {
///
/// This function only tests target-independent requirements.
static bool
isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
isInTailCallPosition(CallSite CS, Attributes CalleeRetAttr,
const TargetLowering &TLI) {
const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
@@ -4207,6 +4208,12 @@ isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
// The block must end in a return statement or an unreachable.
if (!Ret && !isa<UnreachableInst>(Term)) return false;
// Unless we are explicitly forcing tailcall optimization do not tailcall if
// the called function is bitcast'ed. The analysis may not be entirely
// accurate.
if (!PerformTailCallOpt && isa<BitCastInst>(CS.getCalledValue()))
return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
@@ -4348,9 +4355,7 @@ void SelectionDAGBuilder::LowerCallTo(CallSite CS, SDValue Callee,
// Check if target-independent constraints permit a tail call here.
// Target-dependent constraints are checked within TLI.LowerCallTo.
if (isTailCall &&
!isInTailCallPosition(CS.getInstruction(),
CS.getAttributes().getRetAttributes(),
TLI))
!isInTailCallPosition(CS, CS.getAttributes().getRetAttributes(), TLI))
isTailCall = false;
std::pair<SDValue,SDValue> Result =