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Fix some liveout handling related to tail calls, see comments.

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I don't think this ever resulted in problems on x86, but it
would on ARM.

llvm-svn: 105509
This commit is contained in:
Dale Johannesen 2010-06-05 00:30:45 +00:00
parent e1853a7473
commit ae0a144c39
2 changed files with 12 additions and 12 deletions
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7
lib/CodeGen/LiveVariables.cpp
View File

@ -609,7 +609,12 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
// Finally, if the last instruction in the block is a return, make sure to
// mark it as using all of the live-out values in the function.
if (!MBB->empty() && MBB->back().getDesc().isReturn()) {
// Things marked both call and return are tail calls; do not do this for
// them. The tail callee need not take the same registers as input
// that it produces as output, and there are dependencies for its input
// registers elsewhere.
if (!MBB->empty() && MBB->back().getDesc().isReturn()
&& !MBB->back().getDesc().isCall()) {
MachineInstr *Ret = &MBB->back();
for (MachineRegisterInfo::liveout_iterator

17
lib/Target/X86/X86ISelLowering.cpp
View File

@ -2150,17 +2150,12 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
Ops.push_back(InFlag);
if (isTailCall) {
// If this is the first return lowered for this function, add the regs
// to the liveout set for the function.
if (MF.getRegInfo().liveout_empty()) {
SmallVector<CCValAssign, 16> RVLocs;
CCState CCInfo(CallConv, isVarArg, getTargetMachine(), RVLocs,
*DAG.getContext());
CCInfo.AnalyzeCallResult(Ins, RetCC_X86);
for (unsigned i = 0; i != RVLocs.size(); ++i)
if (RVLocs[i].isRegLoc())
MF.getRegInfo().addLiveOut(RVLocs[i].getLocReg());
}
// We used to do:
//// If this is the first return lowered for this function, add the regs
//// to the liveout set for the function.
// This isn't right, although it's probably harmless on x86; liveouts
// should be computed from returns not tail calls. Consider a void
// function making a tail call to a function returning int.
return DAG.getNode(X86ISD::TC_RETURN, dl,
NodeTys, &Ops[0], Ops.size());
}