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[PowerPC] Split out the tailcall calling convention checks. NFC. 

Move the calling convention checks for tail-call eligibility for the 64-bit
SysV ABI into a separate function. This is so that it can be shared with
'mayBeEmittedAsTailCall' in a subsequent change.

llvm-svn: 318305
This commit is contained in:
Sean Fertile 2017-11-15 16:53:41 +00:00
parent ac7e3d6451
commit 7b056b3048
1 changed files with 19 additions and 11 deletions
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30
llvm/lib/Target/PowerPC/PPCISelLowering.cpp
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@ -4392,6 +4392,20 @@ hasSameArgumentList(const Function *CallerFn, ImmutableCallSite CS) {
return true;
}
// Returns true if TCO is possible between the callers and callees
// calling conventions.
static bool
areCallingConvEligibleForTCO_64SVR4(CallingConv::ID CallerCC,
CallingConv::ID CalleeCC) {
// Tail or Sibling call optimization (TCO/SCO) needs callee and caller to
// have the same calling convention.
if (CallerCC != CalleeCC)
return false;
// Tail or Sibling calls can be done with fastcc/ccc.
return (CallerCC == CallingConv::Fast || CallerCC == CallingConv::C);
}
bool
PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(
SDValue Callee,
@ -4408,15 +4422,9 @@ PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(
// Variadic argument functions are not supported.
if (isVarArg) return false;
MachineFunction &MF = DAG.getMachineFunction();
CallingConv::ID CallerCC = MF.getFunction()->getCallingConv();
// Tail or Sibling call optimization (TCO/SCO) needs callee and caller has
// the same calling convention
if (CallerCC != CalleeCC) return false;
// SCO support C calling convention
if (CalleeCC != CallingConv::Fast && CalleeCC != CallingConv::C)
auto *Caller = DAG.getMachineFunction().getFunction();
// Check that the calling conventions are compatible for tco.
if (!areCallingConvEligibleForTCO_64SVR4(Caller->getCallingConv(), CalleeCC))
return false;
// Caller contains any byval parameter is not supported.
@ -4438,7 +4446,7 @@ PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(
// If the caller and callee potentially have different TOC bases then we
// cannot tail call since we need to restore the TOC pointer after the call.
// ref: https://bugzilla.mozilla.org/show_bug.cgi?id=973977
if (!callsShareTOCBase(MF.getFunction(), Callee, getTargetMachine()))
if (!callsShareTOCBase(Caller, Callee, getTargetMachine()))
return false;
// TCO allows altering callee ABI, so we don't have to check further.
@ -4450,7 +4458,7 @@ PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(
// If callee use the same argument list that caller is using, then we can
// apply SCO on this case. If it is not, then we need to check if callee needs
// stack for passing arguments.
if (!hasSameArgumentList(MF.getFunction(), CS) &&
if (!hasSameArgumentList(Caller, CS) &&
needStackSlotPassParameters(Subtarget, Outs)) {
return false;
}