From ae0a144c39b5735b6bec82b9d385ac3671ef37ff Mon Sep 17 00:00:00 2001 From: Dale Johannesen Date: Sat, 5 Jun 2010 00:30:45 +0000 Subject: [PATCH] Fix some liveout handling related to tail calls, see comments. I don't think this ever resulted in problems on x86, but it would on ARM. llvm-svn: 105509 --- lib/CodeGen/LiveVariables.cpp | 7 ++++++- lib/Target/X86/X86ISelLowering.cpp | 17 ++++++----------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp index 079684eea07..fe6b290ea9f 100644 --- a/lib/CodeGen/LiveVariables.cpp +++ b/lib/CodeGen/LiveVariables.cpp @@ -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 diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index eef773e2338..81f5b19479a 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -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 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()); }