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Try to fix an SDAG dependence issue with sret

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r208453 added support for having sret on the second parameter.  In that
change, the code for copying sret into a virtual register was hoisted
into the loop that lowers formal parameters.  This caused a "Wrong
topological sorting" assertion failure during scheduling when a
parameter is passed in memory.  This change undoes that by creating a
second loop that deals with sret.

I'm worried that this fix is incomplete.  I don't fully understand the
dependence issues.  However, with this change we produce the same DAGs
we used to produce, so if they are broken, they are just as broken as
they have always been.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208637 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Kleckner 2014-05-12 22:01:27 +00:00
parent 03e19bb235
commit 17335ce80f
3 changed files with 41 additions and 18 deletions

8
lib/Target/Mips/MipsISelLowering.cpp

@ -2660,20 +2660,22 @@ MipsTargetLowering::LowerFormalArguments(SDValue Chain,
InVals.push_back(Load);
OutChains.push_back(Load.getValue(1));
}
}
for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
// The mips ABIs for returning structs by value requires that we copy
// the sret argument into $v0 for the return. Save the argument into
// a virtual register so that we can access it from the return points.
if (Flags.isSRet()) {
if (Ins[i].Flags.isSRet()) {
unsigned Reg = MipsFI->getSRetReturnReg();
if (!Reg) {
Reg = MF.getRegInfo().createVirtualRegister(
getRegClassFor(isN64() ? MVT::i64 : MVT::i32));
MipsFI->setSRetReturnReg(Reg);
}
SDValue Copy =
DAG.getCopyToReg(DAG.getEntryNode(), DL, Reg, InVals.back());
SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), DL, Reg, InVals[i]);
Chain = DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Copy, Chain);
break;
}
}

33
lib/Target/X86/X86ISelLowering.cpp

@ -2299,23 +2299,26 @@ X86TargetLowering::LowerFormalArguments(SDValue Chain,
MachinePointerInfo(), false, false, false, 0);
InVals.push_back(ArgValue);
}
// The x86-64 ABIs require that for returning structs by value we copy
// the sret argument into %rax/%eax (depending on ABI) for the return.
// Win32 requires us to put the sret argument to %eax as well.
// Save the argument into a virtual register so that we can access it
// from the return points.
if (Ins[i].Flags.isSRet() &&
(Subtarget->is64Bit() || Subtarget->isTargetKnownWindowsMSVC())) {
unsigned Reg = FuncInfo->getSRetReturnReg();
if (!Reg) {
MVT PtrTy = getPointerTy();
Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
FuncInfo->setSRetReturnReg(Reg);
if (Subtarget->is64Bit() || Subtarget->isTargetKnownWindowsMSVC()) {
for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
// The x86-64 ABIs require that for returning structs by value we copy
// the sret argument into %rax/%eax (depending on ABI) for the return.
// Win32 requires us to put the sret argument to %eax as well.
// Save the argument into a virtual register so that we can access it
// from the return points.
if (Ins[i].Flags.isSRet()) {
unsigned Reg = FuncInfo->getSRetReturnReg();
if (!Reg) {
MVT PtrTy = getPointerTy();
Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
FuncInfo->setSRetReturnReg(Reg);
}
SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[i]);
Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
break;
}
SDValue Copy =
DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals.back());
Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
}
}

18
test/CodeGen/X86/x86-64-sret-return-2.ll Normal file

@ -0,0 +1,18 @@
; RUN: llc -mtriple=x86_64-apple-darwin8 < %s | FileCheck %s
; RUN: llc -mtriple=x86_64-pc-linux < %s | FileCheck %s
; FIXME: x32 doesn't know how to select this. This isn't a regression, it never
; worked.
; RUNX: llc -mtriple=x86_64-pc-linux-gnux32 < %s | FileCheck -check-prefix=X32ABI %s
; This used to crash due to topological sorting issues in selection DAG.
define void @foo(i32* sret %agg.result, i32, i32, i32, i32, i32, void (i32)* %pred) {
entry:
call void %pred(i32 undef)
ret void
; CHECK-LABEL: foo:
; CHECK: callq
; CHECK: movq {{.*}}, %rax
; CHECK: ret
}