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[PowerPC] Don't remove self VSX copies in PPCInstrInfo::copyPhysReg

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Because of how the allocation of VSX registers interacts with the call-lowering
code, we sometimes end up generating self VSX copies. Specifically, things like
this:
  %VSL2<def> = COPY %F2, %VSL2<imp-use,kill>
(where %F2 is really a sub-register of %VSL2, and so this copy is a nop)

The problem is that ExpandPostRAPseudos always assumes that *some* instruction
has been inserted, and adds implicit defs to it. This is a problem if no copy
was inserted because it can cause subtle problems during post-RA scheduling.
These self copies will have to be removed some other way.

llvm-svn: 204976
This commit is contained in:
Hal Finkel 2014-03-27 22:46:28 +00:00
parent dfb76375a4
commit ee610c3b4d
1 changed files with 13 additions and 9 deletions
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22
lib/Target/PowerPC/PPCInstrInfo.cpp
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@ -51,6 +51,10 @@ cl::desc("Disable compare instruction optimization"), cl::Hidden);
static cl::opt<bool> DisableVSXFMAMutate("disable-ppc-vsx-fma-mutation",
cl::desc("Disable VSX FMA instruction mutation"), cl::Hidden);
static cl::opt<bool> VSXSelfCopyCrash("crash-on-ppc-vsx-self-copy",
cl::desc("Causes the backend to crash instead of generating a nop VSX copy"),
cl::Hidden);
// Pin the vtable to this file.
void PPCInstrInfo::anchor() {}
@ -679,15 +683,15 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
unsigned DestReg, unsigned SrcReg,
bool KillSrc) const {
// We can end up with self copies and similar things as a result of VSX copy
// legalization. Promote (or just ignore) them here.
// legalization. Promote them here.
const TargetRegisterInfo *TRI = &getRegisterInfo();
if (PPC::F8RCRegClass.contains(DestReg) &&
PPC::VSLRCRegClass.contains(SrcReg)) {
unsigned SuperReg =
TRI->getMatchingSuperReg(DestReg, PPC::sub_64, &PPC::VSRCRegClass);
if (SrcReg == SuperReg)
return;
if (VSXSelfCopyCrash && SrcReg == SuperReg)
llvm_unreachable("nop VSX copy");
DestReg = SuperReg;
} else if (PPC::VRRCRegClass.contains(DestReg) &&
@ -695,8 +699,8 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
unsigned SuperReg =
TRI->getMatchingSuperReg(DestReg, PPC::sub_128, &PPC::VSRCRegClass);
if (SrcReg == SuperReg)
return;
if (VSXSelfCopyCrash && SrcReg == SuperReg)
llvm_unreachable("nop VSX copy");
DestReg = SuperReg;
} else if (PPC::F8RCRegClass.contains(SrcReg) &&
@ -704,8 +708,8 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
unsigned SuperReg =
TRI->getMatchingSuperReg(SrcReg, PPC::sub_64, &PPC::VSRCRegClass);
if (DestReg == SuperReg)
return;
if (VSXSelfCopyCrash && DestReg == SuperReg)
llvm_unreachable("nop VSX copy");
SrcReg = SuperReg;
} else if (PPC::VRRCRegClass.contains(SrcReg) &&
@ -713,8 +717,8 @@ void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
unsigned SuperReg =
TRI->getMatchingSuperReg(SrcReg, PPC::sub_128, &PPC::VSRCRegClass);
if (DestReg == SuperReg)
return;
if (VSXSelfCopyCrash && DestReg == SuperReg)
llvm_unreachable("nop VSX copy");
SrcReg = SuperReg;
}