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PPCInstrInfo::optimizeCompareInstr should not optimize FP compares 

The floating-point record forms on PPC don't set the condition register bits
based on a comparison with zero (like the integer record forms do), but rather
based on the exception status bits.

llvm-svn: 181423
This commit is contained in:
Hal Finkel 2013-05-08 12:16:14 +00:00
parent 5829a98c48
commit 08e53ee551
2 changed files with 13 additions and 20 deletions
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29
llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
View File

@ -1096,8 +1096,11 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
int OpC = CmpInstr->getOpcode();
unsigned CRReg = CmpInstr->getOperand(0).getReg();
bool isFP = OpC == PPC::FCMPUS || OpC == PPC::FCMPUD;
unsigned CRRecReg = isFP ? PPC::CR1 : PPC::CR0;
// FP record forms set CR1 based on the execption status bits, not a
// comparison with zero.
if (OpC == PPC::FCMPUS || OpC == PPC::FCMPUD)
return false;
// The record forms set the condition register based on a signed comparison
// with zero (so says the ISA manual). This is not as straightforward as it
@ -1140,9 +1143,9 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
equalityOnly = true;
} else
return false;
} else if (!isFP)
} else
equalityOnly = is64BitUnsignedCompare;
} else if (!isFP)
} else
equalityOnly = is32BitUnsignedCompare;
if (equalityOnly) {
@ -1211,8 +1214,8 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
unsigned IOpC = Instr.getOpcode();
if (&*I != CmpInstr && (
Instr.modifiesRegister(CRRecReg, TRI) ||
Instr.readsRegister(CRRecReg, TRI)))
Instr.modifiesRegister(PPC::CR0, TRI) ||
Instr.readsRegister(PPC::CR0, TRI)))
// This instruction modifies or uses the record condition register after
// the one we want to change. While we could do this transformation, it
// would likely not be profitable. This transformation removes one
@ -1232,15 +1235,6 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
break;
}
if (isFP && (IOpC == PPC::FSUB || IOpC == PPC::FSUBS) &&
((Instr.getOperand(1).getReg() == SrcReg &&
Instr.getOperand(2).getReg() == SrcReg2) ||
(Instr.getOperand(1).getReg() == SrcReg2 &&
Instr.getOperand(2).getReg() == SrcReg))) {
Sub = &*I;
break;
}
if (I == B)
// The 'and' is below the comparison instruction.
return false;
@ -1286,8 +1280,7 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
// The operands to subf are the opposite of sub, so only in the fixed-point
// case, invert the order.
if (!isFP)
ShouldSwap = !ShouldSwap;
ShouldSwap = !ShouldSwap;
}
if (ShouldSwap)
@ -1326,7 +1319,7 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr,
MachineBasicBlock::iterator MII = MI;
BuildMI(*MI->getParent(), llvm::next(MII), MI->getDebugLoc(),
get(TargetOpcode::COPY), CRReg)
.addReg(CRRecReg, MIOpC != NewOpC ? RegState::Kill : 0);
.addReg(PPC::CR0, MIOpC != NewOpC ? RegState::Kill : 0);
if (MIOpC != NewOpC) {
// We need to be careful here: we're replacing one instruction with

4
llvm/test/CodeGen/PowerPC/optcmp.ll
View File

@ -118,7 +118,7 @@ entry:
ret double %cond
; CHECK: @food
; CHECK: fsub. 0, 1, 2
; CHECK-NOT: fsub. 0, 1, 2
; CHECK: stfd 0, 0(5)
}
@ -131,7 +131,7 @@ entry:
ret float %cond
; CHECK: @foof
; CHECK: fsubs. 0, 1, 2
; CHECK-NOT: fsubs. 0, 1, 2
; CHECK: stfs 0, 0(5)
}