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[AArch64][GlobalISel] Select immediate fcmp if the zero is on the LHS.

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This commit is contained in:
Amara Emerson 2021-01-15 14:31:03 -08:00
parent d845ab560b
commit fd9f6bd39c
2 changed files with 35 additions and 0 deletions
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8
lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
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@ -4224,6 +4224,14 @@ AArch64InstructionSelector::emitFPCompare(Register LHS, Register RHS,
// to explicitly materialize a constant.
const ConstantFP *FPImm = getConstantFPVRegVal(RHS, MRI);
bool ShouldUseImm = FPImm && (FPImm->isZero() && !FPImm->isNegative());
if (!ShouldUseImm) {
// Try commutating the operands.
const ConstantFP *LHSImm = getConstantFPVRegVal(LHS, MRI);
if (LHSImm && (LHSImm->isZero() && !LHSImm->isNegative())) {
ShouldUseImm = true;
std::swap(LHS, RHS);
}
}
unsigned CmpOpcTbl[2][2] = {{AArch64::FCMPSrr, AArch64::FCMPDrr},
{AArch64::FCMPSri, AArch64::FCMPDri}};
unsigned CmpOpc = CmpOpcTbl[ShouldUseImm][OpSize == 64];

27
test/CodeGen/AArch64/GlobalISel/select-fcmp.mir
View File

@ -107,3 +107,30 @@ body: |
%3:gpr(s32) = G_FCMP floatpred(oeq), %0(s64), %2
$s0 = COPY %3(s32)
RET_ReallyLR implicit $s0
...
---
name: zero_lhs
alignment: 4
legalized: true
regBankSelected: true
tracksRegLiveness: true
body: |
bb.1:
liveins: $s0, $s1
; CHECK-LABEL: name: zero_lhs
; CHECK: liveins: $s0, $s1
; CHECK: [[COPY:%[0-9]+]]:fpr32 = COPY $s0
; CHECK: FCMPSri [[COPY]], implicit-def $nzcv
; CHECK: [[CSINCWr:%[0-9]+]]:gpr32 = CSINCWr $wzr, $wzr, 1, implicit $nzcv
; CHECK: $s0 = COPY [[CSINCWr]]
; CHECK: RET_ReallyLR implicit $s0
%0:fpr(s32) = COPY $s0
%1:fpr(s32) = COPY $s1
%2:fpr(s32) = G_FCONSTANT float 0.000000e+00
%3:gpr(s32) = G_FCMP floatpred(oeq), %2(s32), %0
$s0 = COPY %3(s32)
RET_ReallyLR implicit $s0
...