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[GlobalISel] Don't use G_FPTOSI in G_ISNAN legalization

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As noted in the comments in D108227, using G_FPTOSI produces wrong results for
G_ISNAN. Drop the G_FPTOSI and perform the operation on integer types.

Elsewhere in LLVM, a bitcast would be the appropriate choice (as it is in SDAG).
GlobalISel does not distinguish between integer and FP types, so a bitcast would
be meaningless here.
This commit is contained in:
Jessica Paquette 2021-08-31 10:23:17 -07:00
parent 22c384129e
commit 94d3ff09cf
2 changed files with 5 additions and 10 deletions
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3
llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
View file

@ -7420,10 +7420,9 @@ LegalizerHelper::LegalizeResult LegalizerHelper::lowerIsNaN(MachineInstr &MI) {
// NaN has all exp bits set and a non zero significand. Therefore:
// isnan(V) == exp mask < abs(V)
auto FPToSI = MIRBuilder.buildFPTOSI(SrcTy, Src);
auto Mask = APInt::getSignedMaxValue(SrcTy.getScalarSizeInBits());
auto MaskCst = MIRBuilder.buildConstant(SrcTy, Mask);
auto AbsV = MIRBuilder.buildAnd(SrcTy, FPToSI, MaskCst);
auto AbsV = MIRBuilder.buildAnd(SrcTy, Src, MaskCst);
auto *FloatTy = getFloatTypeForLLT(MI.getMF()->getFunction().getContext(),
SrcTy.getScalarType());
if (!FloatTy)

12
llvm/test/CodeGen/AArch64/GlobalISel/legalize-isnan.mir
View file

@ -61,10 +61,9 @@ body: |
; CHECK-LABEL: name: scalar_no_flags
; CHECK: liveins: $h0
; CHECK: %val:_(s16) = COPY $h0
; CHECK: [[FPEXT:%[0-9]+]]:_(s32) = G_FPEXT %val(s16)
; CHECK: [[FPTOSI:%[0-9]+]]:_(s32) = G_FPTOSI [[FPEXT]](s32)
; CHECK: [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT %val(s16)
; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 32767
; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[FPTOSI]], [[C]]
; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[ANYEXT]], [[C]]
; CHECK: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 31744
; CHECK: [[SEXT_INREG:%[0-9]+]]:_(s32) = G_SEXT_INREG [[AND]], 16
; CHECK: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(slt), [[C1]](s32), [[SEXT_INREG]]
@ -89,16 +88,13 @@ body: |
; CHECK-LABEL: name: vector_no_flags
; CHECK: liveins: $d0
; CHECK: %val:_(<4 x s16>) = COPY $d0
; CHECK: [[FPTOSI:%[0-9]+]]:_(<4 x s16>) = G_FPTOSI %val(<4 x s16>)
; CHECK: [[C:%[0-9]+]]:_(s16) = G_CONSTANT i16 32767
; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<4 x s16>) = G_BUILD_VECTOR [[C]](s16), [[C]](s16), [[C]](s16), [[C]](s16)
; CHECK: [[AND:%[0-9]+]]:_(<4 x s16>) = G_AND [[FPTOSI]], [[BUILD_VECTOR]]
; CHECK: [[AND:%[0-9]+]]:_(<4 x s16>) = G_AND %val, [[BUILD_VECTOR]]
; CHECK: [[C1:%[0-9]+]]:_(s16) = G_CONSTANT i16 31744
; CHECK: [[BUILD_VECTOR1:%[0-9]+]]:_(<4 x s16>) = G_BUILD_VECTOR [[C1]](s16), [[C1]](s16), [[C1]](s16), [[C1]](s16)
; CHECK: [[ICMP:%[0-9]+]]:_(<4 x s16>) = G_ICMP intpred(slt), [[BUILD_VECTOR1]](<4 x s16>), [[AND]]
; CHECK: %isnan:_(<4 x s1>) = G_TRUNC [[ICMP]](<4 x s16>)
; CHECK: %ext:_(<4 x s16>) = G_ANYEXT %isnan(<4 x s1>)
; CHECK: $d0 = COPY %ext(<4 x s16>)
; CHECK: $d0 = COPY [[ICMP]](<4 x s16>)
; CHECK: RET_ReallyLR implicit $d0
%val:_(<4 x s16>) = COPY $d0
%isnan:_(<4 x s1>) = G_ISNAN %val(<4 x s16>)