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[clang] Make fp contract(on) not overwrite earlier contract(fast) and CLI --ffp-contract=fast(-honor-pragmas) #169859

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[clang] Make fp contract(on) not overwrite earlier contract(fast) and CLI --ffp-contract=fast(-honor-pragmas) #169859

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mikolaj-pirog Sep 30, 2025
f606693
Merge remote-tracking branch 'other/main' into mpirog/fix-fast-math-p…
mikolaj-pirog Nov 27, 2025
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mikolaj-pirog Nov 27, 2025
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mikolaj-pirog Nov 27, 2025
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8 changes: 7 additions & 1 deletion clang/lib/Sema/SemaAttr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1381,9 +1381,15 @@ void Sema::ActOnPragmaVisibility(const IdentifierInfo* VisType,
void Sema::ActOnPragmaFPContract(SourceLocation Loc,
LangOptions::FPModeKind FPC) {
FPOptionsOverride NewFPFeatures = CurFPFeatureOverrides();
bool HasContractOverride = NewFPFeatures.hasFPContractModeOverride();
auto DefContractMode = getLangOpts().getDefaultFPContractMode();

switch (FPC) {
case LangOptions::FPM_On:
NewFPFeatures.setAllowFPContractWithinStatement();
if ((HasContractOverride &&
NewFPFeatures.getFPContractModeOverride() == LangOptions::FPM_Off) ||
(!HasContractOverride && DefContractMode == LangOptions::FPM_Off))
NewFPFeatures.setAllowFPContractWithinStatement();
break;
case LangOptions::FPM_Fast:
case LangOptions::FPM_FastHonorPragmas:
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21 changes: 12 additions & 9 deletions clang/test/CodeGen/ffp-contract-fhp-pragma-override.cpp
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Expand Up @@ -2,15 +2,16 @@

float fp_contract_on_1(float a, float b, float c) {
// CHECK-LABEL: fp_contract_on_1fff(
// CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
// CHECK: fmul contract float
// CHECK: fadd contract float
#pragma STDC FP_CONTRACT ON
return a * b + c;
}

float fp_contract_on_2(float a, float b, float c) {
// CHECK-LABEL: fp_contract_on_2fff(
// CHECK: fmul float
// CHECK: fadd float
// CHECK: fmul contract float
// CHECK: fadd contract float
#pragma STDC FP_CONTRACT ON
float t = a * b;
return t + c;
Expand Down Expand Up @@ -52,15 +53,16 @@ float fp_contract_default_2(float a, float b, float c) {

float fp_contract_clang_on_1(float a, float b, float c) {
// CHECK-LABEL: fp_contract_clang_on_1fff(
// CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
// CHECK: fmul contract float
// CHECK: fadd contract float
#pragma clang fp contract(on)
return a * b + c;
}

float fp_contract_clang_on_2(float a, float b, float c) {
// CHECK-LABEL: fp_contract_clang_on_2fff(
// CHECK: fmul float
// CHECK: fadd float
// CHECK: fmul contract float
// CHECK: fadd contract float
#pragma clang fp contract(on)
float t = a * b;
return t + c;
Expand Down Expand Up @@ -104,14 +106,15 @@ float fp_contract_clang_fast_2(float a, float b, float c) {

float fp_contract_global_on_1(float a, float b, float c) {
// CHECK-LABEL: fp_contract_global_on_1fff(
// CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
// CHECK: fmul contract float
// CHECK: fadd contract float
return a * b + c;
}

float fp_contract_global_on_2(float a, float b, float c) {
// CHECK-LABEL: fp_contract_global_on_2fff(
// CHECK: fmul float
// CHECK: fadd float
// CHECK: fmul contract float
// CHECK: fadd contract float
float t = a * b;
return t + c;
}
Expand Down
19 changes: 15 additions & 4 deletions clang/test/CodeGen/fp-contract-fast-pragma.cpp
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Expand Up @@ -87,17 +87,28 @@ float fp_contract_6(float a, float b, float c) {
return a * b + c;
}

// 'on' after 'fast' shouldn't disable 'fast'
#pragma clang fp contract(fast)
#pragma clang fp contract(on)
float fp_contract_7(float a, float b, float c) {
// COMMON: _Z13fp_contract_7fff
// CHECK: %[[M:.+]] = fmul contract float %a, %b
// CHECK-NEXT: fadd contract float %[[M]], %c
// STRICT: %[[M:.+]] = tail call contract float @llvm.experimental.constrained.fmul.f32(float %a, float %b, metadata !"round.tonearest", metadata !"fpexcept.strict")
// STRICT-NEXT: tail call contract float @llvm.experimental.constrained.fadd.f32(float %[[M]], float %c, metadata !"round.tonearest", metadata !"fpexcept.strict")
return a * b + c;
}

#pragma clang fp contract(fast)
float fp_contract_7(float a) {
// COMMON: _Z13fp_contract_7f
float fp_contract_8(float a) {
// COMMON: _Z13fp_contract_8f
// CHECK: tail call contract float @llvm.sqrt.f32(float %a)
// STRICT: tail call contract float @llvm.experimental.constrained.sqrt.f32(float %a, metadata !"round.tonearest", metadata !"fpexcept.strict")
return __builtin_sqrtf(a);
}

float fp_contract_8(float a) {
// COMMON: _Z13fp_contract_8f
float fp_contract_9(float a) {
// COMMON: _Z13fp_contract_9f
// CHECK: tail call float @llvm.sqrt.f32(float %a)
// STRICT: tail call float @llvm.experimental.constrained.sqrt.f32(float %a, metadata !"round.tonearest", metadata !"fpexcept.strict")
#pragma clang fp contract(off)
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2 changes: 1 addition & 1 deletion clang/test/CodeGen/fp-function-attrs.cpp
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Expand Up @@ -51,7 +51,7 @@ float test_contract_on_pragma(float a, float b, float c) {

// CHECK: define{{.*}} float @_Z23test_contract_on_pragmafff(float noundef nofpclass(nan inf) %a, float noundef nofpclass(nan inf) %b, float noundef nofpclass(nan inf) %c)
// CHECK: fmul fast float {{%.+}}, {{%.+}}
// CHECK: fadd reassoc nnan ninf nsz arcp afn float {{%.+}}, {{%.+}}
// CHECK: fadd fast float {{%.+}}, {{%.+}}

// CHECK: attributes [[FAST_ATTRS]] = { {{.*}}"no-infs-fp-math"="true" {{.*}}"no-nans-fp-math"="true" "no-signed-zeros-fp-math"="true"{{.*}} }
// CHECK: attributes [[PRECISE_ATTRS]] = { {{.*}}"no-infs-fp-math"="false" {{.*}}"no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false"{{.*}} }
12 changes: 5 additions & 7 deletions clang/test/CodeGenCUDA/fp-contract.cu
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Expand Up @@ -268,8 +268,7 @@ __host__ __device__ float func2(float a, float b, float c) {
// COMMON-LABEL: _Z5func3fff
// NV-OPT-FAST: fma.rn.f32
// NV-OPT-FAST-NEXT: st.param.b32
// NV-OPT-FASTSTD: mul.rn.f32
// NV-OPT-FASTSTD: add.rn.f32
// NV-OPT-FASTSTD: fma.rn.f32
// NV-OPT-FASTSTD-NEXT: st.param.b32
// NV-OPT-ON: mul.rn.f32
// NV-OPT-ON: add.rn.f32
Expand All @@ -278,18 +277,17 @@ __host__ __device__ float func2(float a, float b, float c) {
// NV-OPT-OFF: add.rn.f32
// NV-OPT-OFF-NEXT: st.param.b32

// AMD-OPT-FAST-IR: fmul float
// AMD-OPT-FAST-IR: fadd float
// AMD-OPT-FAST-IR: fmul contract float
// AMD-OPT-FAST-IR: fadd contract float
// AMD-OPT-ON-IR: fmul float
// AMD-OPT-ON-IR: fadd float
// AMD-OPT-OFF-IR: fmul float
// AMD-OPT-OFF-IR: fadd float

// AMD-OPT-FAST: v_fmac_f32_e32
// AMD-OPT-FAST-NEXT: s_setpc_b64
// AMD-OPT-FASTSTD: v_mul_f32_e32
// AMD-OPT-FASTSTD-NEXT: v_add_f32_e32
// AMD-OPT-FASTSTD-NEXT: s_setpc_b64
// AMD-OPT-FASTSTD: v_fmac_f32_e32
// AMD-OPT-FASTSTD: s_setpc_b64
// AMD-OPT-ON: v_mul_f32_e32
// AMD-OPT-ON-NEXT: v_add_f32_e32
// AMD-OPT-ON-NEXT: s_setpc_b64
Expand Down