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[ARM] Recognize abi tag module flags #161306

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[ARM] Recognize abi tag module flags #161306

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1e92973
[ARM] Recognize some module flags
paperchalice Sep 29, 2025
0afe4bc
address comments
paperchalice Oct 7, 2025
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28 changes: 22 additions & 6 deletions llvm/lib/Target/ARM/ARMAsmPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -701,9 +701,21 @@ void ARMAsmPrinter::emitAttributes() {
ARMBuildAttrs::AddressDirect);
}

Metadata *MDEx = nullptr;
Metadata *MDDM = nullptr;
Metadata *MDNM = nullptr;
if (const Module *M = MMI->getModule()) {
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Is it ever possible for MMI->getModule() to be nullptr when writing build attributes? In the existing code for checkDenormalConsistency it is universally dereferenced?

If it isn't possible then I think it would be worth moving the M->getModuleFlag() calls closer to where they are used. I find it difficult to tell MDDM and MDNM apart with my eyesight.

For example (using SourceModule instead of M, as SourceModule is used on line 801).

const Module *SourceModule = MMI->getModule();
// Set FP Denormals
Metadata *MDDM = SourceModule->getModuleFlag("arm-eabi-fp-denormal");
if (auto *DM = mdconst::extract_or_null<ConstantInt>(MDDM))
  ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal, DM->getZExtValue());
else if (checkDenormalAttributeConsistency(*SourceModule,
                                             "denormal-fp-math",
                                             DenormalMode::getPreserveSign()))

If we do have to preserve the if (const Module *M = MMI->getModule()) can you expand the MDDM and MDNM a bit? perhaps MDDenorm and MDNumModel .

MDEx = M->getModuleFlag("arm-eabi-fp-exceptions");
MDDM = M->getModuleFlag("arm-eabi-fp-denormal");
MDNM = M->getModuleFlag("arm-eabi-fp-number-model");
}

// Set FP Denormals.
if (checkDenormalAttributeConsistency(*MMI->getModule(), "denormal-fp-math",
DenormalMode::getPreserveSign()))
if (auto *DM = mdconst::extract_or_null<ConstantInt>(MDDM))
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal, DM->getZExtValue());
else if (checkDenormalAttributeConsistency(*MMI->getModule(),
"denormal-fp-math",
DenormalMode::getPreserveSign()))
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal,
ARMBuildAttrs::PreserveFPSign);
else if (checkDenormalAttributeConsistency(*MMI->getModule(),
Expand Down Expand Up @@ -743,9 +755,11 @@ void ARMAsmPrinter::emitAttributes() {
}

// Set FP exceptions and rounding
if (checkFunctionsAttributeConsistency(*MMI->getModule(),
"no-trapping-math", "true") ||
TM.Options.NoTrappingFPMath)
if (auto *Ex = mdconst::extract_or_null<ConstantInt>(MDEx))
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_exceptions, Ex->getZExtValue());
else if (checkFunctionsAttributeConsistency(*MMI->getModule(),
"no-trapping-math", "true") ||
TM.Options.NoTrappingFPMath)
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_exceptions,
ARMBuildAttrs::Not_Allowed);
else {
Expand All @@ -759,7 +773,9 @@ void ARMAsmPrinter::emitAttributes() {

// TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath is the
// equivalent of GCC's -ffinite-math-only flag.
if (TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath)
if (auto *NM = mdconst::extract_or_null<ConstantInt>(MDNM))
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_number_model, NM->getZExtValue());
else if (TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath)
ATS.emitAttribute(ARMBuildAttrs::ABI_FP_number_model,
ARMBuildAttrs::Allowed);
else
Expand Down
14 changes: 14 additions & 0 deletions llvm/test/CodeGen/ARM/build-attributes-module.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
; RUN: llc %s -mtriple=arm-none-none-eabi -o - | FileCheck %s

define void @f() {
ret void
}

!llvm.module.flags = !{!0, !1, !2}

; CHECK: .eabi_attribute 20, 0
!0 = !{i32 2, !"arm-eabi-fp-denormal", i32 0}
; CHECK: .eabi_attribute 21, 1
!1 = !{i32 2, !"arm-eabi-fp-exceptions", i32 1}
; CHECK: .eabi_attribute 23, 1
!2 = !{i32 2, !"arm-eabi-fp-number-model", i32 1}