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[clang] deduplicate target-features for modules #187614

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Merged
fmayer merged 1 commit into from
Apr 8, 2026
+24 −0
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[clang] deduplicate target-features for modules #187614

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3 changes: 3 additions & 0 deletions clang/lib/Serialization/ASTReader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -495,7 +495,10 @@ static bool checkTargetOptions(const TargetOptions &TargetOpts,
SmallVector<StringRef, 4> ReadFeatures(TargetOpts.FeaturesAsWritten.begin(),
TargetOpts.FeaturesAsWritten.end());
llvm::sort(ExistingFeatures);
ExistingFeatures.erase(llvm::unique(ExistingFeatures),
ExistingFeatures.end());
llvm::sort(ReadFeatures);
ReadFeatures.erase(llvm::unique(ReadFeatures), ReadFeatures.end());
Comment on lines 497 to +501

@Bigcheese Bigcheese Mar 31, 2026

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I would prefer we unique these during AST writing, or even in the CompilerInvocation directly. That would also handle the case for dependency scanning.

@fmayer fmayer Mar 31, 2026

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See #187624 (comment) for the reasoning I did it like this. I don't have strong feelings but wanted to do the minimal change here.

@fmayer fmayer Mar 31, 2026

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I guess implicit in this was: I don't think we should dedup in a member called AsWritten

@jansvoboda11 jansvoboda11 Apr 1, 2026

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Would it be possible to remove the AsWritten member entirely, perform this canonicalization during command-line parsing and switch to using Features everywhere?

@fmayer fmayer Apr 1, 2026

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As mentioned in the linked comment, that is an option but makes the error messages more verbose

@jansvoboda11 jansvoboda11 Apr 1, 2026

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Can you explain why? Do targets inject features enabled by default into TargetOptions?

@fmayer fmayer Apr 1, 2026

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my (cursory) understanding is that e.g. +sse2 also implicitly +sse


// We compute the set difference in both directions explicitly so that we can
// diagnose the differences differently.
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21 changes: 21 additions & 0 deletions clang/test/Modules/merge-target-features.cpp
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Expand Up @@ -10,6 +10,15 @@
// RUN: -target-cpu i386 -target-feature +sse2 \
// RUN: Inputs/merge-target-features/module.modulemap
//
// RUN: %clang_cc1 -fmodules -x c++ -fmodules-cache-path=%t \
// RUN: -iquote Inputs/merge-target-features \
// RUN: -fno-implicit-modules \
// RUN: -fmodule-map-file-home-is-cwd \
// RUN: -emit-module -fmodule-name=foo -o %t/foo-double.pcm \
// RUN: -triple i386-unknown-unknown \
// RUN: -target-cpu i386 -target-feature +sse2 -target-feature +sse2 \
// RUN: Inputs/merge-target-features/module.modulemap
//
// RUN: not %clang_cc1 -fmodules -x c++ -fmodules-cache-path=%t \
// RUN: -iquote Inputs/merge-target-features \
// RUN: -fno-implicit-modules \
Expand Down Expand Up @@ -60,6 +69,18 @@
// MISMATCH: error: precompiled file '{{.*}}foo.pcm' was compiled with the target feature '+sse2' but the current translation unit is not
// MISMATCH: error: current translation unit is compiled with the target feature '+cx16' but the precompiled file '{{.*}}foo.pcm' was not
// MISMATCH: error: {{.*}} configuration mismatch
//
// RUN: %clang_cc1 -fmodules -x c++ -fmodules-cache-path=%t \
// RUN: -iquote Inputs/merge-target-features \
// RUN: -fno-implicit-modules \
// RUN: -fmodule-map-file-home-is-cwd \
// RUN: -fmodule-map-file=Inputs/merge-target-features/module.modulemap \
// RUN: -fmodule-file=%t/foo-double.pcm \
// RUN: -triple i386-unknown-unknown \
// RUN: -target-cpu i386 -target-feature +sse2 \
// RUN: -fsyntax-only merge-target-features.cpp 2>&1 \
// RUN: | FileCheck --allow-empty --check-prefix=DOUBLE %s
// DOUBLE-NOT: error:

#include "foo.h"

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