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clang driver: enable fast unaligned access for Android on RISCV64 #85704

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Merged
merged 1 commit into from
Mar 20, 2024
Merged

clang driver: enable fast unaligned access for Android on RISCV64 #85704

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4 changes: 4 additions & 0 deletions clang/lib/Driver/ToolChains/Arch/RISCV.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,10 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
Features.push_back("-relax");
}

// Android requires fast unaligned access on RISCV64.
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This adds two +fast-unaligned-access if -mno-strict-align is specified. Best to update the following AddTargetFeature in case -mstrict-align is specified.

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./bin/clang -mabi=lp64d --target=riscv64-linux-android -### -fsyntax-only ../clang/test/Driver/riscv-features.c -mno-strict-align

prints only one "-target-feature" "+fast-unaligned-access"

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AIUI, it seems common to add target-features as requested and then at the end tools::unifyTargetFeatures normalizes the flags.

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I think the concern is that -target riscv64-linux-android -mstrict-align will add +fast-unaligned-access and -fast-unaligned-access - which would not be handled correctly by unifyTargetFeatures.

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Added a test to check that following -mstrict-align would disable fast unaligned access.

if (Triple.isAndroid())
Features.push_back("+fast-unaligned-access");

// -mstrict-align is default, unless -mno-strict-align is specified.
AddTargetFeature(Args, Features, options::OPT_mno_strict_align,
options::OPT_mstrict_align, "fast-unaligned-access");
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6 changes: 4 additions & 2 deletions clang/test/Driver/riscv-features.c
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@@ -1,7 +1,9 @@
// RUN: %clang --target=riscv32-unknown-elf -### %s -fsyntax-only 2>&1 | FileCheck %s
// RUN: %clang --target=riscv64-unknown-elf -### %s -fsyntax-only 2>&1 | FileCheck %s
// RUN: %clang --target=riscv64-linux-android -### %s -fsyntax-only 2>&1 | FileCheck %s -check-prefixes=ANDROID,DEFAULT
// RUN: %clang -mabi=lp64d --target=riscv64-linux-android -### %s -fsyntax-only 2>&1 | FileCheck %s -check-prefixes=ANDROID,DEFAULT
// RUN: %clang --target=riscv64-linux-android -### %s -fsyntax-only 2>&1 | FileCheck %s -check-prefixes=ANDROID,DEFAULT,FAST-UNALIGNED-ACCESS
// RUN: %clang -mabi=lp64d --target=riscv64-linux-android -### %s -fsyntax-only 2>&1 | FileCheck %s -check-prefixes=ANDROID,DEFAULT,FAST-UNALIGNED-ACCESS
// RUN: %clang -mabi=lp64d --target=riscv64-linux-android -mstrict-align -### %s -fsyntax-only 2>&1 | FileCheck %s -check-prefixes=NO-FAST-UNALIGNED-ACCESS


// CHECK: fno-signed-char

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