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[Flang][AArch64][VecLib] Add libmvec support for Flang/AArch64 #146453

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Merged
merged 2 commits into from
Jul 3, 2025
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[Flang][AArch64][VecLib] Add libmvec support for Flang/AArch64 #146453

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[Flang][AArch64][VecLib] Add libmvec support for Flang/AArch64
kawashima-fj Jun 25, 2025
9433476
Mention the required GLIBC version in help and release note
kawashima-fj Jul 1, 2025
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3 changes: 2 additions & 1 deletion clang/include/clang/Driver/Options.td
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Expand Up @@ -3487,7 +3487,8 @@ def fno_experimental_isel : Flag<["-"], "fno-experimental-isel">, Group<f_clang_
Alias<fno_global_isel>;
def fveclib : Joined<["-"], "fveclib=">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
HelpText<"Use the given vector functions library">,
HelpText<"Use the given vector functions library.\n"
" Note: -fveclib=libmvec on AArch64 requires GLIBC 2.40 or newer.">,
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Is the constraint on glibc >=2.40 true for clang as well? What happens if the user attempts to build with an older glibc? Will they see a configure-time error or will the build fail?

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Ach. Please ignore the question about the constraint on glibc. The second question about failure modes with older glibc still holds though.

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@paulwalker-arm paulwalker-arm Jul 1, 2025 •
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The toolchain user will see a link time failure when trying to resolve a call to a vector math routine. Note: the exact requirement depends on the function in question, but version 2.40 is what was used when deciding which math functions to add mappings for.

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Yes, a user will see a link-time error message if older glibc is used. This is same as Clang.

$ flang -O2 -fveclib=libmvec test.f90
/usr/bin/ld: /tmp/test-d377a8.o: in function `_QQmain':
FIRModule:(.text+0xd4): undefined reference to `_ZGVnN4vv_powf'
flang-21: error: linker command failed with exit code 1 (use -v to see invocation)

Please see https://github.com/bminor/glibc/blob/96abd59bf2a11ddd4e7ccaac840ec13c0b62d3ba/sysdeps/aarch64/fpu/Versions for math function v.s. required glibc version. Currently, math functions introduced in glibc > 2.40 are not used in -fveclib=libmvec.

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Thank you for the clarification

HelpTextForVariants<[ClangOption, CC1Option],
"Use the given vector functions library.\n"
" Note: -fveclib={ArmPL,SLEEF,libmvec} implies -fno-math-errno.\n"
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9 changes: 8 additions & 1 deletion clang/lib/Driver/ToolChains/Flang.cpp
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Expand Up @@ -484,11 +484,18 @@ void Flang::addTargetOptions(const ArgList &Args,
Triple.getArch() != llvm::Triple::x86_64)
D.Diag(diag::err_drv_unsupported_opt_for_target)
<< Name << Triple.getArchName();
} else if (Name == "libmvec" || Name == "AMDLIBM") {
} else if (Name == "AMDLIBM") {
if (Triple.getArch() != llvm::Triple::x86 &&
Triple.getArch() != llvm::Triple::x86_64)
D.Diag(diag::err_drv_unsupported_opt_for_target)
<< Name << Triple.getArchName();
} else if (Name == "libmvec") {
if (Triple.getArch() != llvm::Triple::x86 &&
Triple.getArch() != llvm::Triple::x86_64 &&
Triple.getArch() != llvm::Triple::aarch64 &&
Triple.getArch() != llvm::Triple::aarch64_be)
D.Diag(diag::err_drv_unsupported_opt_for_target)
<< Name << Triple.getArchName();
} else if (Name == "SLEEF" || Name == "ArmPL") {
if (Triple.getArch() != llvm::Triple::aarch64 &&
Triple.getArch() != llvm::Triple::aarch64_be)
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2 changes: 2 additions & 0 deletions flang/docs/ReleaseNotes.md
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Expand Up @@ -34,6 +34,8 @@ page](https://llvm.org/releases/).

* -floop-interchange is now recognized by flang.
* -floop-interchange is enabled by default at -O2 and above.
* -fveclib=libmvec is supported for AArch64 (same as Flang/x86 and
Clang/AArch64) (requires GLIBC 2.40 or newer)

## Windows Support

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4 changes: 4 additions & 0 deletions flang/test/Driver/fveclib-codegen.f90
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@@ -1,6 +1,8 @@
! test that -fveclib= is passed to the backend
! RUN: %if aarch64-registered-target %{ %flang -S -Ofast -target aarch64-unknown-linux-gnu -fveclib=SLEEF -o - %s | FileCheck %s --check-prefix=SLEEF %}
! RUN: %if x86-registered-target %{ %flang -S -Ofast -target x86_64-unknown-linux-gnu -fveclib=libmvec -o - %s | FileCheck %s %}
! RUN: %if aarch64-registered-target %{ %flang -S -Ofast -target aarch64-unknown-linux-gnu -fveclib=libmvec -march=armv8.2-a+nosve -o - %s | FileCheck %s --check-prefix=LIBMVEC-AARCH64-NEON %}
! RUN: %if aarch64-registered-target %{ %flang -S -Ofast -target aarch64-unknown-linux-gnu -fveclib=libmvec -march=armv8.2-a+sve -o - %s | FileCheck %s --check-prefix=LIBMVEC-AARCH64-SVE %}
! RUN: %if x86-registered-target %{ %flang -S -O3 -ffast-math -target x86_64-unknown-linux-gnu -fveclib=AMDLIBM -o - %s | FileCheck %s --check-prefix=AMDLIBM %}
! RUN: %flang -S -Ofast -fveclib=NoLibrary -o - %s | FileCheck %s --check-prefix=NOLIB

Expand All @@ -11,6 +13,8 @@ subroutine sb(a, b)
! check that we used a vectorized call to powf()
! CHECK: _ZGVbN4vv_powf
! SLEEF: _ZGVnN4vv_powf
! LIBMVEC-AARCH64-NEON: _ZGVnN4vv_powf
! LIBMVEC-AARCH64-SVE: _ZGVsMxvv_powf
! AMDLIBM: amd_vrs4_powf
! NOLIB: powf
a(i) = a(i) ** b(i)
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3 changes: 2 additions & 1 deletion flang/test/Driver/fveclib.f90
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@@ -1,6 +1,7 @@
! RUN: %flang -### -c -fveclib=none %s 2>&1 | FileCheck -check-prefix CHECK-NOLIB %s
! RUN: %flang -### -c -fveclib=Accelerate %s 2>&1 | FileCheck -check-prefix CHECK-ACCELERATE %s
! RUN: %flang -### -c --target=x86_64-unknown-linux-gnu -fveclib=libmvec %s 2>&1 | FileCheck -check-prefix CHECK-libmvec %s
! RUN: %flang -### -c --target=aarch64-unknown-linux-gnu -fveclib=libmvec %s 2>&1 | FileCheck -check-prefix CHECK-libmvec %s
! RUN: %flang -### -c -fveclib=MASSV %s 2>&1 | FileCheck -check-prefix CHECK-MASSV %s
! RUN: %flang -### -c -fveclib=Darwin_libsystem_m %s 2>&1 | FileCheck -check-prefix CHECK-DARWIN_LIBSYSTEM_M %s
! RUN: %flang -### -c --target=aarch64-none-none -fveclib=SLEEF %s 2>&1 | FileCheck -check-prefix CHECK-SLEEF %s
Expand All @@ -23,7 +24,7 @@

! RUN: not %flang --target=x86-none-none -c -fveclib=SLEEF %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! RUN: not %flang --target=x86-none-none -c -fveclib=ArmPL %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! RUN: not %flang --target=aarch64-none-none -c -fveclib=libmvec %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! RUN: not %flang --target=riscv64-none-none -c -fveclib=libmvec %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! RUN: not %flang --target=aarch64-none-none -c -fveclib=SVML %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! RUN: not %flang --target=aarch64-none-none -c -fveclib=AMDLIBM %s 2>&1 | FileCheck -check-prefix CHECK-ERROR %s
! CHECK-ERROR: unsupported option {{.*}} for target
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