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__builtin_cpu_supports doesn't understand x86-64 micro-architecture levels #59961

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chfast opened this issue Jan 12, 2023 · 4 comments
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__builtin_cpu_supports doesn't understand x86-64 micro-architecture levels #59961

chfast opened this issue Jan 12, 2023 · 4 comments
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backend:X86 clang:frontend Language frontend issues, e.g. anything involving "Sema"

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@chfast
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chfast commented Jan 12, 2023

This does not work: __builtin_cpu_supports("x86-64-v2").
@RKSimon RKSimon added backend:X86 clang:frontend Language frontend issues, e.g. anything involving "Sema" and removed new issue labels Jan 12, 2023
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llvmbot commented Jan 12, 2023

@llvm/issue-subscribers-backend-x86

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llvmbot commented Jan 12, 2023

@llvm/issue-subscribers-clang-frontend

@marxin marxin mentioned this issue Mar 10, 2023
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chfast referenced this issue Aug 24, 2023
@MaskRay
[X86] Support arch=x86-64{,-v2,-v3,-v4} for target_clones attribute
7a41af8 
GCC 12 (https://gcc.gnu.org/PR101696) allows `arch=x86-64`
`arch=x86-64-v2` `arch=x86-64-v3` `arch=x86-64-v4` in the
target_clones function attribute. This patch ports the feature.

* Set KeyFeature to `x86-64{,-v2,-v3,-v4}` in `Processors[]`, to be used
  by X86TargetInfo::multiVersionSortPriority
* builtins: change `__cpu_features2` to an array like libgcc. Define
  `FEATURE_X86_64_{BASELINE,V2,V3,V4}` and depended ISA feature bits.
* CGBuiltin.cpp: update EmitX86CpuSupports to handle `arch=x86-64*`.

Close #55830

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D158329
@MaskRay
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MaskRay commented Aug 25, 2023

Patch: https://reviews.llvm.org/D158811

@ecatmur
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ecatmur commented Dec 25, 2023

This PR appears to imply that [[gnu::target("x86-64-v2")]] should work:

llvm-project/clang/lib/CodeGen/CodeGenFunction.cpp

Lines 2686 to 2689 in 27da153

// If arch= specifies an x86-64 micro-architecture level, test the feature
// with __builtin_cpu_supports, otherwise use __builtin_cpu_is.
if (Arch.starts_with("x86-64"))
Condition = EmitX86CpuSupports({Arch});

However this is not tested, and current trunk does not accept:

<source>:3:36: error: function multiversioning doesn't support architecture 'x86-64'
    3 | [[gnu::target("arch=x86-64")]] int f() { return 2; }
      |                                    ^

This appears to be rejected at

llvm-project/clang/lib/Sema/SemaDecl.cpp

Lines 11066 to 11068 in 966d564

if (!ParseInfo.CPU.empty() && !TargetInfo.validateCpuIs(ParseInfo.CPU)) {
S.Diag(FD->getLocation(), diag::err_bad_multiversion_option)
<< Architecture << ParseInfo.CPU;
Should I report a new issue?

@ecatmur ecatmur mentioned this issue Dec 25, 2023
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@MaskRay @chfast @ecatmur @RKSimon @llvmbot