[PATCH] D121410: Have cpu-specific variants set 'tune-cpu' as an optimization hint

[Andy Kaylor via Phabricator via cfe-commits]

andrew.w.kaylor added inline comments.


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Comment at: clang/lib/CodeGen/CodeGenModule.cpp:2067
+      // favor this processor.
+      TuneCPU = SD->getCPUName(GD.getMultiVersionIndex())->getName();
+    }
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Unfortunately, I don't think it's this easy. The list of names used for cpu_specific doesn't come from the same place as the list of names used by "tune-cpu". For one thing, the cpu_specific names can't contain the '-' character, so we have names like "skylake_avx512" in cpu_specific that would need to be translated to "skylake-avx512" for "tune-cpu". I believe the list of valid names for "tune-cpu" comes from here: https://github.com/llvm/llvm-project/blob/26cd258420c774254cc48330b1f4d23d353baf05/llvm/lib/Support/X86TargetParser.cpp#L294

Also, some of the aliases supported by cpu_specific don't have any corresponding "tune-cpu" name. You happen to have picked one of these for the test. I believe "core_4th_gen_avx" should map to "haswell".


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Comment at: clang/test/CodeGen/attr-cpuspecific-avx-abi.c:28
 // CHECK: attributes #[[V]] = {{.*}}"target-features"="+avx,+avx2,+bmi,+cmov,+crc32,+cx8,+f16c,+fma,+lzcnt,+mmx,+movbe,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87,+xsave"
+// CHECK-SAME: "tune-cpu"="core_4th_gen_avx"
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As noted above, this isn't a valid setting for "tune-cpu". I think it would just be ignored.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D121410/new/

https://reviews.llvm.org/D121410