[clang] [X86][Driver] Do not add `-evex512` for `-march=native` when the target doesn't support AVX512 (PR #91694)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: Phoebe Wang (phoebewang)

<details>
<summary>Changes</summary>

Users want `-march=sandybridge -mavx512f -mavx512vl` behaves the same as `-march=native -mavx512f -mavx512vl` on a sandybridge target.

Fixes: #<!-- -->91076

---
Full diff: https://github.com/llvm/llvm-project/pull/91694.diff


1 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Arch/X86.cpp (+6-2) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp
index 53e26a9f8e229..c6d97ef4e971a 100644
--- a/clang/lib/Driver/ToolChains/Arch/X86.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp
@@ -132,10 +132,14 @@ void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
     if (StringRef(A->getValue()) == "native") {
       llvm::StringMap<bool> HostFeatures;
-      if (llvm::sys::getHostCPUFeatures(HostFeatures))
-        for (auto &F : HostFeatures)
+      if (llvm::sys::getHostCPUFeatures(HostFeatures)) {
+        for (auto &F : HostFeatures) {
+          if (!F.second && F.first() == "evex512")
+            continue;
           Features.push_back(
               Args.MakeArgString((F.second ? "+" : "-") + F.first()));
+        }
+      }
     }
   }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/91694