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

[Phoebe Wang via cfe-commits]

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

>From 6ea15aa0ee6726cad8dccff10155f058afa0f013 Mon Sep 17 00:00:00 2001
From: Phoebe Wang <phoebe.wang at intel.com>
Date: Fri, 10 May 2024 11:21:41 +0800
Subject: [PATCH 1/2] [X86][Driver] Do not add `-evex512` for `-march=native`
 when the target doesn't support AVX512

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

Fixes: #91076
---
 clang/lib/Driver/ToolChains/Arch/X86.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

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()));
+        }
+      }
     }
   }
 

>From d50ae3b317839f5603b091aa029414b3c3c42259 Mon Sep 17 00:00:00 2001
From: Phoebe Wang <phoebe.wang at intel.com>
Date: Fri, 10 May 2024 12:02:09 +0800
Subject: [PATCH 2/2] Address review comment

---
 clang/lib/Driver/ToolChains/Arch/X86.cpp | 8 ++------
 llvm/lib/TargetParser/Host.cpp           | 3 ++-
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp
index c6d97ef4e971a..53e26a9f8e229 100644
--- a/clang/lib/Driver/ToolChains/Arch/X86.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp
@@ -132,14 +132,10 @@ 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 (!F.second && F.first() == "evex512")
-            continue;
+      if (llvm::sys::getHostCPUFeatures(HostFeatures))
+        for (auto &F : HostFeatures)
           Features.push_back(
               Args.MakeArgString((F.second ? "+" : "-") + F.first()));
-        }
-      }
     }
   }
 
diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
index 834f4536f93ac..c5156c6cb802c 100644
--- a/llvm/lib/TargetParser/Host.cpp
+++ b/llvm/lib/TargetParser/Host.cpp
@@ -1802,7 +1802,8 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
   Features["rtm"]        = HasLeaf7 && ((EBX >> 11) & 1);
   // AVX512 is only supported if the OS supports the context save for it.
   Features["avx512f"]    = HasLeaf7 && ((EBX >> 16) & 1) && HasAVX512Save;
-  Features["evex512"]    = Features["avx512f"];
+  if (Features["avx512f"])
+    Features["evex512"]  = true;
   Features["avx512dq"]   = HasLeaf7 && ((EBX >> 17) & 1) && HasAVX512Save;
   Features["rdseed"]     = HasLeaf7 && ((EBX >> 18) & 1);
   Features["adx"]        = HasLeaf7 && ((EBX >> 19) & 1);