[clang] [clang][FMV] Pass the '+fmv' target-feature when FMV is enabled. (PR #87942)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-driver

Author: Alexandros Lamprineas (labrinea)

<details>
<summary>Changes</summary>

This will allow the backend to enable the corresponding subtarget feature (FeatureFMV), which in turn can be queried for llvm codegen decisions. See #<!-- -->87939 for example.

---
Full diff: https://github.com/llvm/llvm-project/pull/87942.diff


2 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+7-6) 
- (modified) clang/test/Driver/aarch64-features.c (+1) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 766a9b91e3c0ad..13dbd8ab261d3d 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7815,13 +7815,14 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   addOutlineAtomicsArgs(D, getToolChain(), Args, CmdArgs, Triple);
 
-  if (Triple.isAArch64() &&
-      (Args.hasArg(options::OPT_mno_fmv) ||
-       (Triple.isAndroid() && Triple.isAndroidVersionLT(23)) ||
-       getToolChain().GetRuntimeLibType(Args) != ToolChain::RLT_CompilerRT)) {
-    // Disable Function Multiversioning on AArch64 target.
+  if (Triple.isAArch64()) {
     CmdArgs.push_back("-target-feature");
-    CmdArgs.push_back("-fmv");
+    if (Args.hasArg(options::OPT_mno_fmv) ||
+        (Triple.isAndroid() && Triple.isAndroidVersionLT(23)) ||
+        getToolChain().GetRuntimeLibType(Args) != ToolChain::RLT_CompilerRT)
+      CmdArgs.push_back("-fmv");
+    else
+      CmdArgs.push_back("+fmv");
   }
 
   if (Args.hasFlag(options::OPT_faddrsig, options::OPT_fno_addrsig,
diff --git a/clang/test/Driver/aarch64-features.c b/clang/test/Driver/aarch64-features.c
index d2075c91314a8b..4f401ea65232f2 100644
--- a/clang/test/Driver/aarch64-features.c
+++ b/clang/test/Driver/aarch64-features.c
@@ -24,6 +24,7 @@
 
 // CHECK-FMV-OFF: "-target-feature" "-fmv"
 // CHECK-FMV-NOT: "-target-feature" "-fmv"
+// CHECK-FMV:     "-target-feature" "+fmv"
 
 // Check for AArch64 out-of-line atomics default settings.
 // RUN: %clang --target=aarch64-linux-android -rtlib=compiler-rt \

``````````

</details>


https://github.com/llvm/llvm-project/pull/87942