[clang] [llvm] [NFC][clang][FMV][TargetInfo] Refactor API for FMV feature priority. (PR #116257)

[Alexandros Lamprineas via cfe-commits]

================
@@ -4216,22 +4216,11 @@ static void ReplaceUsesOfNonProtoTypeWithRealFunction(llvm::GlobalValue *Old,
                                                       llvm::Function *NewFn);
 
 static unsigned
-TargetMVPriority(const TargetInfo &TI,
-                 const CodeGenFunction::MultiVersionResolverOption &RO) {
-  unsigned Priority = 0;
-  unsigned NumFeatures = 0;
-  for (StringRef Feat : RO.Conditions.Features) {
-    Priority = std::max(Priority, TI.multiVersionSortPriority(Feat));
-    NumFeatures++;
-  }
-
-  if (!RO.Conditions.Architecture.empty())
-    Priority = std::max(
-        Priority, TI.multiVersionSortPriority(RO.Conditions.Architecture));
-
-  Priority += TI.multiVersionFeatureCost() * NumFeatures;
-
-  return Priority;
+getFMVPriority(const TargetInfo &TI,
+               const CodeGenFunction::MultiVersionResolverOption &RO) {
+  llvm::SmallVector<StringRef, 8> Features{RO.Conditions.Features};
+  Features.push_back(RO.Conditions.Architecture);
+  return TI.getFMVPriority(Features);
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labrinea wrote:

> RO.Conditions.Architecture isn't suitable for AArch64, and correct me if I am wrong but so far it doesn't seem that risc-v is using it either?

Ok, looking at `clang/test/CodeGen/attr-target-version-riscv.c` I can see that riscv does support `arch` but line https://github.com/llvm/llvm-project/blob/main/clang/lib/CodeGen/CodeGenModule.cpp#L4297 suggests that RO.Conditions.Architecture is empty for the riscv target? That seems odd.

I guess this arrises from the fact that on AArch64 and x86, features are split by '+' whereas on riscv they split by ';'. The argument `ArrayRef<StringRef>` I am using suggests that the attribute string has been parsed for the other targets, which isn't the case for riscv. That doesn't seem right either:
line https://github.com/llvm/llvm-project/blob/main/clang/lib/CodeGen/CodeGenModule.cpp#L4292 appends an unparsed string to a list of parsed features.

https://github.com/llvm/llvm-project/pull/116257