[clang] [RISCV] Implement validateGlobalRegisterVariable. (PR #109596)

[Pengcheng Wang via cfe-commits]

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@@ -486,3 +486,15 @@ bool RISCVTargetInfo::validateCpuSupports(StringRef Feature) const {
 bool RISCVTargetInfo::isValidFeatureName(StringRef Name) const {
   return llvm::RISCVISAInfo::isSupportedExtensionFeature(Name);
 }
+
+bool RISCVTargetInfo::validateGlobalRegisterVariable(
+    StringRef RegName, unsigned RegSize, bool &HasSizeMismatch) const {
+  if (RegName == "ra" || RegName == "sp" || RegName == "gp" ||
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wangpc-pp wrote:

`zero` is not writable/allocatable?

https://github.com/llvm/llvm-project/pull/109596