[Clang][RISCV] Guard vector float16 type correctly with semantic analysis

Before this commit, vector float 16 types (e.g. `vfloat16m1_t`) of RVV
is only defined when extension `zvfh` is defined. However this
generate inaccurate diagnostics like:

```
error: unknown type name 'vfloat16m1_t'
```

This commit improves the compiler by guarding type check correctly
under semantic analysis.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D143657

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index f983c47..fd41276 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2039,6 +2039,12 @@ void Sema::checkTypeSupport(QualType Ty, SourceLocation Loc, ValueDecl *D) {
         targetDiag(D->getLocation(), diag::note_defined_here, FD) << D;
     }
 
+    if (Ty->isRVVType(/* Bitwidth */ 16, /* IsFloat */ true) &&
+        !Context.getTargetInfo().hasFeature("experimental-zvfh")) {
+      Diag(Loc, diag::err_riscv_type_requires_extension, FD)
+          << Ty << "zvfh";
+    }
+
     // Don't allow SVE types in functions without a SVE target.
     if (Ty->isSVESizelessBuiltinType() && FD && FD->hasBody()) {
       llvm::StringMap<bool> CallerFeatureMap;