[clang] [PowerPC] Align bcdsetsign Sema validation with other BCD builtins (PR #178121)

[Tony Varghese via cfe-commits]

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@@ -147,7 +147,14 @@ bool SemaPPC::CheckPPCBuiltinFunctionCall(const TargetInfo &TI,
   switch (BuiltinID) {
   default:
     return false;
-  case PPC::BI__builtin_ppc_bcdsetsign:
+  case PPC::BI__builtin_ppc_bcdsetsign: {
+    // Arg0 must be vector unsigned char
+    if (!IsTypeVecUChar(TheCall->getArg(0)->getType(), 0))
+      return false;
+
+    // Restrict Arg1 constant range (0–1)
+    return SemaRef.BuiltinConstantArgRange(TheCall, 1, 0, 1);
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tonykuttai wrote:

I understand that we need validation since we are using `t` attribute for `TARGET_BUILTIN`. We should also be checking the second arg (`unsigned char`) as well right, not just the range of values it can take? 
Basically we need type validation for both arguments as well as range validation for the second argument.

https://github.com/llvm/llvm-project/pull/178121