Fix handling of FP-classify where the last arg fails to convert

The last argument of an FP-classify function was checked for vailidity
as an expression, but we never ensured that the usual unary
conversions/etc properly resulted in a valid value. Thus, when we got
the value, it was null, so we had a null dereference.

This patch instead fails out/marks the function call as invalid if the
argument is incorrect.  I DID consider just allowing it to continue, but
the result was an extraneous error about how the last argument wasn't a
float (in this case, it was an overload set).

Fixes: #107411

Author: erichkeane

clang/lib/Sema/SemaChecking.cpp

@@ -4936,10 +4936,19 @@ bool Sema::BuiltinFPClassification(CallExpr *TheCall, unsigned NumArgs,
   // Usual Unary Conversions will convert half to float, which we want for
   // machines that use fp16 conversion intrinsics. Else, we wnat to leave the
   // type how it is, but do normal L->Rvalue conversions.
-  if (Context.getTargetInfo().useFP16ConversionIntrinsics())
-    OrigArg = UsualUnaryConversions(OrigArg).get();
-  else
-    OrigArg = DefaultFunctionArrayLvalueConversion(OrigArg).get();
+  if (Context.getTargetInfo().useFP16ConversionIntrinsics()) {
+    ExprResult Res = UsualUnaryConversions(OrigArg);
+
+    if (!Res.isUsable())
+      return true;
+    OrigArg = Res.get();
+  } else {
+    ExprResult Res = DefaultFunctionArrayLvalueConversion(OrigArg);
+
+    if (!Res.isUsable())
+      return true;
+    OrigArg = Res.get();
+  }
   TheCall->setArg(FPArgNo, OrigArg);
 
   QualType VectorResultTy;

clang/test/Sema/builtin-unary-fp.c

@@ -14,4 +14,8 @@ void a(void) {
   check(__builtin_fpclassify(0, 1, 2, 3, 4.5, 5.0)); // expected-warning{{implicit conversion from 'double' to 'int' changes value from 4.5 to 4}}
   check(__builtin_fpclassify(0, 0, 0, 0, 1)); // expected-error{{too few arguments}}
   check(__builtin_fpclassify(0, 0, 0, 0, 0, 1, 0)); // expected-error{{too many arguments}}
+
+  check(__builtin_fpclassify(0,0,0,0,0, (invalid))); // expected-error{{use of undeclared identifier 'invalid'}}
+  check(__builtin_fpclassify(0,0,0,0,0, (inf))); // expected-error{{use of undeclared identifier 'inf'}}
+                                                // expected-error@-1{{reference to overloaded function could not be resolved}}
 }