[Clang] Permit half precision in __builtin_complex (#156479)

Summary:
This was forbidden previously, which made us divergent with the GCC
implementation. Permit this by simply removing this Sema check.

Fixes: #156463

Author: jhuber6

clang/lib/Sema/SemaChecking.cpp

@@ -5551,16 +5551,6 @@ bool Sema::BuiltinComplex(CallExpr *TheCall) {
            << Real->getSourceRange() << Imag->getSourceRange();
   }
 
-  // We don't allow _Complex _Float16 nor _Complex __fp16 as type specifiers;
-  // don't allow this builtin to form those types either.
-  // FIXME: Should we allow these types?
-  if (Real->getType()->isFloat16Type())
-    return Diag(TheCall->getBeginLoc(), diag::err_invalid_complex_spec)
-           << "_Float16";
-  if (Real->getType()->isHalfType())
-    return Diag(TheCall->getBeginLoc(), diag::err_invalid_complex_spec)
-           << "half";
-
   TheCall->setType(Context.getComplexType(Real->getType()));
   return false;
 }

clang/test/CodeGen/complex_Float16.c

@@ -0,0 +1,22 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm %s -o - | FileCheck %s
+
+// CHECK-LABEL: define dso_local <2 x half> @builtin_complex(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[RETVAL:%.*]] = alloca { half, half }, align 2
+// CHECK-NEXT:    [[A:%.*]] = alloca half, align 2
+// CHECK-NEXT:    store half 0xH0000, ptr [[A]], align 2
+// CHECK-NEXT:    [[TMP0:%.*]] = load half, ptr [[A]], align 2
+// CHECK-NEXT:    [[TMP1:%.*]] = load half, ptr [[A]], align 2
+// CHECK-NEXT:    [[RETVAL_REALP:%.*]] = getelementptr inbounds nuw { half, half }, ptr [[RETVAL]], i32 0, i32 0
+// CHECK-NEXT:    [[RETVAL_IMAGP:%.*]] = getelementptr inbounds nuw { half, half }, ptr [[RETVAL]], i32 0, i32 1
+// CHECK-NEXT:    store half [[TMP0]], ptr [[RETVAL_REALP]], align 2
+// CHECK-NEXT:    store half [[TMP1]], ptr [[RETVAL_IMAGP]], align 2
+// CHECK-NEXT:    [[TMP2:%.*]] = load <2 x half>, ptr [[RETVAL]], align 2
+// CHECK-NEXT:    ret <2 x half> [[TMP2]]
+//
+_Complex _Float16 builtin_complex(void) {
+  _Float16 a = 0;
+  return __builtin_complex(a, a);
+}

clang/test/Sema/Float16.c

@@ -14,9 +14,10 @@
 _Float16 f;
 
 #ifdef HAVE
+// expected-no-diagnostics
 _Complex _Float16 a;
 void builtin_complex(void) {
   _Float16 a = 0;
-  (void)__builtin_complex(a, a); // expected-error {{'_Complex _Float16' is invalid}}
+  (void)__builtin_complex(a, a);
 }
 #endif

clang/test/Sema/fp16-sema.c

@@ -28,10 +28,3 @@ extern __fp16 *(*gf1) (void);
 
 typedef __fp16 (*tf1) (void); // expected-error {{function return value cannot have __fp16 type; did you forget * ?}}
 typedef __fp16 *(*tg1) (void);
-
-void testComplex() {
-  // FIXME: Should these be valid?
-  _Complex __fp16 a; // expected-error {{'_Complex half' is invalid}}
-  __fp16 b;
-  a = __builtin_complex(b, b); // expected-error {{'_Complex half' is invalid}}
-}

clang/test/Sema/riscv-fp16.c

@@ -29,10 +29,3 @@ extern __fp16 *(*gf1) (void);
 
 typedef __fp16 (*tf1) (void); // expected-error {{function return value cannot have __fp16 type; did you forget * ?}}
 typedef __fp16 *(*tg1) (void);
-
-void testComplex() {
-  // FIXME: Should these be valid?
-  _Complex __fp16 a; // expected-error {{'_Complex half' is invalid}}
-  __fp16 b;
-  a = __builtin_complex(b, b); // expected-error {{'_Complex half' is invalid}}
-}