add early failure if lerp arguments were type promoted to double

Author: farzonl

clang/lib/Sema/SemaChecking.cpp

@@ -5233,10 +5233,6 @@ bool CheckVectorElementCallArgs(Sema *S, CallExpr *TheCall) {
                            TheCall->getArg(1)->getEndLoc());
         retValue = true;
       }
-
-      if (!retValue)
-        TheCall->setType(VecTyA->getElementType());
-
       return retValue;
     }
   }
@@ -5254,7 +5250,11 @@ bool CheckAllArgsHaveFloatRepresentation(Sema *S, CallExpr *TheCall) {
   QualType ExpectedType = S->Context.FloatTy;
   for (unsigned i = 0; i < TheCall->getNumArgs(); ++i) {
     QualType PassedType = TheCall->getArg(i)->getType();
-    if (!PassedType->hasFloatingRepresentation()) {
+    ExpectedType = PassedType->isHalfType() && S->getLangOpts().NativeHalfType
+                       ? S->Context.HalfTy
+                       : S->Context.FloatTy;
+    if (PassedType == S->Context.DoubleTy ||
+        !PassedType->hasFloatingRepresentation()) {
       if (auto *VecTyA = PassedType->getAs<VectorType>())
         ExpectedType = S->Context.getVectorType(
             ExpectedType, VecTyA->getNumElements(), VecTyA->getVectorKind());
@@ -5300,6 +5300,8 @@ bool Sema::CheckHLSLBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
       return true;
     if (SemaBuiltinElementwiseTernaryMath(TheCall))
       return true;
+    if (CheckAllArgsHaveFloatRepresentation(this, TheCall))
+      return true;
     break;
   }
   case Builtin::BI__builtin_hlsl_mad: {

clang/test/CodeGenHLSL/builtins/lerp-builtin.hlsl

@@ -1,19 +1,4 @@
 // RUN: %clang_cc1 -finclude-default-header -x hlsl -triple dxil-pc-shadermodel6.3-library %s -fnative-half-type -emit-llvm -disable-llvm-passes -o - | FileCheck %s
-// XFAIL: *
-
-// CHECK-LABEL: builtin_lerp_half_scalar
-// CHECK: %dx.lerp = call half @llvm.dx.lerp.f16(half %{{.*}}, half %{{.*}}, half %{{.*}})
-// CHECK: ret half %dx.lerp
-half builtin_lerp_half_scalar (half p0) {
-  return __builtin_hlsl_lerp ( p0, p0, p0 );
-}
-
-// CHECK-LABEL: builtin_lerp_float_scalar
-// CHECK: %dx.lerp = call float @llvm.dx.lerp.f32(float %{{.*}}, float %{{.*}}, float %{{.*}})
-// CHECK: ret float %dx.lerp
-float builtin_lerp_float_scalar ( float p0) {
-  return __builtin_hlsl_lerp ( p0, p0, p0 );
-}
 
 // CHECK-LABEL: builtin_lerp_half_vector
 // CHECK: %dx.lerp = call <3 x half> @llvm.dx.lerp.v3f16(<3 x half> %0, <3 x half> %1, <3 x half> %2)

clang/test/SemaHLSL/BuiltIns/lerp-errors.hlsl

@@ -92,5 +92,18 @@ float builtin_lerp_int_to_float_promotion(float p0, int p1) {
 
 float4 test_lerp_int4(int4 p0, int4 p1, int4 p2) {
   return __builtin_hlsl_lerp(p0, p1, p2);
-   // expected-error@-1 {{1st argument must be a floating point type (was 'int4' (aka 'vector<int, 4>'))}}
-}
+  // expected-error@-1 {{1st argument must be a floating point type (was 'int4' (aka 'vector<int, 4>'))}}
+}
+
+// note: DefaultVariadicArgumentPromotion --> DefaultArgumentPromotion has already promoted to double
+// we don't know anymore that the input was half when __builtin_hlsl_lerp is called so we default to float
+// for expected type
+half builtin_lerp_half_scalar (half p0) {
+  return __builtin_hlsl_lerp ( p0, p0, p0 );
+  // expected-error@-1 {{passing 'double' to parameter of incompatible type 'float'}}
+}
+
+float builtin_lerp_float_scalar ( float p0) {
+  return __builtin_hlsl_lerp ( p0, p0, p0 );
+  // expected-error@-1 {{passing 'double' to parameter of incompatible type 'float'}}
+}