[SPIRV][HLSL] Add mad intrinsic lowering for spirv (#89130)

- `clang/lib/CodeGen/CGBuiltin.cpp` - Add a generic mull add
implementation. Make DXIL implementation tied to target.

resolves #88944

Author: farzonl

clang/lib/CodeGen/CGBuiltin.cpp

@@ -18296,20 +18296,28 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
     Value *M = EmitScalarExpr(E->getArg(0));
     Value *A = EmitScalarExpr(E->getArg(1));
     Value *B = EmitScalarExpr(E->getArg(2));
-    if (E->getArg(0)->getType()->hasFloatingRepresentation()) {
+    if (E->getArg(0)->getType()->hasFloatingRepresentation())
       return Builder.CreateIntrinsic(
           /*ReturnType*/ M->getType(), Intrinsic::fmuladd,
-          ArrayRef<Value *>{M, A, B}, nullptr, "dx.fmad");
-    }
+          ArrayRef<Value *>{M, A, B}, nullptr, "hlsl.fmad");
+
     if (E->getArg(0)->getType()->hasSignedIntegerRepresentation()) {
-      return Builder.CreateIntrinsic(
-          /*ReturnType*/ M->getType(), Intrinsic::dx_imad,
-          ArrayRef<Value *>{M, A, B}, nullptr, "dx.imad");
+      if (CGM.getTarget().getTriple().getArch() == llvm::Triple::dxil)
+        return Builder.CreateIntrinsic(
+            /*ReturnType*/ M->getType(), Intrinsic::dx_imad,
+            ArrayRef<Value *>{M, A, B}, nullptr, "dx.imad");
+
+      Value *Mul = Builder.CreateNSWMul(M, A);
+      return Builder.CreateNSWAdd(Mul, B);
     }
     assert(E->getArg(0)->getType()->hasUnsignedIntegerRepresentation());
-    return Builder.CreateIntrinsic(
-        /*ReturnType=*/M->getType(), Intrinsic::dx_umad,
-        ArrayRef<Value *>{M, A, B}, nullptr, "dx.umad");
+    if (CGM.getTarget().getTriple().getArch() == llvm::Triple::dxil)
+      return Builder.CreateIntrinsic(
+          /*ReturnType=*/M->getType(), Intrinsic::dx_umad,
+          ArrayRef<Value *>{M, A, B}, nullptr, "dx.umad");
+
+    Value *Mul = Builder.CreateNUWMul(M, A);
+    return Builder.CreateNUWAdd(Mul, B);
   }
   case Builtin::BI__builtin_hlsl_elementwise_rcp: {
     Value *Op0 = EmitScalarExpr(E->getArg(0));