[clang] [llvm] [HLSL] Implementation of dot intrinsic (PR #81190)

[Chris B via llvm-commits]

================
@@ -17959,6 +17964,54 @@ llvm::Value *CodeGenFunction::EmitScalarOrConstFoldImmArg(unsigned ICEArguments,
   return Arg;
 }
 
+Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
+                                            const CallExpr *E) {
+  if (!getLangOpts().HLSL)
+    return nullptr;
+
+  switch (BuiltinID) {
+  case Builtin::BI__builtin_hlsl_dot: {
+    Value *Op0 = EmitScalarExpr(E->getArg(0));
+    Value *Op1 = EmitScalarExpr(E->getArg(1));
+    llvm::Type *T0 = Op0->getType();
+    llvm::Type *T1 = Op1->getType();
+    if (!T0->isVectorTy() && !T1->isVectorTy()) {
+      if (T0->isFloatingPointTy()) {
+        return Builder.CreateFMul(Op0, Op1, "dx.dot");
+      }
+
+      if (T0->isIntegerTy()) {
+        return Builder.CreateMul(Op0, Op1, "dx.dot");
+      }
+      // Bools should have been promoted
+      assert(
+          false &&
+          "Dot product on a scalar is only supported on integers and floats.");
----------------
llvm-beanz wrote:

Generally `assert(false)` should be unreachable.
```suggestion
          llvm_unreachable("Scalar dot product is only supported on ints and floats.");
```

https://github.com/llvm/llvm-project/pull/81190