[clang] [llvm] [HLSL][DXIL][SPIRV] Create llvm dot intrinsic and use for HLSL (PR #102872)

[Thorsten Schütt via cfe-commits]

================
@@ -1088,6 +1088,27 @@ def G_FNEARBYINT : GenericInstruction {
   let hasSideEffects = false;
 }
 
+/// Floating point vector dot product
+def G_FDOTPROD : GenericInstruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins type0:$src1, type0:$src2);
+  let hasSideEffects = false;
----------------
tschuett wrote:

dot products take two vectors and return a scalar.
```
f G_FDOTPROD : GenericInstruction {
  let OutOperandList = (outs type0:$dst);
  let InOperandList = (ins type1:$src1, type1:$src2);
  let hasSideEffects = false;
```
You have to change the sources to type1 and adapt your legalizer accordingly.

https://github.com/llvm/llvm-project/pull/102872