[clang] [llvm] [HLSL][SPIRV][DXIL] Implement `dot4add_i8packed` intrinsic (PR #113623)

[Steven Perron via cfe-commits]

================
@@ -1694,6 +1701,112 @@ bool SPIRVInstructionSelector::selectIntegerDot(Register ResVReg,
   return Result;
 }
 
+template <bool Signed>
+bool SPIRVInstructionSelector::selectDot4AddPacked(Register ResVReg,
+                                                   const SPIRVType *ResType,
+                                                   MachineInstr &I) const {
+  assert(I.getNumOperands() == 5);
+  assert(I.getOperand(2).isReg());
+  assert(I.getOperand(3).isReg());
+  assert(I.getOperand(4).isReg());
+  MachineBasicBlock &BB = *I.getParent();
+
+  auto DotOp = Signed ? SPIRV::OpSDot : SPIRV::OpUDot;
+  Register Dot = MRI->createVirtualRegister(&SPIRV::IDRegClass);
----------------
s-perron wrote:

That is good to know. I had not learned about the different register classes yet. Thanks for catching that.

https://github.com/llvm/llvm-project/pull/113623