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

[Steven Perron via cfe-commits]

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@@ -1694,6 +1701,110 @@ 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();
+
+  Register Dot = MRI->createVirtualRegister(&SPIRV::IDRegClass);
+  bool Result = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpDot))
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s-perron wrote:

You want to use the [OpSDot](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpSDot) and [OpUDot](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpUDot) instructions. If I said OpDot before that was a mistake on my part.

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