[clang] [llvm] [HLSL] Add wave prefix count bits function (PR #178059)

[Tex Riddell via llvm-commits]

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@@ -2715,6 +2718,56 @@ bool SPIRVInstructionSelector::selectWaveActiveCountBits(
   return Result;
 }
 
+bool SPIRVInstructionSelector::selectWavePrefixBitCount(
+    Register ResVReg, const SPIRVType *ResType, MachineInstr &I) const {
+
+  assert(I.getNumOperands() == 3);
+
+  auto Op = I.getOperand(2);
+  assert(Op.isReg());
+
+  MachineBasicBlock &BB = *I.getParent();
+  DebugLoc DL = I.getDebugLoc();
+
+  Register InputRegister = Op.getReg();
+  SPIRVType *InputType = GR.getSPIRVTypeForVReg(InputRegister);
+
+  if (!InputType)
+    report_fatal_error("Input Type could not be determined.");
+
+  if (!GR.isScalarOrVectorOfType(InputRegister, SPIRV::OpTypeBool))
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tex3d wrote:

Should this really support vector input, when the HLSL intrinsic and builtin does not?

https://github.com/llvm/llvm-project/pull/178059