[llvm] [SPIR-V] Implement OpSpecConstantOp with ptr-cast operation (PR #109979)

[Nathan Gauër via llvm-commits]

================
@@ -1242,6 +1251,58 @@ static bool isUSMStorageClass(SPIRV::StorageClass::StorageClass SC) {
   }
 }
 
+// Returns true ResVReg is referred only from global vars and OpName's.
+static bool isASCastInGVar(MachineRegisterInfo *MRI, Register ResVReg) {
+  bool IsGRef = false;
+  bool IsAllowedRefs =
+      std::all_of(MRI->use_instr_begin(ResVReg), MRI->use_instr_end(),
+                  [&IsGRef](auto const &It) {
+                    unsigned Opcode = It.getOpcode();
+                    if (Opcode == SPIRV::OpConstantComposite ||
+                        Opcode == SPIRV::OpVariable ||
+                        isSpvIntrinsic(It, Intrinsic::spv_init_global))
+                      return IsGRef = true;
+                    return Opcode == SPIRV::OpName;
+                  });
+  return IsAllowedRefs && IsGRef;
+}
+
+Register SPIRVInstructionSelector::getUcharPtrTypeReg(
+    MachineInstr &I, SPIRV::StorageClass::StorageClass SC) const {
+  return GR.getSPIRVTypeID(GR.getOrCreateSPIRVPointerType(
+      GR.getOrCreateSPIRVIntegerType(8, I, TII), I, TII, SC));
+}
+
+MachineInstrBuilder
+SPIRVInstructionSelector::buildSpecConstantOp(MachineInstr &I, Register Dest,
+                                              Register Src, Register DestType,
+                                              uint32_t Opcode) const {
+  return BuildMI(*I.getParent(), I, I.getDebugLoc(),
+                 TII.get(SPIRV::OpSpecConstantOp))
+      .addDef(Dest)
+      .addUse(DestType)
+      .addImm(Opcode)
+      .addUse(Src);
----------------
Keenuts wrote:

Oh perfect, thanks!

https://github.com/llvm/llvm-project/pull/109979