[llvm] [SPIR-V] Insert a bitcast before load/store instruction to keep SPIR-V code valid (PR #84069)

[Vyacheslav Levytskyy via llvm-commits]

================
@@ -74,3 +81,74 @@ bool SPIRVTargetLowering::getTgtMemIntrinsic(IntrinsicInfo &Info,
   }
   return false;
 }
+
+// Insert a bitcast before the instruction to keep SPIR-V code valid
+// when there is a type mismatch between results and operand types.
+static void validatePtrTypes(const SPIRVSubtarget &STI,
+                             MachineRegisterInfo *MRI, SPIRVGlobalRegistry &GR,
+                             MachineInstr &I, SPIRVType *ResType,
+                             unsigned OpIdx) {
+  Register OpReg = I.getOperand(OpIdx).getReg();
+  SPIRVType *TypeInst = MRI->getVRegDef(OpReg);
+  SPIRVType *OpType = GR.getSPIRVTypeForVReg(
+      TypeInst && TypeInst->getOpcode() == SPIRV::OpFunctionParameter
+          ? TypeInst->getOperand(1).getReg()
+          : OpReg);
+  if (!ResType || !OpType || OpType->getOpcode() != SPIRV::OpTypePointer)
+    return;
+  SPIRVType *ElemType = GR.getSPIRVTypeForVReg(OpType->getOperand(2).getReg());
+  if (!ElemType || ElemType == ResType)
+    return;
+  // There is a type mismatch between results and operand types
+  // and we insert a bitcast before the instruction to keep SPIR-V code valid
----------------
VyacheslavLevytskyy wrote:

Yes, indeed, I've seen that the logic is spread over several passes. However, I doubt that there exists both clear and gradual solution that is able to address existing type inference problems. We may see this commit as a step towards consolidation of those layers into a consistently organized approach. The plan is to start with adding this validation layer at the exit, to be sure that the primary goal of emitting SPIRV preserves and other tools may work with SPIRV Backend's output. To address type inference in general and ensure its correctness in earlier passes is quite another problem that is planned to be addressed quite soon as well.

https://github.com/llvm/llvm-project/pull/84069