Fix operator signedness mismatch issue

This helps to address issue shader-slang#5606.

source/slang/slang-ir-wgsl-legalize.cpp

@@ -1491,6 +1491,29 @@ struct LegalizeWGSLEntryPointContext
                 inst->getOperand(0));
             builder.replaceOperand(inst->getOperands(), newLhs);
         }
+        else if (
+             isIntegralType(inst->getOperand(0)->getDataType()) &&
+             isIntegralType(inst->getOperand(1)->getDataType()))
+        {
+            // If integer operands differ in signedness, convert the signed one to unsigned.
+            // We're assuming that the cases where this is bad have already been caught by
+            // common validation checks.
+            IntInfo opIntInfo[2] = {
+                getIntTypeInfo(inst->getOperand(0)->getDataType()),
+                getIntTypeInfo(inst->getOperand(1)->getDataType())
+            };
+            if (opIntInfo[0].isSigned != opIntInfo[1].isSigned)
+            {
+                int signedOpIndex = (int)opIntInfo[1].isSigned;
+                opIntInfo[signedOpIndex].isSigned = false;
+                IRBuilder builder(inst);
+                builder.setInsertBefore(inst);
+                auto newOp = builder.emitCast(
+                    builder.getType(getIntTypeOpFromInfo(opIntInfo[signedOpIndex])),
+                    inst->getOperand(signedOpIndex));
+                builder.replaceOperand(inst->getOperands() + signedOpIndex, newOp);
+            }
+        }
     }
 
     void processInst(IRInst* inst)