[mlir][spirv] Check output of getConstantInt (#140568)

This patch adds an assert to check if the result of `getConstantInt` is
non-null. Previously the code failed with Segmentation Fault if
`getConstantInt` failed to look up the value. This primarily occurrs when
the value is defined as OpSpecConstant rather than OpConstant.

Author: IgWod-IMG

mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp

@@ -1062,12 +1062,30 @@ LogicalResult spirv::Deserializer::processCooperativeMatrixTypeKHR(
            << operands[2];
   }
 
-  unsigned rows = getConstantInt(operands[3]).getInt();
-  unsigned columns = getConstantInt(operands[4]).getInt();
+  IntegerAttr rowsAttr = getConstantInt(operands[3]);
+  IntegerAttr columnsAttr = getConstantInt(operands[4]);
+  IntegerAttr useAttr = getConstantInt(operands[5]);
+
+  if (!rowsAttr)
+    return emitError(unknownLoc, "OpTypeCooperativeMatrixKHR `Rows` references "
+                                 "undefined constant <id> ")
+           << operands[3];
+
+  if (!columnsAttr)
+    return emitError(unknownLoc, "OpTypeCooperativeMatrixKHR `Columns` "
+                                 "references undefined constant <id> ")
+           << operands[4];
+
+  if (!useAttr)
+    return emitError(unknownLoc, "OpTypeCooperativeMatrixKHR `Use` references "
+                                 "undefined constant <id> ")
+           << operands[5];
+
+  unsigned rows = rowsAttr.getInt();
+  unsigned columns = columnsAttr.getInt();
 
   std::optional<spirv::CooperativeMatrixUseKHR> use =
-      spirv::symbolizeCooperativeMatrixUseKHR(
-          getConstantInt(operands[5]).getInt());
+      spirv::symbolizeCooperativeMatrixUseKHR(useAttr.getInt());
   if (!use) {
     return emitError(
                unknownLoc,