[mlir][spirv] Avoid repeated hash lookups (NFC) (#111619)

Author: kazutakahirata

mlir/lib/Dialect/SPIRV/IR/SPIRVOps.cpp

@@ -1538,11 +1538,8 @@ LogicalResult spirv::ModuleOp::verifyRegions() {
 
       auto key = std::pair<spirv::FuncOp, spirv::ExecutionModel>(
           funcOp, entryPointOp.getExecutionModel());
-      auto entryPtIt = entryPoints.find(key);
-      if (entryPtIt != entryPoints.end()) {
+      if (!entryPoints.try_emplace(key, entryPointOp).second)
         return entryPointOp.emitError("duplicate of a previous EntryPointOp");
-      }
-      entryPoints[key] = entryPointOp;
     } else if (auto funcOp = dyn_cast<spirv::FuncOp>(op)) {
       // If the function is external and does not have 'Import'
       // linkage_attributes(LinkageAttributes), throw an error. 'Import'