Refactor ROM method info caching to separate ROMMethod and BytecodePC handling

Author: Harshitha Popuri

runtime/oti/stackmap_api.h

@@ -207,14 +207,21 @@ void
 initializeBasicROMMethodInfo(J9StackWalkState *walkState, J9ROMMethod *romMethod);
 
 /**
- * Populate ROM method info, including argbits, stackmap, and localmap.
- *
- * @param walkState current stack walk state
- * @param romMethod ROM method pointer
- * @param key identifying key (method address for method-case, PC for PC-case)
+ * @brief
+ * @param walkState
+ * @param romMethod
+ */
+void
+getROMMethodInfoForROMMethod(J9StackWalkState *walkState, J9ROMMethod *romMethod);
+
+/**
+ * @brief
+ * @param walkState
+ * @param romMethod
+ * @param pc
  */
 void
-populateROMMethodInfo(J9StackWalkState *walkState, J9ROMMethod *romMethod, void *key);
+getROMMethodInfoForBytecodePC(J9StackWalkState *walkState, J9ROMMethod *romMethod, UDATA pc);
 
 #ifdef __cplusplus
 }

runtime/stackmap/mapcache.cpp

@@ -72,7 +72,7 @@ checkROMMethodInfoCache(J9ClassLoader *classLoader, void *key, J9ROMMethodInfo *
 			exemplar.key = key;
 			J9ROMMethodInfo *entry = (J9ROMMethodInfo *)hashTableFind(cache, &exemplar);
 			if (NULL != entry) {
-				*outInfo = *entry; /* Copy struct */
+				*outInfo = *entry;
 				found = true;
 			}
 		}
@@ -95,18 +95,19 @@ updateROMMethodInfoCache(J9JavaVM *vm, J9ClassLoader *classLoader, J9ROMMethodIn
 
 	J9HashTable *cache = classLoader->romMethodInfoCache;
 	if (NULL == cache) {
+		/* Create the cache if it doesn't exist */
 		cache = hashTableNew(
-			OMRPORT_FROM_J9PORT(vm->portLibrary),
-			J9_GET_CALLSITE(),
-			0,
-			sizeof(J9ROMMethodInfo),
-			sizeof(J9ROMMethodInfo *),
-			0,
-			J9MEM_CATEGORY_VM,
-			romMethodInfoHashFn,
-			romMethodInfoEqualFn,
-			NULL,
-			NULL);
+				OMRPORT_FROM_J9PORT(vm->portLibrary),
+				J9_GET_CALLSITE(),
+				0,
+				sizeof(J9ROMMethodInfo),
+				sizeof(J9ROMMethodInfo *),
+				0,
+				J9MEM_CATEGORY_VM,
+				romMethodInfoHashFn,
+				romMethodInfoEqualFn,
+				NULL,
+				NULL);
 		classLoader->romMethodInfoCache = cache;
 	}
 
@@ -117,69 +118,100 @@ updateROMMethodInfoCache(J9JavaVM *vm, J9ClassLoader *classLoader, J9ROMMethodIn
 	omrthread_monitor_exit(mapCacheMutex);
 }
 
-void
-populateROMMethodInfo(J9StackWalkState *walkState, J9ROMMethod *romMethod, void *key)
+static void
+populateROMMethodInfo(J9StackWalkState *walkState, J9ROMMethod *romMethod, void *key, UDATA pc, bool computeStackAndLocals)
 {
-	initializeBasicROMMethodInfo(walkState, romMethod);
-
 	J9Method *method = walkState->method;
 	J9ClassLoader *classLoader = J9_CLASS_FROM_METHOD(method)->classLoader;
 	J9JavaVM *vm = walkState->javaVM;
 
-	UDATA codeSize = (UDATA)J9_BYTECODE_SIZE_FROM_ROM_METHOD(romMethod);
-	void *bytecodeStart = (void*)J9_BYTECODE_START_FROM_ROM_METHOD(romMethod);
-
-	bool isMethodCase = (key == (void *)romMethod);
-	UDATA pc = 0;
-
-	if (!isMethodCase) {
-		// Compute PC only if key points into bytecode range
-		if ((uintptr_t)key >= (uintptr_t)bytecodeStart &&
-			(uintptr_t)key < (uintptr_t)bytecodeStart + codeSize) {
-			pc = (UDATA)((uintptr_t)key - (uintptr_t)bytecodeStart);
-		}
-	}
-
-	J9ROMClass *romClass = J9_CLASS_FROM_METHOD(method)->romClass;
 	J9ROMMethodInfo newInfo = {0};
 	newInfo.key = key;
+	J9ROMClass *romClass = J9_CLASS_FROM_METHOD(method)->romClass;
 
-	// Always compute argbits
+	/* Always compute argument bits */
 	j9localmap_ArgBitsForPC0(romClass, romMethod, newInfo.argbits);
 
-	if (!isMethodCase && pc < codeSize) {
-		// Stack map
+	if (computeStackAndLocals && pc < (UDATA)J9_BYTECODE_SIZE_FROM_ROM_METHOD(romMethod)) {
+		/* Compute stack map for this PC */
 		j9stackmap_StackBitsForPC(
-			vm->portLibrary,
-			pc,
-			romClass,
-			romMethod,
-			newInfo.stackmap,
-			J9_STACKMAP_CACHE_SLOTS << 5,
-			NULL, NULL, NULL);
-
-		// Local map
+				vm->portLibrary,
+				pc,
+				romClass,
+				romMethod,
+				newInfo.stackmap,
+				J9_STACKMAP_CACHE_SLOTS << 5,
+				NULL,
+				NULL,
+				NULL);
+
+		/* Compute local variable map for this PC */
 		vm->localMapFunction(
-			vm->portLibrary,
-			romClass,
-			romMethod,
-			pc,
-			newInfo.localmap,
-			NULL, NULL, NULL);
+				vm->portLibrary,
+				romClass,
+				romMethod,
+				pc,
+				newInfo.localmap,
+				NULL,
+				NULL,
+				NULL);
 	}
 
-	// Copy metadata
+	/* Copy metadata */
 	newInfo.modifiers = romMethod->modifiers;
 	newInfo.argCount = J9_ARG_COUNT_FROM_ROM_METHOD(romMethod);
 	newInfo.tempCount = J9_TEMP_COUNT_FROM_ROM_METHOD(romMethod);
 
-	// Insert into cache
+	/* Insert into cache */
 	updateROMMethodInfoCache(vm, classLoader, &newInfo);
 
-	// Reflect it into the current walkState
+	/* Reflect into current walkState */
 	walkState->romMethodInfo = newInfo;
 }
 
+void
+getROMMethodInfoForROMMethod(J9StackWalkState *walkState, J9ROMMethod *romMethod)
+{
+	initializeBasicROMMethodInfo(walkState, romMethod);
+	J9Method *method = walkState->method;
+	J9ClassLoader *classLoader = J9_CLASS_FROM_METHOD(method)->classLoader;
+
+	void *key = (void *)romMethod;
+	J9ROMMethodInfo tmp = {0};
+
+	/* Check cache first */
+	if (!checkROMMethodInfoCache(classLoader, key, &tmp)) {
+		/* Cache miss or not populated: populate argbits only */
+		populateROMMethodInfo(walkState, romMethod, key, 0, false);
+	} else {
+		walkState->romMethodInfo = tmp;
+	}
+}
+
+/* Bytecode PC: compute argbits + stackmap + localmap */
+void
+getROMMethodInfoForBytecodePC(J9StackWalkState *walkState, J9ROMMethod *romMethod, UDATA pc)
+{
+	initializeBasicROMMethodInfo(walkState, romMethod);
+	if (pc <= J9SF_MAX_SPECIAL_FRAME_TYPE || pc >= (UDATA)J9_BYTECODE_SIZE_FROM_ROM_METHOD(romMethod)) {
+		return;
+	}
+
+	J9Method *method = walkState->method;
+	J9ClassLoader *classLoader = J9_CLASS_FROM_METHOD(method)->classLoader;
+
+	void *key = (void *)( (uintptr_t)J9_BYTECODE_START_FROM_ROM_METHOD(romMethod) + (uintptr_t)pc );
+	J9ROMMethodInfo tmp = {0};
+
+	/* Check cache first */
+	if (!checkROMMethodInfoCache(classLoader, key, &tmp)) {
+		/* Cache miss or not populated: compute stack/local maps */
+		populateROMMethodInfo(walkState, romMethod, key, pc, true);
+	} else {
+		walkState->romMethodInfo = tmp;
+	}
+}
+
 #if 0
 
 void

runtime/vm/swalk.c

@@ -761,7 +761,7 @@ walkMethodFrame(J9StackWalkState * walkState)
 		J9ROMMethodInfo *romMethodInfo = &walkState->romMethodInfo;
 
 		//initializeBasicROMMethodInfo(walkState, romMethod);
-		populateROMMethodInfo(walkState, romMethod, walkState->pc);
+		getROMMethodInfoForROMMethod(walkState, romMethod);
 
 		walkState->constantPool = UNTAGGED_METHOD_CP(walkState->method);
 		walkState->argCount = romMethodInfo->argCount;
@@ -1027,8 +1027,8 @@ walkBytecodeFrame(J9StackWalkState * walkState)
 		J9ROMMethodInfo *romMethodInfo = &walkState->romMethodInfo;
 
 		//initializeBasicROMMethodInfo(walkState, romMethod);
-		populateROMMethodInfo(walkState, romMethod, walkState->pc);
-
+		UDATA pcOffset = walkState->pc - J9_BYTECODE_START_FROM_RAM_METHOD(walkState->method);
+		getROMMethodInfoForBytecodePC(walkState, romMethod, pcOffset);
 		walkState->constantPool = UNTAGGED_METHOD_CP(walkState->method);
 
 #if defined(J9VM_OPT_METHOD_HANDLE)