Changeset 121480 in webkit for trunk/Source/JavaScriptCore/bytecode/CodeBlock.h

Timestamp:

Jun 28, 2012, 4:03:07 PM (13 years ago)

Author:

[email protected]

Message:

Adding a commenting utility to record BytecodeGenerator comments
with opcodes that are emitted. Presently, the comments can only
be constant strings. Adding comments for opcodes is optional.
If a comment is added, the comment will be printed following the
opcode when CodeBlock::dump() is called.

This utility is disabled by default, and is only meant for VM
development purposes. It should not be enabled for product builds.

To enable this utility, set ENABLE_BYTECODE_COMMENTS in CodeBlock.h
to 1.

​https://bugs.webkit.org/show_bug.cgi?id=90095

Patch by Mark Lam <​[email protected]> on 2012-06-28
Reviewed by Geoffrey Garen.

• GNUmakefile.list.am:
• JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore.vcproj:
• JavaScriptCore.xcodeproj/project.pbxproj:
• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::dumpBytecodeCommentAndNewLine): Dumps the comment.
(JSC):
(JSC::CodeBlock::printUnaryOp): Add comment dumps.
(JSC::CodeBlock::printBinaryOp): Add comment dumps.
(JSC::CodeBlock::printConditionalJump): Add comment dumps.
(JSC::CodeBlock::printCallOp): Add comment dumps.
(JSC::CodeBlock::printPutByIdOp): Add comment dumps.
(JSC::CodeBlock::dump): Add comment dumps.
(JSC::CodeBlock::CodeBlock):
(JSC::CodeBlock::commentForBytecodeOffset):

Finds the comment for an opcode if available.

(JSC::CodeBlock::dumpBytecodeComments):

For debugging whether comments are collected.
It is not being called anywhere.

• bytecode/CodeBlock.h:

(CodeBlock):
(JSC::CodeBlock::bytecodeComments):

• bytecode/Comment.h: Added.

(JSC):
(Comment):

• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::emitOpcode): Calls emitComment().
(JSC):
(JSC::BytecodeGenerator::emitComment): Adds comment to CodeBlock.
(JSC::BytecodeGenerator::prependComment):

Registers a comment for emitComemnt() to use later.

• bytecompiler/BytecodeGenerator.h:

(BytecodeGenerator):
(JSC::BytecodeGenerator::emitComment):
(JSC::BytecodeGenerator::prependComment):

These are inlined versions of these functions that nullify them
when ENABLE_BYTECODE_COMMENTS is 0.

(JSC::BytecodeGenerator::comments):

File:

• trunk/Source/JavaScriptCore/bytecode/CodeBlock.h (modified) (5 diffs)

trunk/Source/JavaScriptCore/bytecode/CodeBlock.h

@@ -36 +36 @@
 #include "CodeOrigin.h"
 #include "CodeType.h"
+#include "Comment.h"
 #include "CompactJITCodeMap.h"
 #include "DFGCodeBlocks.h"
@@ -67 +68 @@
 #include <wtf/FastAllocBase.h>
 #include <wtf/PassOwnPtr.h>
+#include <wtf/Platform.h>
 #include <wtf/RefPtr.h>
 #include <wtf/SegmentedVector.h>
 #include <wtf/Vector.h>
+
+// Set ENABLE_BYTECODE_COMMENTS to 1 to enable recording bytecode generator
+// comments for the bytecodes that it generates. This will allow
+// CodeBlock::dump() to provide some contextual info about the bytecodes.
+//
+// The way this comment system works is as follows:
+// 1. The BytecodeGenerator calls prependComment() with a constant comment
+//    string in .text. The string must not be a stack or heap allocated
+//    string.
+// 2. When the BytecodeGenerator's emitOpcode() is called, the last
+//    prepended comment will be recorded with the PC of the opcode being
+//    emitted. This comment is being recorded in the CodeBlock's
+//    m_bytecodeComments.
+// 3. When CodeBlock::dump() is called, it will pair up the comments with
+//    their corresponding bytecodes based on the bytecode and comment's
+//    PC. If a matching pair is found, the comment will be printed after
+//    the bytecode. If not, no comment is printed.
+//
+// NOTE: Enabling this will consume additional memory at runtime to store
+// the comments. Since these comments are only useful for VM debugging
+// (as opposed to app debugging), this feature is to be disabled by default,
+// and can be enabled as needed for VM development use only.
+
+#define ENABLE_BYTECODE_COMMENTS 0
 
 namespace JSC {
@@ -155 +181 @@
             return index >= m_numVars;
         }
+
+        void dumpBytecodeCommentAndNewLine(int location);
+#if ENABLE(BYTECODE_COMMENTS)
+        const char* commentForBytecodeOffset(unsigned bytecodeOffset);
+        void dumpBytecodeComments();
+#endif
 
         HandlerInfo* handlerForBytecodeOffset(unsigned bytecodeOffset);
@@ -366 +398 @@
         const RefCountedArray<Instruction>& instructions() const { return m_instructions; }
         
+#if ENABLE(BYTECODE_COMMENTS)
+        Vector<Comment>& bytecodeComments() { return m_bytecodeComments; }
+#endif
+
         size_t predictedMachineCodeSize();
         
@@ -1303 +1339 @@
 
         Vector<LineInfo> m_lineInfo;
+#if ENABLE(BYTECODE_COMMENTS)
+        Vector<Comment>  m_bytecodeComments;
+        size_t m_bytecodeCommentIterator;
+#endif
 
         struct RareData {