Changeset 256498 in webkit for trunk/Source/JavaScriptCore/jit/JIT.cpp

Timestamp:

Feb 12, 2020, 6:30:05 PM (5 years ago)

Author:

[email protected]

Message:

[JSC] Compact JITCodeMap by storing BytecodeIndex and CodeLocation separately
​https://bugs.webkit.org/show_bug.cgi?id=207673

Reviewed by Mark Lam.

Source/JavaScriptCore:

While BytecodeIndex is 4 bytes, CodeLocation is 8 bytes. So the tuple of them "JITCodeMap::Entry"
becomes 16 bytes because it adds 4 bytes padding. We should store BytecodeIndex and CodeLocation separately
to avoid this padding.

This patch introduces JITCodeMapBuilder. We use this to build JITCodeMap data structure as a immutable final result.

• jit/JIT.cpp:

(JSC::JIT::link):

• jit/JITCodeMap.h:

(JSC::JITCodeMap::JITCodeMap):
(JSC::JITCodeMap::find const):
(JSC::JITCodeMap::operator bool const):
(JSC::JITCodeMap::codeLocations const):
(JSC::JITCodeMap::indexes const):
(JSC::JITCodeMapBuilder::append):
(JSC::JITCodeMapBuilder::finalize):
(JSC::JITCodeMap::Entry::Entry): Deleted.
(JSC::JITCodeMap::Entry::bytecodeIndex const): Deleted.
(JSC::JITCodeMap::Entry::codeLocation): Deleted.
(JSC::JITCodeMap::append): Deleted.
(JSC::JITCodeMap::finish): Deleted.

Source/WTF:

• wtf/MallocPtr.h:

File:

• trunk/Source/JavaScriptCore/jit/JIT.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/jit/JIT.cpp

@@ -913 +913 @@
     }
 
-    JITCodeMap jitCodeMap;
-    for (unsigned bytecodeOffset = 0; bytecodeOffset < m_labels.size(); ++bytecodeOffset) {
-        if (m_labels[bytecodeOffset].isSet())
-            jitCodeMap.append(BytecodeIndex(bytecodeOffset), patchBuffer.locationOf<JSEntryPtrTag>(m_labels[bytecodeOffset]));
-    }
-    jitCodeMap.finish();
-    m_codeBlock->setJITCodeMap(WTFMove(jitCodeMap));
+    {
+        JITCodeMapBuilder jitCodeMapBuilder;
+        for (unsigned bytecodeOffset = 0; bytecodeOffset < m_labels.size(); ++bytecodeOffset) {
+            if (m_labels[bytecodeOffset].isSet())
+                jitCodeMapBuilder.append(BytecodeIndex(bytecodeOffset), patchBuffer.locationOf<JSEntryPtrTag>(m_labels[bytecodeOffset]));
+        }
+        m_codeBlock->setJITCodeMap(jitCodeMapBuilder.finalize());
+    }
 
     MacroAssemblerCodePtr<JSEntryPtrTag> withArityCheck = patchBuffer.locationOf<JSEntryPtrTag>(m_arityCheck);