Changeset 43885 in webkit for trunk/JavaScriptCore/interpreter/RegisterFile.h

Timestamp:

May 19, 2009, 8:25:47 PM (16 years ago)

Author:

[email protected]

Message:

2009-05-19 Geoffrey Garen <​[email protected]>

Reviewed by Sam Weinig.

Fixed <rdar://problem/6885680> CrashTracer: [USER] 1 crash in Install
Mac OS X at <unknown binary> • 0x9274241c

(Original patch by Joe Sokol and Ronnie Misra.)

SunSpider says 1.004x faster.

• interpreter/RegisterFile.cpp: (JSC::RegisterFile::releaseExcessCapacity): Instead of doing complicated math that sometimes used to overflow, just release the full range of the register file.

• interpreter/RegisterFile.h: (JSC::isPageAligned): (JSC::RegisterFile::RegisterFile): Added ASSERTs to verify that it's safe to release the full range of the register file.

(JSC::RegisterFile::shrink): No need to releaseExcessCapacity() if the
new end is not smaller than the old end. (Also, doing so used to cause
numeric overflow, unmapping basically the whole process from memory.)

File:

• trunk/JavaScriptCore/interpreter/RegisterFile.h (modified) (3 diffs)

trunk/JavaScriptCore/interpreter/RegisterFile.h

@@ -157 +157 @@
     };
 
+    // FIXME: Add a generic getpagesize() to WTF, then move this function to WTF as well.
+    inline bool isPageAligned(size_t size) { return size != 0 && size % (8 * 1024) == 0; }
+
     inline RegisterFile::RegisterFile(size_t capacity, size_t maxGlobals)
         : m_numGlobals(0)
@@ -166 +169 @@
         , m_globalObject(0)
     {
+        // Verify that our values will play nice with mmap and VirtualAlloc.
+        ASSERT(isPageAligned(maxGlobals));
+        ASSERT(isPageAligned(capacity));
+
         size_t bufferLength = (capacity + maxGlobals) * sizeof(Register);
     #if HAVE(MMAP)
@@ -197 +204 @@
     inline void RegisterFile::shrink(Register* newEnd)
     {
-        if (newEnd < m_end)
-            m_end = newEnd;
-        if (m_end == m_start && (m_maxUsed - m_start) > maxExcessCapacity) 
+        if (newEnd >= m_end)
+            return;
+        m_end = newEnd;
+        if (m_end == m_start && (m_maxUsed - m_start) > maxExcessCapacity)
             releaseExcessCapacity();
     }