Changeset 195365 in webkit

Timestamp:

Jan 20, 2016 12:27:01 PM (8 years ago)

Author:

akling@apple.com

Message:

Pack RegisterAtOffset harder.
<​https://webkit.org/b/152501>

Reviewed by Michael Saboff.

Pack the register index and the offset into a single pointer-sized word instead of two.
This reduces memory consumption by 620 kB on mobile theverge.com.

The packing doesn't succeed on MSVC for some reason, so I've left out the static
assertion about class size in those builds.

• jit/RegisterAtOffset.cpp:
• jit/RegisterAtOffset.h:

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• jit/RegisterAtOffset.cpp (modified) (1 diff)
• jit/RegisterAtOffset.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2016-01-20  Andreas Kling  <akling@apple.com>
+
+        Pack RegisterAtOffset harder.
+        <https://webkit.org/b/152501>
+
+        Reviewed by Michael Saboff.
+
+        Pack the register index and the offset into a single pointer-sized word instead of two.
+        This reduces memory consumption by 620 kB on mobile theverge.com.
+
+        The packing doesn't succeed on MSVC for some reason, so I've left out the static
+        assertion about class size in those builds.
+
+        * jit/RegisterAtOffset.cpp:
+        * jit/RegisterAtOffset.h:
+
 2016-01-20  Per Arne Vollan  <peavo@outlook.com>
 

trunk/Source/JavaScriptCore/jit/RegisterAtOffset.cpp

@@ -31 +31 @@
 namespace JSC {
 
+#if !COMPILER(MSVC)
+static_assert(sizeof(RegisterAtOffset) == sizeof(ptrdiff_t), "RegisterAtOffset should be small.");
+#endif
+
 void RegisterAtOffset::dump(PrintStream& out) const
 {

trunk/Source/JavaScriptCore/jit/RegisterAtOffset.h

@@ -71 +71 @@
 private:
     Reg m_reg;
-    ptrdiff_t m_offset;
+    ptrdiff_t m_offset : sizeof(ptrdiff_t) * 8 - sizeof(Reg) * 8;
 };