Changes between Version 51 and Version 52 of squirrelfish

Timestamp:

Apr 7, 2008, 2:20:31 PM (18 years ago)

Author:

oliver@apple.com

Comment:

--

squirrelfish

@@ -201 +201 @@
 
 {{{
-Revision 31432 was a 1.4% performance regression because it moved the register vector from a local to a parameter. Making the register vector a data member has the same effect. WTF?
-
-}}}
-
+Revision 31432 was a 1.4% performance regression because it moved the register vector from a
+local to a parameter. Making the register vector a data member has the same effect. WTF?
+}}}
+
+{{{
+Exception handling throw logic has to pass vPC to a function, and assign the result to vPC, eg.
+  if (!(vPC = throwException(codeBlock, k, scopeChain, registers, r, vPC)))
+But this causes a 25% regression on the above empty-for-loop test, despite never being hit.  
+To avoid this we need to do:
+void* throwTarget;
+...
+void Machine::privateExecute(..)
+{
+    ...
+    // in address table initialiser
+    throwTarget = &&gcc_dependency_hack;
+    ...
+    BEGIN_OPCODE(op_throw) {
+        ...
+        if (!(exceptionTarget = throwException(codeBlock, k, scopeChain, registers, r, vPC))) { ... }
+        ...
+        goto *throwTarget;
+    }
+    gcc_dependency_hack:
+    {
+        vPC = exceptionTarget;
+        NEXT_OPCODE;
+    }
+}
+
+Without this _indirect_ goto we get a 25% regression, if we use a direct goto we still get an 18% regression.
+
+}}}