Changeset 35230 in webkit for trunk/JavaScriptCore/VM/CodeGenerator.cpp

Timestamp:

Jul 17, 2008, 4:53:39 PM (17 years ago)

Author:

[email protected]

Message:

2008-07-17 Geoffrey Garen <​[email protected]>

Reviewed by John Sullivan and Oliver Hunt.

A tiny bit of tidying in function call register allocation.

This patch saves one register when invoking a function expression and/or
a new expression that is stored in a temporary.

Since it's just one register, I can't make a testcase for it.

• VM/CodeGenerator.cpp: (KJS::CodeGenerator::emitCall): No need to ref the function we're calling or its base. We'd like the call frame to overlap with them, if possible. op_call will read the function and its base before writing the call frame, so this is safe.

• kjs/nodes.cpp: (KJS::NewExprNode::emitCode): No need to ref the function we're new-ing, for the same reasons stated above.

(KJS::FunctionCallValueNode::emitCode): ditto

File:

• trunk/JavaScriptCore/VM/CodeGenerator.cpp (modified) (2 diffs)

trunk/JavaScriptCore/VM/CodeGenerator.cpp

@@ -863 +863 @@
 {
     ASSERT(opcodeID == op_call || opcodeID == op_call_eval);
-
-    RefPtr<RegisterID> refFunc = func;
-    RefPtr<RegisterID> refBase = base;
+    
+    // Ordinarily, we might ref "func" and "base", to avoid allocating new
+    // temporaries in the same registers. In this case, though, we actually
+    // want the call frame we allocate to overlap "func" and "base", if they're
+    // not otherwise referenced. op_call will read "func" and "base" before
+    // writing out the call frame, so this is safe.
 
     // Reserve space for call frame.
@@ -898 +901 @@
 RegisterID* CodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func, ArgumentsNode* argumentsNode)
 {
+    // Ordinarily, we might ref "func", to avoid allocating a new temporary in
+    // the same register. In this case, though, we actually want the call
+    // frame we allocate to overlap "func", if it's not otherwise referenced.
+    // op_construct will read "func" before writing out the call frame, so this
+    // is safe.
+
     // Reserve space for call frame.
     Vector<RefPtr<RegisterID>, RegisterFile::CallFrameHeaderSize> callFrame;