Fix ABI for API calls on ia32.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index feb82684eaf52df66c83a4fcdadc39d188d49b0c..e3df6815b75c5d9683504f0d0eb0d25db4096193 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1429,9 +1429,6 @@ void MacroAssembler::PrepareCallApiFunction(int argc, Register scratch) {
     //   1: arg1
     //   0: pointer to the output cell
     //
-    // Note that this is one more "argument" than the function expects
-    // so the out cell will have to be popped explicitly after returning
-    // from the function. The out cell contains Handle.
 
     // pointer to out cell.
     lea(scratch, Operand(esp, (argc + 1) * kPointerSize));
@@ -1444,6 +1441,7 @@ void MacroAssembler::PrepareCallApiFunction(int argc, Register scratch) {
 
 
 MaybeObject* MacroAssembler::TryCallApiFunctionAndReturn(ApiFunction* function,
+                                                         int argc,
                                                          int stack_space) {
   ExternalReference next_address =
       ExternalReference::handle_scope_next_address();
@@ -1452,6 +1450,11 @@ MaybeObject* MacroAssembler::TryCallApiFunctionAndReturn(ApiFunction* function,
   ExternalReference level_address =
       ExternalReference::handle_scope_level_address();
 
+  // Save out slot address in the callee-save register.

[Vitaly Repeshko, 2011/07/04 22:41:36]

Let's be consistent with "slot" vs. "cell" here in the function above. I prefer
"slot".

[Vyacheslav Egorov (Chromium), 2011/07/05 11:03:50]

Done.

+  if (!kReturnHandlesDirectly) {
+    lea(esi, Operand(esp, (argc + 1) * kPointerSize));

[Vitaly Repeshko, 2011/07/04 22:41:36]

This is tightly coupled to PrepareCallApiFunction. Its comments already
(incorrectly it seems) say it uses esi to restore the original stack state. How
about moving this block to PrepareCallApiFunction? This way we can avoid passing
the confusing argc here.
Also for debugging purposes it may be useful to clobber esi even if
kReturnHandlesDirectly is true (in debug mode).

[Vyacheslav Egorov (Chromium), 2011/07/05 11:03:50]

I though about that but did not want to prolong esi liverange. 

Done.

+  }
+
   // Allocate HandleScope in callee-save registers.
   mov(ebx, Operand::StaticVariable(next_address));
   mov(edi, Operand::StaticVariable(limit_address));
@@ -1461,9 +1464,7 @@ MaybeObject* MacroAssembler::TryCallApiFunctionAndReturn(ApiFunction* function,
   call(function->address(), RelocInfo::RUNTIME_ENTRY);
 
   if (!kReturnHandlesDirectly) {
-    // The returned value is a pointer to the handle holding the result.
-    // Dereference this to get to the location.
-    mov(eax, Operand(eax, 0));
+    mov(eax, Operand(esi, 0));

[Vitaly Repeshko, 2011/07/04 22:41:36]

Some comment here would be helpful.

[Vyacheslav Egorov (Chromium), 2011/07/05 11:03:50]

Done.

   }
 
   Label empty_handle;