Simplify handling of exits from with and catch.

src/ia32/macro-assembler-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 524 matching lines @@
   mov(esp, Operand(ebp));
   pop(ebp);
 
   LeaveExitFrameEpilogue();
 }
 
 
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                     HandlerType type) {
   // Adjust this code if not the case.
-  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // The pc (return address) is already on TOS.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
       push(Immediate(StackHandler::TRY_CATCH));
     } else {
       push(Immediate(StackHandler::TRY_FINALLY));
     }
     push(ebp);
+    push(esi);
   } else {
     ASSERT(try_location == IN_JS_ENTRY);
     // The frame pointer does not point to a JS frame so we save NULL
     // for ebp. We expect the code throwing an exception to check ebp
     // before dereferencing it to restore the context.
     push(Immediate(StackHandler::ENTRY));
     push(Immediate(0));  // NULL frame pointer.
+    push(Immediate(Smi::FromInt(0)));  // No context.
   }
   // Save the current handler as the next handler.
   push(Operand::StaticVariable(ExternalReference(Isolate::k_handler_address,
                                                  isolate())));
   // Link this handler as the new current one.
   mov(Operand::StaticVariable(ExternalReference(Isolate::k_handler_address,
                                                 isolate())),
       esp);
 }
 
 
 void MacroAssembler::PopTryHandler() {
-  ASSERT_EQ(0, StackHandlerConstants::kNextOffset);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(Operand::StaticVariable(ExternalReference(Isolate::k_handler_address,
                                                 isolate())));
   add(Operand(esp), Immediate(StackHandlerConstants::kSize - kPointerSize));
 }
 
 
 void MacroAssembler::Throw(Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
-
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // eax must hold the exception.
   if (!value.is(eax)) {
     mov(eax, value);
   }
 
   // Drop the sp to the top of the handler.
   ExternalReference handler_address(Isolate::k_handler_address,
                                     isolate());
   mov(esp, Operand::StaticVariable(handler_address));
 
-  // Restore next handler and frame pointer, discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  // Restore next handler, context, and frame pointer; discard handler state.
   pop(Operand::StaticVariable(handler_address));
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
-  pop(ebp);
-  pop(edx);  // Remove state.
+  pop(esi);  // Context.
+  pop(ebp);  // Frame pointer.
+  pop(edx);  // State.
 
-  // Before returning we restore the context from the frame pointer if
-  // not NULL.  The frame pointer is NULL in the exception handler of
-  // a JS entry frame.
-  Set(esi, Immediate(0));  // Tentatively set context pointer to NULL.
+  // If the handler is a JS frame, restore the context to the frame.
+  // (edx == ENTRY) == (ebp == 0) == (esi == 0), so we could test any
+  // of them.
   Label skip;
-  cmp(ebp, 0);
+  cmp(Operand(edx), Immediate(StackHandler::ENTRY));
   j(equal, &skip, Label::kNear);
-  mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
+  mov(Operand(ebp, StandardFrameConstants::kContextOffset), esi);
   bind(&skip);
 
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   ret(0);
 }
 
 
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
   // Adjust this code if not the case.
-  STATIC_ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
 
   // eax must hold the exception.
   if (!value.is(eax)) {
     mov(eax, value);
   }
 
   // Drop sp to the top stack handler.
   ExternalReference handler_address(Isolate::k_handler_address,
                                     isolate());
   mov(esp, Operand::StaticVariable(handler_address));
 
   // Unwind the handlers until the ENTRY handler is found.
   Label loop, done;
   bind(&loop);
   // Load the type of the current stack handler.
   const int kStateOffset = StackHandlerConstants::kStateOffset;
   cmp(Operand(esp, kStateOffset), Immediate(StackHandler::ENTRY));
   j(equal, &done, Label::kNear);
   // Fetch the next handler in the list.
   const int kNextOffset = StackHandlerConstants::kNextOffset;
   mov(esp, Operand(esp, kNextOffset));
   jmp(&loop);
   bind(&done);
 
   // Set the top handler address to next handler past the current ENTRY handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
   pop(Operand::StaticVariable(handler_address));
 
   if (type == OUT_OF_MEMORY) {
     // Set external caught exception to false.
     ExternalReference external_caught(
         Isolate::k_external_caught_exception_address,
         isolate());
     mov(eax, false);
     mov(Operand::StaticVariable(external_caught), eax);
 
     // Set pending exception and eax to out of memory exception.
     ExternalReference pending_exception(Isolate::k_pending_exception_address,
                                         isolate());
     mov(eax, reinterpret_cast<int32_t>(Failure::OutOfMemoryException()));
     mov(Operand::StaticVariable(pending_exception), eax);
   }
 
-  // Clear the context pointer.
+  // Discard the context saved in the handler and clear the context pointer.
+  pop(edx);
   Set(esi, Immediate(0));
 
   // Restore fp from handler and discard handler state.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 1 * kPointerSize);
   pop(ebp);
   pop(edx);  // State.
 
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   ret(0);
 }
 
 
 void MacroAssembler::CheckAccessGlobalProxy(Register holder_reg,
                                             Register scratch,
                                             Label* miss) {
   Label same_contexts;
 
   ASSERT(!holder_reg.is(scratch));
@@ skipping 1555 matching lines @@
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32