Simplify handling of exits from with and catch.

src/x64/macro-assembler-x64.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 2369 matching lines @@
 
 
 Operand MacroAssembler::SafepointRegisterSlot(Register reg) {
   return Operand(rsp, SafepointRegisterStackIndex(reg.code()) * kPointerSize);
 }
 
 
 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 * kPointerSize);
+  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.  This code pushes state,
-  // frame pointer and current handler.  Check that they are expected
-  // next on the stack, in that order.
-  ASSERT_EQ(StackHandlerConstants::kStateOffset,
-            StackHandlerConstants::kPCOffset - kPointerSize);
-  ASSERT_EQ(StackHandlerConstants::kFPOffset,
-            StackHandlerConstants::kStateOffset - kPointerSize);
-  ASSERT_EQ(StackHandlerConstants::kNextOffset,
-            StackHandlerConstants::kFPOffset - kPointerSize);
-
+  // frame pointer, context, and current handler.
   if (try_location == IN_JAVASCRIPT) {
     if (type == TRY_CATCH_HANDLER) {
       push(Immediate(StackHandler::TRY_CATCH));
     } else {
       push(Immediate(StackHandler::TRY_FINALLY));
     }
     push(rbp);
+    push(rsi);
   } else {
     ASSERT(try_location == IN_JS_ENTRY);
     // The frame pointer does not point to a JS frame so we save NULL
     // for rbp. We expect the code throwing an exception to check rbp
     // before dereferencing it to restore the context.
     push(Immediate(StackHandler::ENTRY));
     push(Immediate(0));  // NULL frame pointer.
+    Push(Smi::FromInt(0));  // No context.
   }
   // Save the current handler.
   Operand handler_operand =
       ExternalOperand(ExternalReference(Isolate::k_handler_address, isolate()));
   push(handler_operand);
   // Link this handler.
   movq(handler_operand, rsp);
 }
 
 
 void MacroAssembler::PopTryHandler() {
   ASSERT_EQ(0, StackHandlerConstants::kNextOffset);
   // Unlink this handler.
   Operand handler_operand =
       ExternalOperand(ExternalReference(Isolate::k_handler_address, isolate()));
   pop(handler_operand);
   // Remove the remaining fields.
   addq(rsp, Immediate(StackHandlerConstants::kSize - kPointerSize));
 }
 
 
 void MacroAssembler::Throw(Register value) {
-  // Check that stack should contain next handler, frame pointer, state and
-  // return address in that order.
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset + kPointerSize ==
-            StackHandlerConstants::kStateOffset);
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset + kPointerSize ==
-            StackHandlerConstants::kPCOffset);
+  // Adjust this code if not the case.
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // Keep thrown value in rax.
   if (!value.is(rax)) {
     movq(rax, value);
   }
 
   ExternalReference handler_address(Isolate::k_handler_address, isolate());
   Operand handler_operand = ExternalOperand(handler_address);
   movq(rsp, handler_operand);
   // get next in chain
   pop(handler_operand);
-  pop(rbp);  // pop frame pointer
-  pop(rdx);  // remove state
+  pop(rsi);  // Context.
+  pop(rbp);  // Frame pointer.
+  pop(rdx);  // 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(rsi, 0);  // Tentatively set context pointer to NULL
+  // If the handler is a JS frame, restore the context to the frame.
+  // (rdx == ENTRY) == (rbp == 0) == (rsi == 0), so we could test any
+  // of them.
   Label skip;
-  cmpq(rbp, Immediate(0));
+  cmpq(rdx, Immediate(StackHandler::ENTRY));
   j(equal, &skip, Label::kNear);
-  movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+  movq(Operand(rbp, StandardFrameConstants::kContextOffset), rsi);
   bind(&skip);
+
   ret(0);
 }
 
 
 void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
                                       Register value) {
+  // Adjust this code if not the case.
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
   // Keep thrown value in rax.
   if (!value.is(rax)) {
     movq(rax, value);
   }
   // Fetch top stack handler.
   ExternalReference handler_address(Isolate::k_handler_address, isolate());
   Load(rsp, handler_address);
 
   // Unwind the handlers until the ENTRY handler is found.
   Label loop, done;
@@ skipping 19 matching lines @@
     Set(rax, static_cast<int64_t>(false));
     Store(external_caught, rax);
 
     // Set pending exception and rax to out of memory exception.
     ExternalReference pending_exception(Isolate::k_pending_exception_address,
                                         isolate());
     movq(rax, Failure::OutOfMemoryException(), RelocInfo::NONE);
     Store(pending_exception, rax);
   }
 
-  // Clear the context pointer.
+  // Discard the context saved in the handler and clear the context pointer.
+  pop(rdx);
   Set(rsi, 0);
 
-  // Restore registers from handler.
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset + kPointerSize ==
-                StackHandlerConstants::kFPOffset);
-  pop(rbp);  // FP
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset + kPointerSize ==
-                StackHandlerConstants::kStateOffset);
-  pop(rdx);  // State
+  pop(rbp);  // Restore frame pointer.
+  pop(rdx);  // Discard state.
 
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset + kPointerSize ==
-                StackHandlerConstants::kPCOffset);
   ret(0);
 }
 
 
 void MacroAssembler::Ret() {
   ret(0);
 }
 
 
 void MacroAssembler::Ret(int bytes_dropped, Register scratch) {
@@ skipping 1316 matching lines @@
   CPU::FlushICache(address_, size_);
 
   // 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_X64