Cleanup of ARM exception handlers. Remove the unused code and...

src/arm/codegen-arm.cc

 // Copyright 2006-2009 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 2089 matching lines @@
   bool has_unlinks = false;
   for (int i = 0; i < shadows.length(); i++) {
     shadows[i]->StopShadowing();
     has_unlinks = has_unlinks || shadows[i]->is_linked();
   }
   function_return_is_shadowed_ = function_return_was_shadowed;
 
   // Get an external reference to the handler address.
   ExternalReference handler_address(Top::k_handler_address);
 
-  // The next handler address is at kNextIndex in the stack.
-  const int kNextIndex = StackHandlerConstants::kNextOffset / kPointerSize;
   // If we can fall off the end of the try block, unlink from try chain.
   if (has_valid_frame()) {
-    __ ldr(r1, frame_->ElementAt(kNextIndex));
+    // The next handler address is on top of the frame.  Unlink from
+    // the handler list and drop the rest of this handler from the
+    // frame.
+    ASSERT(StackHandlerConstants::kNextOffset == 0);
+    frame_->EmitPop(r1);
     __ mov(r3, Operand(handler_address));
     __ str(r1, MemOperand(r3));
-    frame_->Drop(StackHandlerConstants::kSize / kPointerSize);
+    frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
     if (has_unlinks) {
       exit.Jump();
     }
   }
 
   // Generate unlink code for the (formerly) shadowing labels that have been
   // jumped to.  Deallocate each shadow target.
   for (int i = 0; i < shadows.length(); i++) {
     if (shadows[i]->is_linked()) {
       // Unlink from try chain;
       shadows[i]->Bind();
       // Because we can be jumping here (to spilled code) from unspilled
       // code, we need to reestablish a spilled frame at this block.
       frame_->SpillAll();
 
       // Reload sp from the top handler, because some statements that we
       // break from (eg, for...in) may have left stuff on the stack.
       __ mov(r3, Operand(handler_address));
       __ ldr(sp, MemOperand(r3));
-      // The stack pointer was restored to just below the code slot
-      // (the topmost slot) in the handler.
-      frame_->Forget(frame_->height() - handler_height + 1);
+      frame_->Forget(frame_->height() - handler_height);
 
-      // kNextIndex is off by one because the code slot has already
-      // been dropped.
-      __ ldr(r1, frame_->ElementAt(kNextIndex - 1));
+      ASSERT(StackHandlerConstants::kNextOffset == 0);
+      frame_->EmitPop(r1);
       __ str(r1, MemOperand(r3));
-      // The code slot has already been dropped from the handler.
       frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
 
       if (!function_return_is_shadowed_ && i == kReturnShadowIndex) {
         frame_->PrepareForReturn();
       }
       shadows[i]->other_target()->Jump();
     }
   }
 
   exit.Bind();
@@ skipping 60 matching lines @@
   int nof_unlinks = 0;
   for (int i = 0; i < shadows.length(); i++) {
     shadows[i]->StopShadowing();
     if (shadows[i]->is_linked()) nof_unlinks++;
   }
   function_return_is_shadowed_ = function_return_was_shadowed;
 
   // Get an external reference to the handler address.
   ExternalReference handler_address(Top::k_handler_address);
 
-  // The next handler address is at kNextIndex in the stack.
-  const int kNextIndex = StackHandlerConstants::kNextOffset / kPointerSize;
   // If we can fall off the end of the try block, unlink from the try
   // chain and set the state on the frame to FALLING.
   if (has_valid_frame()) {
-    __ ldr(r1, frame_->ElementAt(kNextIndex));
+    // The next handler address is on top of the frame.
+    ASSERT(StackHandlerConstants::kNextOffset == 0);
+    frame_->EmitPop(r1);
     __ mov(r3, Operand(handler_address));
     __ str(r1, MemOperand(r3));
-    frame_->Drop(StackHandlerConstants::kSize / kPointerSize);
+    frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
 
     // Fake a top of stack value (unneeded when FALLING) and set the
     // state in r2, then jump around the unlink blocks if any.
     __ mov(r0, Operand(Factory::undefined_value()));
     frame_->EmitPush(r0);
     __ mov(r2, Operand(Smi::FromInt(FALLING)));
     if (nof_unlinks > 0) {
       finally_block.Jump();
     }
   }
@@ skipping 10 matching lines @@
       // unspilled code, we need to reestablish a spilled frame at
       // this block.
       shadows[i]->Bind();
       frame_->SpillAll();
 
       // Reload sp from the top handler, because some statements that
       // we break from (eg, for...in) may have left stuff on the
       // stack.
       __ mov(r3, Operand(handler_address));
       __ ldr(sp, MemOperand(r3));
-      // The stack pointer was restored to the address slot in the handler.
-      ASSERT(StackHandlerConstants::kNextOffset == 1 * kPointerSize);
-      frame_->Forget(frame_->height() - handler_height + 1);
+      frame_->Forget(frame_->height() - handler_height);
 
       // Unlink this handler and drop it from the frame.  The next
-      // handler address is now on top of the frame.
+      // handler address is currently on top of the frame.
+      ASSERT(StackHandlerConstants::kNextOffset == 0);
       frame_->EmitPop(r1);
       __ str(r1, MemOperand(r3));
-      // The top (code) and the second (handler) slot have both been
-      // dropped already.
-      frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 2);
+      frame_->Drop(StackHandlerConstants::kSize / kPointerSize - 1);
 
       if (i == kReturnShadowIndex) {
         // If this label shadowed the function return, materialize the
         // return value on the stack.
         frame_->EmitPush(r0);
       } else {
         // Fake TOS for targets that shadowed breaks and continues.
         __ mov(r0, Operand(Factory::undefined_value()));
         frame_->EmitPush(r0);
       }
@@ skipping 2386 matching lines @@
   __ push(r0);
   __ mov(r0, Operand(0));  // set number of arguments
   __ InvokeBuiltin(Builtins::UNARY_MINUS, JUMP_JS);
 
   __ bind(&done);
   __ StubReturn(1);
 }
 
 
 void CEntryStub::GenerateThrowTOS(MacroAssembler* masm) {
-  // r0 holds exception
-  ASSERT(StackHandlerConstants::kSize == 6 * kPointerSize);  // adjust this code
+  // r0 holds the exception.
+
+  // Adjust this code if not the case.
+  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+
+  // Drop the sp to the top of the handler.
   __ mov(r3, Operand(ExternalReference(Top::k_handler_address)));
   __ ldr(sp, MemOperand(r3));
-  __ pop(r2);  // pop next in chain
+
+  // Restore the next handler and frame pointer, discard handler state.
+  ASSERT(StackHandlerConstants::kNextOffset == 0);
+  __ pop(r2);
   __ str(r2, MemOperand(r3));
-  // restore parameter- and frame-pointer and pop state.
-  __ ldm(ia_w, sp, r3.bit() | pp.bit() | fp.bit());
-  // 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.
+  ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  __ ldm(ia_w, sp, r3.bit() | fp.bit());  // r3: discarded 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.
   __ cmp(fp, Operand(0));
   // Set cp to NULL if fp is NULL.
   __ mov(cp, Operand(0), LeaveCC, eq);
   // Restore cp otherwise.
   __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
 #ifdef DEBUG
   if (FLAG_debug_code) {
     __ mov(lr, Operand(pc));
   }
 #endif
+  ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   __ pop(pc);
 }
 
 
 void CEntryStub::GenerateThrowOutOfMemory(MacroAssembler* masm) {
-  // Fetch top stack handler.
+  // Adjust this code if not the case.
+  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);
+
+  // Drop sp to the top stack handler.
   __ mov(r3, Operand(ExternalReference(Top::k_handler_address)));
-  __ ldr(r3, MemOperand(r3));
+  __ ldr(sp, MemOperand(r3));
 
   // 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::kAddressDisplacement +
-      StackHandlerConstants::kStateOffset;
-  __ ldr(r2, MemOperand(r3, kStateOffset));
+  const int kStateOffset = StackHandlerConstants::kStateOffset;
+  __ ldr(r2, MemOperand(sp, kStateOffset));
   __ cmp(r2, Operand(StackHandler::ENTRY));
   __ b(eq, &done);
   // Fetch the next handler in the list.
-  const int kNextOffset =  StackHandlerConstants::kAddressDisplacement +
-      StackHandlerConstants::kNextOffset;
-  __ ldr(r3, MemOperand(r3, kNextOffset));
+  const int kNextOffset = StackHandlerConstants::kNextOffset;
+  __ ldr(sp, MemOperand(sp, kNextOffset));
   __ jmp(&loop);
   __ bind(&done);
 
   // Set the top handler address to next handler past the current ENTRY handler.
-  __ ldr(r0, MemOperand(r3, kNextOffset));
-  __ mov(r2, Operand(ExternalReference(Top::k_handler_address)));
-  __ str(r0, MemOperand(r2));
+  ASSERT(StackHandlerConstants::kNextOffset == 0);
+  __ pop(r0);
+  __ str(r0, MemOperand(r3));
 
   // Set external caught exception to false.
+  ExternalReference external_caught(Top::k_external_caught_exception_address);
   __ mov(r0, Operand(false));
-  ExternalReference external_caught(Top::k_external_caught_exception_address);
   __ mov(r2, Operand(external_caught));
   __ str(r0, MemOperand(r2));
 
   // Set pending exception and r0 to out of memory exception.
   Failure* out_of_memory = Failure::OutOfMemoryException();
   __ mov(r0, Operand(reinterpret_cast<int32_t>(out_of_memory)));
   __ mov(r2, Operand(ExternalReference(Top::k_pending_exception_address)));
   __ str(r0, MemOperand(r2));
 
-  // Restore the stack to the address of the ENTRY handler
-  __ mov(sp, Operand(r3));
+  // Stack layout at this point. See also StackHandlerConstants.
+  // sp ->   state (ENTRY)
+  //         fp
+  //         lr
 
-  // Stack layout at this point. See also PushTryHandler
-  // r3, sp ->   next handler
-  //             state (ENTRY)
-  //             pp
-  //             fp
-  //             lr
-
-  // Discard ENTRY state (r2 is not used), and restore parameter-
-  // and frame-pointer and pop state.
-  __ ldm(ia_w, sp, r2.bit() | r3.bit() | pp.bit() | fp.bit());
-  // 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.
+  // Discard handler state (r2 is not used) and restore frame pointer.
+  ASSERT(StackHandlerConstants::kFPOffset == 2 * kPointerSize);
+  __ ldm(ia_w, sp, r2.bit() | fp.bit());  // r2: discarded 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.
   __ cmp(fp, Operand(0));
   // Set cp to NULL if fp is NULL.
   __ mov(cp, Operand(0), LeaveCC, eq);
   // Restore cp otherwise.
   __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
 #ifdef DEBUG
   if (FLAG_debug_code) {
     __ mov(lr, Operand(pc));
   }
 #endif
+  ASSERT(StackHandlerConstants::kPCOffset == 3 * kPointerSize);
   __ pop(pc);
 }
 
 
 void CEntryStub::GenerateCore(MacroAssembler* masm,
                               Label* throw_normal_exception,
                               Label* throw_out_of_memory_exception,
                               StackFrame::Type frame_type,
                               bool do_gc,
                               bool always_allocate) {
@@ skipping 397 matching lines @@
   __ mov(r2, Operand(0));
   __ GetBuiltinEntry(r3, Builtins::CALL_NON_FUNCTION);
   __ Jump(Handle<Code>(Builtins::builtin(Builtins::ArgumentsAdaptorTrampoline)),
           RelocInfo::CODE_TARGET);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal