Out-of-line constant pool on Arm: Stage 1 - Free up r7 for use as constant pool pointer register

src/arm/macro-assembler-arm.cc

 // Copyright 2012 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 1312 matching lines @@
 void MacroAssembler::PushTryHandler(StackHandler::Kind kind,
                                     int handler_index) {
   // Adjust this code if not the case.
   STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kCodeOffset == 1 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kStateOffset == 2 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kContextOffset == 3 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kFPOffset == 4 * kPointerSize);
 
-  // For the JSEntry handler, we must preserve r0-r4, r5-r7 are available.
+  // For the JSEntry handler, we must preserve r0-r4, r5-r6 are available.
   // We will build up the handler from the bottom by pushing on the stack.
   // Set up the code object (r5) and the state (r6) for pushing.
   unsigned state =
       StackHandler::IndexField::encode(handler_index) |
       StackHandler::KindField::encode(kind);
   mov(r5, Operand(CodeObject()));
   mov(r6, Operand(state));
 
   // Push the frame pointer, context, state, and code object.
   if (kind == StackHandler::JS_ENTRY) {
-    mov(r7, Operand(Smi::FromInt(0)));  // Indicates no context.
+    mov(cp, Operand(Smi::FromInt(0)));  // Indicates no context.

[Rodolph Perfetta, 2013/09/13 14:14:40]

I don't know if this is related to your test flakyness, but here I don't believe
you can corrupt the context pointer. Look in full-codegen-arm.cc when
PushTryHandler is used

[ulan, 2013/09/13 14:20:48]

I also had this suspicion, but this case seems to be fine because PushTryHandler
with kind = JS_ENTRY is called only in JSEntryStub::GenerateBody and cp is later
overwrite in JSEntryTrampoline.

     mov(ip, Operand::Zero());  // NULL frame pointer.
-    stm(db_w, sp, r5.bit() | r6.bit() | r7.bit() | ip.bit());
+    stm(db_w, sp, r5.bit() | r6.bit() | cp.bit() | ip.bit());
   } else {
     stm(db_w, sp, r5.bit() | r6.bit() | cp.bit() | fp.bit());
   }
 
   // Link the current handler as the next handler.
   mov(r6, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
   ldr(r5, MemOperand(r6));
   push(r5);
   // Set this new handler as the current one.
   str(sp, MemOperand(r6));
@@ skipping 932 matching lines @@
   ExternalReference next_address =
       ExternalReference::handle_scope_next_address(isolate());
   const int kNextOffset = 0;
   const int kLimitOffset = AddressOffset(
       ExternalReference::handle_scope_limit_address(isolate()),
       next_address);
   const int kLevelOffset = AddressOffset(
       ExternalReference::handle_scope_level_address(isolate()),
       next_address);
 
+  ASSERT(!thunk_last_arg.is(r3));
+
   // Allocate HandleScope in callee-save registers.
-  mov(r7, Operand(next_address));
-  ldr(r4, MemOperand(r7, kNextOffset));
-  ldr(r5, MemOperand(r7, kLimitOffset));
-  ldr(r6, MemOperand(r7, kLevelOffset));
+  mov(r9, Operand(next_address));
+  ldr(r4, MemOperand(r9, kNextOffset));
+  ldr(r5, MemOperand(r9, kLimitOffset));
+  ldr(r6, MemOperand(r9, kLevelOffset));
   add(r6, r6, Operand(1));
-  str(r6, MemOperand(r7, kLevelOffset));
+  str(r6, MemOperand(r9, kLevelOffset));
 
   if (FLAG_log_timer_events) {
     FrameScope frame(this, StackFrame::MANUAL);
     PushSafepointRegisters();
     PrepareCallCFunction(1, r0);
     mov(r0, Operand(ExternalReference::isolate_address(isolate())));
     CallCFunction(ExternalReference::log_enter_external_function(isolate()), 1);
     PopSafepointRegisters();
   }
 
-  ASSERT(!thunk_last_arg.is(r3));
   Label profiler_disabled;
   Label end_profiler_check;
   bool* is_profiling_flag =
       isolate()->cpu_profiler()->is_profiling_address();
   STATIC_ASSERT(sizeof(*is_profiling_flag) == 1);
   mov(r3, Operand(reinterpret_cast<int32_t>(is_profiling_flag)));
   ldrb(r3, MemOperand(r3, 0));
   cmp(r3, Operand(0));
   b(eq, &profiler_disabled);
 
@@ skipping 24 matching lines @@
   Label promote_scheduled_exception;
   Label delete_allocated_handles;
   Label leave_exit_frame;
   Label return_value_loaded;
 
   // load value from ReturnValue
   ldr(r0, MemOperand(fp, return_value_offset*kPointerSize));
   bind(&return_value_loaded);
   // No more valid handles (the result handle was the last one). Restore
   // previous handle scope.
-  str(r4, MemOperand(r7, kNextOffset));
+  str(r4, MemOperand(r9, kNextOffset));
   if (emit_debug_code()) {
-    ldr(r1, MemOperand(r7, kLevelOffset));
+    ldr(r1, MemOperand(r9, kLevelOffset));
     cmp(r1, r6);
     Check(eq, kUnexpectedLevelAfterReturnFromApiCall);
   }
   sub(r6, r6, Operand(1));
-  str(r6, MemOperand(r7, kLevelOffset));
-  ldr(ip, MemOperand(r7, kLimitOffset));
+  str(r6, MemOperand(r9, kLevelOffset));
+  ldr(ip, MemOperand(r9, kLimitOffset));
   cmp(r5, ip);
   b(ne, &delete_allocated_handles);
 
   // Check if the function scheduled an exception.
   bind(&leave_exit_frame);
   LoadRoot(r4, Heap::kTheHoleValueRootIndex);
   mov(ip, Operand(ExternalReference::scheduled_exception_address(isolate())));
   ldr(r5, MemOperand(ip));
   cmp(r4, r5);
   b(ne, &promote_scheduled_exception);
 
   // LeaveExitFrame expects unwind space to be in a register.
   mov(r4, Operand(stack_space));
   LeaveExitFrame(false, r4);
   mov(pc, lr);
 
   bind(&promote_scheduled_exception);
   TailCallExternalReference(
       ExternalReference(Runtime::kPromoteScheduledException, isolate()),
       0,
       1);
 
   // HandleScope limit has changed. Delete allocated extensions.
   bind(&delete_allocated_handles);
-  str(r5, MemOperand(r7, kLimitOffset));
+  str(r5, MemOperand(r9, kLimitOffset));
   mov(r4, r0);
   PrepareCallCFunction(1, r5);
   mov(r0, Operand(ExternalReference::isolate_address(isolate())));
   CallCFunction(
       ExternalReference::delete_handle_scope_extensions(isolate()), 1);
   mov(r0, r4);
   jmp(&leave_exit_frame);
 }
 
 
@@ skipping 1479 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM