Make CTX allocatable by the register allocator.

runtime/vm/stub_code_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 18 matching lines @@
 
 // Input parameters:
 //   RSP : points to return address.
 //   RSP + 8 : address of last argument in argument array.
 //   RSP + 8*R10 : address of first argument in argument array.
 //   RSP + 8*R10 + 8 : address of return value.
 //   RBX : address of the runtime function to call.
 //   R10 : number of arguments to the call.
 // Must preserve callee saved registers R12 and R13.
 void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
-  ASSERT((R12 != CTX) && (R13 != CTX));
   const intptr_t isolate_offset = NativeArguments::isolate_offset();
   const intptr_t argc_tag_offset = NativeArguments::argc_tag_offset();
   const intptr_t argv_offset = NativeArguments::argv_offset();
   const intptr_t retval_offset = NativeArguments::retval_offset();
 
   __ EnterFrame(0);
 
-  __ LoadIsolate(RAX);
+  COMPILE_ASSERT(
+      (CallingConventions::kCalleeSaveCpuRegisters & (1 << R12)) != 0);
+  __ LoadIsolate(R12);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
-  __ movq(Address(RAX, Isolate::top_exit_frame_info_offset()), RSP);
-
-  // Save current Context pointer into Isolate structure.
-  __ movq(Address(RAX, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing runtime code.
-  __ movq(CTX, RAX);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), RSP);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movq(RAX, Immediate(VMTag::kDartTagId));
-    __ cmpq(RAX, Address(CTX, Isolate::vm_tag_offset()));
+    __ cmpq(RAX, Address(R12, Isolate::vm_tag_offset()));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing VM code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()), RBX);
+  __ movq(Address(R12, Isolate::vm_tag_offset()), RBX);
 
   // Reserve space for arguments and align frame before entering C++ world.
   __ subq(RSP, Immediate(sizeof(NativeArguments)));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andq(RSP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call runtime.
-  __ movq(Address(RSP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movq(Address(RSP, isolate_offset), R12);  // Set isolate in NativeArgs.
   // There are no runtime calls to closures, so we do not need to set the tag
   // bits kClosureFunctionBit and kInstanceFunctionBit in argc_tag_.
   __ movq(Address(RSP, argc_tag_offset), R10);  // Set argc in NativeArguments.
   __ leaq(RAX, Address(RBP, R10, TIMES_8, 1 * kWordSize));  // Compute argv.
   __ movq(Address(RSP, argv_offset), RAX);  // Set argv in NativeArguments.
   __ addq(RAX, Immediate(1 * kWordSize));  // Retval is next to 1st argument.
   __ movq(Address(RSP, retval_offset), RAX);  // Set retval in NativeArguments.
 #if defined(_WIN64)
   ASSERT(sizeof(NativeArguments) > CallingConventions::kRegisterTransferLimit);
   __ movq(CallingConventions::kArg1Reg, RSP);
 #endif
   __ CallCFunction(RBX);
 
   // Mark that the isolate is executing Dart code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()),
+  __ movq(Address(R12, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movq(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into RBX.
-  __ movq(RBX, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadObject(R12, Object::null_object(), PP);
-  __ movq(Address(CTX, Isolate::top_context_offset()), R12);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movq(CTX, RBX);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
   __ LeaveFrame();
   __ ret();
 }
 
 
 // Print the stop message.
 DEFINE_LEAF_RUNTIME_ENTRY(void, PrintStopMessage, 1, const char* message) {
   OS::Print("Stop message: %s\n", message);
 }
@@ skipping 28 matching lines @@
       NativeArguments::isolate_offset() + native_args_struct_offset;
   const intptr_t argc_tag_offset =
       NativeArguments::argc_tag_offset() + native_args_struct_offset;
   const intptr_t argv_offset =
       NativeArguments::argv_offset() + native_args_struct_offset;
   const intptr_t retval_offset =
       NativeArguments::retval_offset() + native_args_struct_offset;
 
   __ EnterFrame(0);
 
-  __ LoadIsolate(R8);
+  COMPILE_ASSERT(
+      (CallingConventions::kCalleeSaveCpuRegisters & (1 << R12)) != 0);
+  __ LoadIsolate(R12);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ movq(Address(R8, Isolate::top_exit_frame_info_offset()), RSP);
-
-// Save current Context pointer into Isolate structure.
-  __ movq(Address(R8, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ movq(CTX, R8);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), RSP);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movq(R8, Immediate(VMTag::kDartTagId));
-    __ cmpq(R8, Address(CTX, Isolate::vm_tag_offset()));
+    __ cmpq(R8, Address(R12, Isolate::vm_tag_offset()));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()), RBX);
+  __ movq(Address(R12, Isolate::vm_tag_offset()), RBX);
 
   // Reserve space for the native arguments structure passed on the stack (the
   // outgoing pointer parameter to the native arguments structure is passed in
   // RDI) and align frame before entering the C++ world.
   __ subq(RSP, Immediate(sizeof(NativeArguments)));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andq(RSP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call native function.
-  __ movq(Address(RSP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movq(Address(RSP, isolate_offset), R12);  // Set isolate in NativeArgs.
   __ movq(Address(RSP, argc_tag_offset), R10);  // Set argc in NativeArguments.
   __ movq(Address(RSP, argv_offset), RAX);  // Set argv in NativeArguments.
   __ leaq(RAX, Address(RBP, 2 * kWordSize));  // Compute return value addr.
   __ movq(Address(RSP, retval_offset), RAX);  // Set retval in NativeArguments.
 
   // Pass the pointer to the NativeArguments.
   __ movq(CallingConventions::kArg1Reg, RSP);
   // Pass pointer to function entrypoint.
   __ movq(CallingConventions::kArg2Reg, RBX);
   __ CallCFunction(&NativeEntry::NativeCallWrapperLabel());
 
   // Mark that the isolate is executing Dart code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()),
+  __ movq(Address(R12, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movq(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into R8.
-  __ movq(R8, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadObject(R12, Object::null_object(), PP);
-  __ movq(Address(CTX, Isolate::top_context_offset()), R12);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movq(CTX, R8);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
   __ LeaveFrame();
   __ ret();
 }
 
 
 // Input parameters:
 //   RSP : points to return address.
 //   RSP + 8 : address of return value.
 //   RAX : address of first argument in argument array.
 //   RBX : address of the native function to call.
 //   R10 : argc_tag including number of arguments and function kind.
 void StubCode::GenerateCallBootstrapCFunctionStub(Assembler* assembler) {
   const intptr_t native_args_struct_offset = 0;
   const intptr_t isolate_offset =
       NativeArguments::isolate_offset() + native_args_struct_offset;
   const intptr_t argc_tag_offset =
       NativeArguments::argc_tag_offset() + native_args_struct_offset;
   const intptr_t argv_offset =
       NativeArguments::argv_offset() + native_args_struct_offset;
   const intptr_t retval_offset =
       NativeArguments::retval_offset() + native_args_struct_offset;
 
   __ EnterFrame(0);
 
-  __ LoadIsolate(R8);
+  COMPILE_ASSERT(
+      (CallingConventions::kCalleeSaveCpuRegisters & (1 << R12)) != 0);
+  __ LoadIsolate(R12);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ movq(Address(R8, Isolate::top_exit_frame_info_offset()), RSP);
-
-  // Save current Context pointer into Isolate structure.
-  __ movq(Address(R8, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ movq(CTX, R8);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), RSP);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movq(R8, Immediate(VMTag::kDartTagId));
-    __ cmpq(R8, Address(CTX, Isolate::vm_tag_offset()));
+    __ cmpq(R8, Address(R12, Isolate::vm_tag_offset()));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()), RBX);
+  __ movq(Address(R12, Isolate::vm_tag_offset()), RBX);
 
   // Reserve space for the native arguments structure passed on the stack (the
   // outgoing pointer parameter to the native arguments structure is passed in
   // RDI) and align frame before entering the C++ world.
   __ subq(RSP, Immediate(sizeof(NativeArguments)));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andq(RSP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call native function.
-  __ movq(Address(RSP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movq(Address(RSP, isolate_offset), R12);  // Set isolate in NativeArgs.
   __ movq(Address(RSP, argc_tag_offset), R10);  // Set argc in NativeArguments.
   __ movq(Address(RSP, argv_offset), RAX);  // Set argv in NativeArguments.
   __ leaq(RAX, Address(RBP, 2 * kWordSize));  // Compute return value addr.
   __ movq(Address(RSP, retval_offset), RAX);  // Set retval in NativeArguments.
 
   // Pass the pointer to the NativeArguments.
   __ movq(CallingConventions::kArg1Reg, RSP);
   __ CallCFunction(RBX);
 
   // Mark that the isolate is executing Dart code.
-  __ movq(Address(CTX, Isolate::vm_tag_offset()),
+  __ movq(Address(R12, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movq(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into R8.
-  __ movq(R8, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadObject(R12, Object::null_object(), PP);
-  __ movq(Address(CTX, Isolate::top_context_offset()), R12);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movq(CTX, R8);
+  __ movq(Address(R12, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
   __ LeaveFrame();
   __ ret();
 }
 
 
 // Input parameters:
 //   R10: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
   __ EnterStubFrame();
@@ skipping 413 matching lines @@
 //   RSI : arguments descriptor array.
 //   RDX : arguments array.
 //   RCX : new context containing the current isolate pointer.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   // Save frame pointer coming in.
   __ EnterFrame(0);
 
   const Register kEntryPointReg = CallingConventions::kArg1Reg;
   const Register kArgDescReg    = CallingConventions::kArg2Reg;
   const Register kArgsReg       = CallingConventions::kArg3Reg;
-  const Register kNewContextReg = CallingConventions::kArg4Reg;
 
   // At this point, the stack looks like:
   // | saved RBP                                      | <-- RBP
   // | saved PC (return to DartEntry::InvokeFunction) |
 
   const intptr_t kInitialOffset = 1;
-  // Save arguments descriptor array and new context.
+  // Save arguments descriptor array.
   const intptr_t kArgumentsDescOffset = -(kInitialOffset) * kWordSize;
   __ pushq(kArgDescReg);
-  __ pushq(kNewContextReg);
 
   // Save C++ ABI callee-saved registers.
   __ PushRegisters(CallingConventions::kCalleeSaveCpuRegisters,
                    CallingConventions::kCalleeSaveXmmRegisters);
 
   // We now load the pool pointer(PP) as we are about to invoke dart code and we
   // could potentially invoke some intrinsic functions which need the PP to be
   // set up.
   __ LoadPoolPointer(PP);
 
   // If any additional (or fewer) values are pushed, the offsets in
-  // kExitLinkSlotFromEntryFp and kSavedContextSlotFromEntryFp will need to be
-  // changed.
-
-  // The new Context structure contains a pointer to the current Isolate
-  // structure. Cache the Context pointer in the CTX register so that it is
-  // available in generated code and calls to Isolate::Current() need not be
-  // done. The assumption is that this register will never be clobbered by
-  // compiled or runtime stub code.
-
-  // Cache the new Context pointer into CTX while executing Dart code.
-  __ movq(CTX, Address(kNewContextReg, VMHandles::kOffsetOfRawPtrInHandle));
-
-  const Register kIsolateReg = RBX;
+  // kExitLinkSlotFromEntryFp will need to be changed.
 
   // Load Isolate pointer into kIsolateReg.
+  const Register kIsolateReg = RBX;
   __ LoadIsolate(kIsolateReg);
 
   // Save the current VMTag on the stack.
   __ movq(RAX, Address(kIsolateReg, Isolate::vm_tag_offset()));
   __ pushq(RAX);
-#if defined(DEBUG)
-  {
-    Label ok;
-    __ leaq(RAX, Address(RBP, kSavedVMTagSlotFromEntryFp * kWordSize));
-    __ cmpq(RAX, RSP);
-    __ j(EQUAL, &ok);
-    __ Stop("kSavedVMTagSlotFromEntryFp mismatch");
-    __ Bind(&ok);
-  }
-#endif
 
   // Mark that the isolate is executing Dart code.
   __ movq(Address(kIsolateReg, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Save the top exit frame info. Use RAX as a temporary register.
   // StackFrameIterator reads the top exit frame info saved in this frame.
   // The constant kExitLinkSlotFromEntryFp must be kept in sync with the
   // code below.
   __ movq(RAX, Address(kIsolateReg, Isolate::top_exit_frame_info_offset()));
   __ pushq(RAX);
 #if defined(DEBUG)
   {
     Label ok;
     __ leaq(RAX, Address(RBP, kExitLinkSlotFromEntryFp * kWordSize));
     __ cmpq(RAX, RSP);
     __ j(EQUAL, &ok);
     __ Stop("kExitLinkSlotFromEntryFp mismatch");
     __ Bind(&ok);
   }
 #endif
 
   __ movq(Address(kIsolateReg, Isolate::top_exit_frame_info_offset()),
           Immediate(0));
 
-  // Save the old Context pointer. Use RAX as a temporary register.
-  // Note that VisitObjectPointers will find this saved Context pointer during
-  // GC marking, since it traverses any information between SP and
-  // FP - kExitLinkSlotFromEntryFp * kWordSize.
-  // EntryFrame::SavedContext reads the context saved in this frame.
-  // The constant kSavedContextSlotFromEntryFp must be kept in sync with
-  // the code below.
-  __ movq(RAX, Address(kIsolateReg, Isolate::top_context_offset()));
-  __ pushq(RAX);
-#if defined(DEBUG)
-  {
-    Label ok;
-    __ leaq(RAX, Address(RBP, kSavedContextSlotFromEntryFp * kWordSize));
-    __ cmpq(RAX, RSP);
-    __ j(EQUAL, &ok);
-    __ Stop("kSavedContextSlotFromEntryFp mismatch");
-    __ Bind(&ok);
-  }
-#endif
-
   // Load arguments descriptor array into R10, which is passed to Dart code.
   __ movq(R10, Address(kArgDescReg, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Push arguments. At this point we only need to preserve kEntryPointReg.
   ASSERT(kEntryPointReg != RDX);
 
   // Load number of arguments into RBX.
   __ movq(RBX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(RBX);
 
@@ skipping 18 matching lines @@
   __ call(kEntryPointReg);  // R10 is the arguments descriptor array.
 
   // Read the saved arguments descriptor array to obtain the number of passed
   // arguments.
   __ movq(kArgDescReg, Address(RBP, kArgumentsDescOffset));
   __ movq(R10, Address(kArgDescReg, VMHandles::kOffsetOfRawPtrInHandle));
   __ movq(RDX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   // Get rid of arguments pushed on the stack.
   __ leaq(RSP, Address(RSP, RDX, TIMES_4, 0));  // RDX is a Smi.
 
+  // Restore the saved top exit frame info back into the Isolate structure.
   __ LoadIsolate(kIsolateReg);
-  // Restore the saved Context pointer into the Isolate structure.
-  __ popq(Address(kIsolateReg, Isolate::top_context_offset()));
-
-  // Restore the saved top exit frame info back into the Isolate structure.
   __ popq(Address(kIsolateReg, Isolate::top_exit_frame_info_offset()));
 
   // Restore the current VMTag from the stack.
   __ popq(Address(kIsolateReg, Isolate::vm_tag_offset()));
 
   // Restore C++ ABI callee-saved registers.
   __ PopRegisters(CallingConventions::kCalleeSaveCpuRegisters,
                   CallingConventions::kCalleeSaveXmmRegisters);
 
   // Restore the frame pointer.
@@ skipping 1150 matching lines @@
 
   __ movq(left, Address(RSP, 2 * kWordSize));
   __ movq(right, Address(RSP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64