Make CTX allocatable by the register allocator.

runtime/vm/stub_code_arm.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_ARM)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 27 matching lines @@
   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();
   const intptr_t exitframe_last_param_slot_from_fp = 2;
 
   __ mov(IP, Operand(0));
   __ Push(IP);  // Push 0 for the PC marker.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
 
-  __ LoadIsolate(R0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << R9)) != 0);
+  __ LoadIsolate(R9);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
-  __ StoreToOffset(kWord, SP, R0, Isolate::top_exit_frame_info_offset());
-
-  // Save current Context pointer into Isolate structure.
-  __ StoreToOffset(kWord, CTX, R0, Isolate::top_context_offset());
-
-  // Cache Isolate pointer into CTX while executing runtime code.
-  __ mov(CTX, Operand(R0));
+  __ StoreToOffset(kWord, SP, R9, Isolate::top_exit_frame_info_offset());
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ LoadFromOffset(kWord, R6, CTX, Isolate::vm_tag_offset());
+    __ LoadFromOffset(kWord, R6, R9, Isolate::vm_tag_offset());
     __ CompareImmediate(R6, VMTag::kDartTagId);
     __ b(&ok, EQ);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing VM code.
-  __ StoreToOffset(kWord, R5, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R5, R9, Isolate::vm_tag_offset());
 
   // Reserve space for arguments and align frame before entering C++ world.
   // NativeArguments are passed in registers.
   ASSERT(sizeof(NativeArguments) == 4 * kWordSize);
   __ ReserveAlignedFrameSpace(0);
 
   // Pass NativeArguments structure by value and call runtime.
   // Registers R0, R1, R2, and R3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: R0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(R0, Operand(R9));
 
   // There are no runtime calls to closures, so we do not need to set the tag
   // bits kClosureFunctionBit and kInstanceFunctionBit in argc_tag_.
   ASSERT(argc_tag_offset == 1 * kWordSize);
   __ mov(R1, Operand(R4));  // Set argc in NativeArguments.
 
   ASSERT(argv_offset == 2 * kWordSize);
   __ add(R2, FP, Operand(R4, LSL, 2));  // Compute argv.
   // Set argv in NativeArguments.
   __ AddImmediate(R2, exitframe_last_param_slot_from_fp * kWordSize);
 
   ASSERT(retval_offset == 3 * kWordSize);
   __ add(R3, R2, Operand(kWordSize));  // Retval is next to 1st argument.
 
   // Call runtime or redirection via simulator.
   __ blx(R5);
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(R2, VMTag::kDartTagId);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R2, R9, Isolate::vm_tag_offset());
 
   // Reset exit frame information in Isolate structure.
   __ LoadImmediate(R2, 0);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::top_exit_frame_info_offset());
-
-  // Load Context pointer from Isolate structure into R2.
-  __ LoadFromOffset(kWord, R2, CTX, Isolate::top_context_offset());
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadImmediate(R3, reinterpret_cast<intptr_t>(Object::null()));
-  __ StoreToOffset(kWord, R3, CTX, Isolate::top_context_offset());
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, Operand(R2));
+  __ StoreToOffset(kWord, R2, R9, Isolate::top_exit_frame_info_offset());
 
   __ LeaveFrame((1 << FP) | (1 << LR));
   // Adjust SP for the empty PC marker.
   __ AddImmediate(SP, kWordSize);
   __ Ret();
 }
 
 
 // Print the stop message.
 DEFINE_LEAF_RUNTIME_ENTRY(void, PrintStopMessage, 1, const char* message) {
@@ skipping 23 matching lines @@
 void StubCode::GenerateCallNativeCFunctionStub(Assembler* assembler) {
   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();
 
   __ mov(IP, Operand(0));
   __ Push(IP);  // Push 0 for the PC marker.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
 
-  __ LoadIsolate(R0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << R9)) != 0);
+  __ LoadIsolate(R9);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ StoreToOffset(kWord, SP, R0, Isolate::top_exit_frame_info_offset());
-
-  // Save current Context pointer into Isolate structure.
-  __ StoreToOffset(kWord, CTX, R0, Isolate::top_context_offset());
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ mov(CTX, Operand(R0));
+  __ StoreToOffset(kWord, SP, R9, Isolate::top_exit_frame_info_offset());
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ LoadFromOffset(kWord, R6, CTX, Isolate::vm_tag_offset());
+    __ LoadFromOffset(kWord, R6, R9, Isolate::vm_tag_offset());
     __ CompareImmediate(R6, VMTag::kDartTagId);
     __ b(&ok, EQ);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ StoreToOffset(kWord, R5, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R5, R9, Isolate::vm_tag_offset());
 
   // Reserve space for the native arguments structure passed on the stack (the
   // outgoing pointer parameter to the native arguments structure is passed in
   // R0) and align frame before entering the C++ world.
   __ ReserveAlignedFrameSpace(sizeof(NativeArguments));
 
   // Initialize NativeArguments structure and call native function.
   // Registers R0, R1, R2, and R3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: R0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(R0, Operand(R9));
 
   // There are no native calls to closures, so we do not need to set the tag
   // bits kClosureFunctionBit and kInstanceFunctionBit in argc_tag_.
   ASSERT(argc_tag_offset == 1 * kWordSize);
   // Set argc in NativeArguments: R1 already contains argc.
 
   ASSERT(argv_offset == 2 * kWordSize);
   // Set argv in NativeArguments: R2 already contains argv.
 
   ASSERT(retval_offset == 3 * kWordSize);
@@ skipping 12 matching lines @@
   entry = Simulator::RedirectExternalReference(
       entry, Simulator::kNativeCall, NativeEntry::kNumCallWrapperArguments);
   __ LoadImmediate(R2, entry);
   __ blx(R2);
 #else
   __ BranchLink(&NativeEntry::NativeCallWrapperLabel());
 #endif
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(R2, VMTag::kDartTagId);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R2, R9, Isolate::vm_tag_offset());
 
   // Reset exit frame information in Isolate structure.
   __ LoadImmediate(R2, 0);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::top_exit_frame_info_offset());
-
-  // Load Context pointer from Isolate structure into R2.
-  __ LoadFromOffset(kWord, R2, CTX, Isolate::top_context_offset());
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadImmediate(R3, reinterpret_cast<intptr_t>(Object::null()));
-  __ StoreToOffset(kWord, R3, CTX, Isolate::top_context_offset());
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, Operand(R2));
+  __ StoreToOffset(kWord, R2, R9, Isolate::top_exit_frame_info_offset());
 
   __ LeaveFrame((1 << FP) | (1 << LR));
   // Adjust SP for the empty PC marker.
   __ AddImmediate(SP, kWordSize);
   __ Ret();
 }
 
 
 // Input parameters:
 //   LR : return address.
 //   SP : address of return value.
 //   R5 : address of the native function to call.
 //   R2 : address of first argument in argument array.
 //   R1 : argc_tag including number of arguments and function kind.
 void StubCode::GenerateCallBootstrapCFunctionStub(Assembler* assembler) {
   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();
 
   __ mov(IP, Operand(0));
   __ Push(IP);  // Push 0 for the PC marker.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
 
-  __ LoadIsolate(R0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << R9)) != 0);
+  __ LoadIsolate(R9);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ StoreToOffset(kWord, SP, R0, Isolate::top_exit_frame_info_offset());
-
-  // Save current Context pointer into Isolate structure.
-  __ StoreToOffset(kWord, CTX, R0, Isolate::top_context_offset());
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ mov(CTX, Operand(R0));
+  __ StoreToOffset(kWord, SP, R9, Isolate::top_exit_frame_info_offset());
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ LoadFromOffset(kWord, R6, CTX, Isolate::vm_tag_offset());
+    __ LoadFromOffset(kWord, R6, R9, Isolate::vm_tag_offset());
     __ CompareImmediate(R6, VMTag::kDartTagId);
     __ b(&ok, EQ);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ StoreToOffset(kWord, R5, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R5, R9, Isolate::vm_tag_offset());
 
   // Reserve space for the native arguments structure passed on the stack (the
   // outgoing pointer parameter to the native arguments structure is passed in
   // R0) and align frame before entering the C++ world.
   __ ReserveAlignedFrameSpace(sizeof(NativeArguments));
 
   // Initialize NativeArguments structure and call native function.
   // Registers R0, R1, R2, and R3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: R0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(R0, Operand(R9));
 
   // There are no native calls to closures, so we do not need to set the tag
   // bits kClosureFunctionBit and kInstanceFunctionBit in argc_tag_.
   ASSERT(argc_tag_offset == 1 * kWordSize);
   // Set argc in NativeArguments: R1 already contains argc.
 
   ASSERT(argv_offset == 2 * kWordSize);
   // Set argv in NativeArguments: R2 already contains argv.
 
   ASSERT(retval_offset == 3 * kWordSize);
   __ add(R3, FP, Operand(3 * kWordSize));  // Set retval in NativeArgs.
 
   // Passing the structure by value as in runtime calls would require changing
   // Dart API for native functions.
   // For now, space is reserved on the stack and we pass a pointer to it.
   __ stm(IA, SP,  (1 << R0) | (1 << R1) | (1 << R2) | (1 << R3));
   __ mov(R0, Operand(SP));  // Pass the pointer to the NativeArguments.
 
   // Call native function or redirection via simulator.
   __ blx(R5);
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(R2, VMTag::kDartTagId);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R2, R9, Isolate::vm_tag_offset());
 
   // Reset exit frame information in Isolate structure.
   __ LoadImmediate(R2, 0);
-  __ StoreToOffset(kWord, R2, CTX, Isolate::top_exit_frame_info_offset());
-
-  // Load Context pointer from Isolate structure into R2.
-  __ LoadFromOffset(kWord, R2, CTX, Isolate::top_context_offset());
-
-  // Reset Context pointer in Isolate structure.
-  __ LoadImmediate(R3, reinterpret_cast<intptr_t>(Object::null()));
-  __ StoreToOffset(kWord, R3, CTX, Isolate::top_context_offset());
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, Operand(R2));
+  __ StoreToOffset(kWord, R2, R9, Isolate::top_exit_frame_info_offset());
 
   __ LeaveFrame((1 << FP) | (1 << LR));
   // Adjust SP for the empty PC marker.
   __ AddImmediate(SP, kWordSize);
   __ Ret();
 }
 
 
 // Input parameters:
 //   R4: arguments descriptor array.
@@ skipping 426 matching lines @@
 //   LR : points to return address.
 //   R0 : entrypoint of the Dart function to call.
 //   R1 : arguments descriptor array.
 //   R2 : arguments array.
 //   R3 : new context containing the current isolate pointer.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   // Save frame pointer coming in.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
 
   // Save new context and C++ ABI callee-saved registers.
-  __ PushList((1 << R3) | kAbiPreservedCpuRegs);
+  __ PushList(kAbiPreservedCpuRegs);
 
   const DRegister firstd = EvenDRegisterOf(kAbiFirstPreservedFpuReg);
   if (TargetCPUFeatures::vfp_supported()) {
     ASSERT(2 * kAbiPreservedFpuRegCount < 16);
     // Save FPU registers. 2 D registers per Q register.
     __ vstmd(DB_W, SP, firstd, 2 * kAbiPreservedFpuRegCount);
   } else {
     __ sub(SP, SP, Operand(kAbiPreservedFpuRegCount * kFpuRegisterSize));
   }
 
   // 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();
 
-  // 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.
-  __ ldr(CTX, Address(R3, VMHandles::kOffsetOfRawPtrInHandle));
-
   __ LoadIsolate(R8);
 
   // Save the current VMTag on the stack.
-  ASSERT(kSavedVMTagSlotFromEntryFp == -25);
   __ LoadFromOffset(kWord, R5, R8, Isolate::vm_tag_offset());
   __ Push(R5);
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(R5, VMTag::kDartTagId);
   __ StoreToOffset(kWord, R5, R8, Isolate::vm_tag_offset());
 
   // Save the top exit frame info. Use R5 as a temporary register.
   // StackFrameIterator reads the top exit frame info saved in this frame.
   __ LoadFromOffset(kWord, R5, R8, Isolate::top_exit_frame_info_offset());
   __ LoadImmediate(R6, 0);
   __ StoreToOffset(kWord, R6, R8, Isolate::top_exit_frame_info_offset());
 
-  // Save the old Context pointer. Use R4 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.
-  // EntryFrame::SavedContext reads the context saved in this frame.
-  __ LoadFromOffset(kWord, R4, R8, Isolate::top_context_offset());
-
-  // The constants kSavedContextSlotFromEntryFp and
   // kExitLinkSlotFromEntryFp must be kept in sync with the code below.
-  ASSERT(kExitLinkSlotFromEntryFp == -26);
-  ASSERT(kSavedContextSlotFromEntryFp == -27);
-  __ PushList((1 << R4) | (1 << R5));
+  ASSERT(kExitLinkSlotFromEntryFp == -25);
+  __ Push(R5);
 
   // Load arguments descriptor array into R4, which is passed to Dart code.
   __ ldr(R4, Address(R1, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load number of arguments into R5.
   __ ldr(R5, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(R5);
 
   // Compute address of 'arguments array' data area into R2.
   __ ldr(R2, Address(R2, VMHandles::kOffsetOfRawPtrInHandle));
@@ skipping 11 matching lines @@
   __ AddImmediate(R2, kWordSize);
   __ AddImmediate(R1, 1);
   __ cmp(R1, Operand(R5));
   __ b(&push_arguments, LT);
   __ Bind(&done_push_arguments);
 
   // Call the Dart code entrypoint.
   __ blx(R0);  // R4 is the arguments descriptor array.
 
   // Get rid of arguments pushed on the stack.
-  __ AddImmediate(SP, FP, kSavedContextSlotFromEntryFp * kWordSize);
+  __ AddImmediate(SP, FP, kExitLinkSlotFromEntryFp * kWordSize);
 
-  // Load Isolate pointer into CTX.
-  __ LoadIsolate(CTX);
+  __ LoadIsolate(R8);
 
-  // Restore the saved Context pointer into the Isolate structure.
-  // Uses R4 as a temporary register for this.
   // Restore the saved top exit frame info back into the Isolate structure.
   // Uses R5 as a temporary register for this.
-  __ PopList((1 << R4) | (1 << R5));
-  __ StoreToOffset(kWord, R4, CTX, Isolate::top_context_offset());
-  __ StoreToOffset(kWord, R5, CTX, Isolate::top_exit_frame_info_offset());
+  __ Pop(R5);
+  __ StoreToOffset(kWord, R5, R8, Isolate::top_exit_frame_info_offset());
 
   // Restore the current VMTag from the stack.
   __ Pop(R4);
-  __ StoreToOffset(kWord, R4, CTX, Isolate::vm_tag_offset());
+  __ StoreToOffset(kWord, R4, R8, Isolate::vm_tag_offset());
 
   // Restore C++ ABI callee-saved registers.
   if (TargetCPUFeatures::vfp_supported()) {
     // Restore FPU registers. 2 D registers per Q register.
     __ vldmd(IA_W, SP, firstd, 2 * kAbiPreservedFpuRegCount);
   } else {
     __ AddImmediate(SP, kAbiPreservedFpuRegCount * kFpuRegisterSize);
   }
   // Restore CPU registers.
-  __ PopList((1 << R3) | kAbiPreservedCpuRegs);  // Ignore restored R3.
+  __ PopList(kAbiPreservedCpuRegs);
 
   // Restore the frame pointer and return.
   __ LeaveFrame((1 << FP) | (1 << LR));
   __ Ret();
 }
 
 
 // Called for inline allocation of contexts.
 // Input:
 //   R1: number of context variables.
@@ skipping 1143 matching lines @@
   const Register right = R0;
   __ ldr(left, Address(SP, 1 * kWordSize));
   __ ldr(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM