Make CTX allocatable by the register allocator.

runtime/vm/stub_code_mips.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_MIPS)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 30 matching lines @@
   const intptr_t exitframe_last_param_slot_from_fp = 2;
 
   __ SetPrologueOffset();
   __ TraceSimMsg("CallToRuntimeStub");
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
   __ sw(ZR, Address(SP, 2 * kWordSize));  // Push 0 for the PC marker
   __ sw(RA, Address(SP, 1 * kWordSize));
   __ sw(FP, Address(SP, 0 * kWordSize));
   __ mov(FP, SP);
 
-  __ LoadIsolate(A0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << S6)) != 0);
+  __ LoadIsolate(S6);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
-  __ sw(SP, Address(A0, Isolate::top_exit_frame_info_offset()));
-
-  // Save current Context pointer into Isolate structure.
-  __ sw(CTX, Address(A0, Isolate::top_context_offset()));
-
-  // Cache Isolate pointer into CTX while executing runtime code.
-  __ mov(CTX, A0);
+  __ sw(SP, Address(S6, Isolate::top_exit_frame_info_offset()));
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ lw(T0, Address(A0, Isolate::vm_tag_offset()));
+    __ lw(T0, Address(S6, Isolate::vm_tag_offset()));
     __ BranchEqual(T0, Immediate(VMTag::kDartTagId), &ok);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing VM code.
-  __ sw(S5, Address(A0, Isolate::vm_tag_offset()));
+  __ sw(S5, Address(S6, 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(4 * kWordSize);  // Reserve space for arguments.
 
   // Pass NativeArguments structure by value and call runtime.
   // Registers A0, A1, A2, and A3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: A0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(A0, S6);
 
   // 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(A1, S4);  // Set argc in NativeArguments.
 
   ASSERT(argv_offset == 2 * kWordSize);
   __ sll(A2, S4, 2);
   __ addu(A2, FP, A2);  // Compute argv.
   // Set argv in NativeArguments.
   __ addiu(A2, A2, Immediate(exitframe_last_param_slot_from_fp * kWordSize));
 
 
   // Call runtime or redirection via simulator.
   // We defensively always jalr through T9 because it is sometimes required by
   // the MIPS ABI.
   __ mov(T9, S5);
   __ jalr(T9);
 
     ASSERT(retval_offset == 3 * kWordSize);
   // Retval is next to 1st argument.
   __ delay_slot()->addiu(A3, A2, Immediate(kWordSize));
   __ TraceSimMsg("CallToRuntimeStub return");
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(A2, VMTag::kDartTagId);
-  __ sw(A2, Address(CTX, Isolate::vm_tag_offset()));
+  __ sw(A2, Address(S6, Isolate::vm_tag_offset()));
 
   // Reset exit frame information in Isolate structure.
-  __ sw(ZR, Address(CTX, Isolate::top_exit_frame_info_offset()));
-
-  // Load Context pointer from Isolate structure into A2.
-  __ lw(A2, Address(CTX, Isolate::top_context_offset()));
-
-  // Load null.
-  __ LoadImmediate(TMP, reinterpret_cast<intptr_t>(Object::null()));
-
-  // Reset Context pointer in Isolate structure.
-  __ sw(TMP, Address(CTX, Isolate::top_context_offset()));
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, A2);
+  __ sw(ZR, Address(S6, Isolate::top_exit_frame_info_offset()));
 
   __ mov(SP, FP);
   __ lw(RA, Address(SP, 1 * kWordSize));
   __ lw(FP, Address(SP, 0 * kWordSize));
   __ Ret();
   __ delay_slot()->addiu(SP, SP, Immediate(3 * kWordSize));
 }
 
 
 // Print the stop message.
@@ skipping 28 matching lines @@
   const intptr_t retval_offset = NativeArguments::retval_offset();
 
   __ SetPrologueOffset();
   __ TraceSimMsg("CallNativeCFunctionStub");
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
   __ sw(ZR, Address(SP, 2 * kWordSize));  // Push 0 for the PC marker
   __ sw(RA, Address(SP, 1 * kWordSize));
   __ sw(FP, Address(SP, 0 * kWordSize));
   __ mov(FP, SP);
 
-  __ LoadIsolate(A0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << S6)) != 0);
+  __ LoadIsolate(S6);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ sw(SP, Address(A0, Isolate::top_exit_frame_info_offset()));
-
-  // Save current Context pointer into Isolate structure.
-  __ sw(CTX, Address(A0, Isolate::top_context_offset()));
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ mov(CTX, A0);
+  __ sw(SP, Address(S6, Isolate::top_exit_frame_info_offset()));
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ lw(T0, Address(A0, Isolate::vm_tag_offset()));
+    __ lw(T0, Address(S6, Isolate::vm_tag_offset()));
     __ BranchEqual(T0, Immediate(VMTag::kDartTagId), &ok);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ sw(T5, Address(A0, Isolate::vm_tag_offset()));
+  __ sw(T5, Address(S6, Isolate::vm_tag_offset()));
 
   // Initialize NativeArguments structure and call native function.
   // Registers A0, A1, A2, and A3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: A0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(A0, S6);
 
   // 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: A1 already contains argc.
 
   ASSERT(argv_offset == 2 * kWordSize);
   // Set argv in NativeArguments: A2 already contains argv.
 
   ASSERT(retval_offset == 3 * kWordSize);
@@ skipping 19 matching lines @@
       entry, Simulator::kNativeCall, NativeEntry::kNumCallWrapperArguments);
   __ LoadImmediate(T9, entry);
   __ jalr(T9);
 #else
   __ BranchLink(&NativeEntry::NativeCallWrapperLabel());
 #endif
   __ TraceSimMsg("CallNativeCFunctionStub return");
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(A2, VMTag::kDartTagId);
-  __ sw(A2, Address(CTX, Isolate::vm_tag_offset()));
+  __ sw(A2, Address(S6, Isolate::vm_tag_offset()));
 
   // Reset exit frame information in Isolate structure.
-  __ sw(ZR, Address(CTX, Isolate::top_exit_frame_info_offset()));
-
-  // Load Context pointer from Isolate structure into A2.
-  __ lw(A2, Address(CTX, Isolate::top_context_offset()));
-
-  // Load null.
-  __ LoadImmediate(TMP, reinterpret_cast<intptr_t>(Object::null()));
-
-  // Reset Context pointer in Isolate structure.
-  __ sw(TMP, Address(CTX, Isolate::top_context_offset()));
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, A2);
+  __ sw(ZR, Address(S6, Isolate::top_exit_frame_info_offset()));
 
   __ mov(SP, FP);
   __ lw(RA, Address(SP, 1 * kWordSize));
   __ lw(FP, Address(SP, 0 * kWordSize));
   __ Ret();
   __ delay_slot()->addiu(SP, SP, Immediate(3 * kWordSize));
 }
 
 
 // Input parameters:
 //   RA : return address.
 //   SP : address of return value.
 //   T5 : address of the native function to call.
 //   A2 : address of first argument in argument array.
 //   A1 : 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();
 
   __ SetPrologueOffset();
   __ TraceSimMsg("CallNativeCFunctionStub");
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
   __ sw(ZR, Address(SP, 2 * kWordSize));  // Push 0 for the PC marker
   __ sw(RA, Address(SP, 1 * kWordSize));
   __ sw(FP, Address(SP, 0 * kWordSize));
   __ mov(FP, SP);
 
-  __ LoadIsolate(A0);
+  COMPILE_ASSERT((kAbiPreservedCpuRegs & (1 << S6)) != 0);
+  __ LoadIsolate(S6);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to native code.
-  __ sw(SP, Address(A0, Isolate::top_exit_frame_info_offset()));
-
-  // Save current Context pointer into Isolate structure.
-  __ sw(CTX, Address(A0, Isolate::top_context_offset()));
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ mov(CTX, A0);
+  __ sw(SP, Address(S6, Isolate::top_exit_frame_info_offset()));
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ lw(T0, Address(A0, Isolate::vm_tag_offset()));
+    __ lw(T0, Address(S6, Isolate::vm_tag_offset()));
     __ BranchEqual(T0, Immediate(VMTag::kDartTagId), &ok);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ sw(T5, Address(A0, Isolate::vm_tag_offset()));
+  __ sw(T5, Address(S6, Isolate::vm_tag_offset()));
 
   // Initialize NativeArguments structure and call native function.
   // Registers A0, A1, A2, and A3 are used.
 
   ASSERT(isolate_offset == 0 * kWordSize);
-  // Set isolate in NativeArgs: A0 already contains CTX.
+  // Set isolate in NativeArgs.
+  __ mov(A0, S6);
 
   // 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: A1 already contains argc.
 
   ASSERT(argv_offset == 2 * kWordSize);
   // Set argv in NativeArguments: A2 already contains argv.
 
   ASSERT(retval_offset == 3 * kWordSize);
@@ skipping 14 matching lines @@
   // Call native function or redirection via simulator.
 
   // We defensively always jalr through T9 because it is sometimes required by
   // the MIPS ABI.
   __ mov(T9, T5);
   __ jalr(T9);
   __ TraceSimMsg("CallNativeCFunctionStub return");
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(A2, VMTag::kDartTagId);
-  __ sw(A2, Address(CTX, Isolate::vm_tag_offset()));
+  __ sw(A2, Address(S6, Isolate::vm_tag_offset()));
 
   // Reset exit frame information in Isolate structure.
-  __ sw(ZR, Address(CTX, Isolate::top_exit_frame_info_offset()));
-
-  // Load Context pointer from Isolate structure into A2.
-  __ lw(A2, Address(CTX, Isolate::top_context_offset()));
-
-  // Load null.
-  __ LoadImmediate(TMP, reinterpret_cast<intptr_t>(Object::null()));
-
-  // Reset Context pointer in Isolate structure.
-  __ sw(TMP, Address(CTX, Isolate::top_context_offset()));
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ mov(CTX, A2);
+  __ sw(ZR, Address(S6, Isolate::top_exit_frame_info_offset()));
 
   __ mov(SP, FP);
   __ lw(RA, Address(SP, 1 * kWordSize));
   __ lw(FP, Address(SP, 0 * kWordSize));
   __ Ret();
   __ delay_slot()->addiu(SP, SP, Immediate(3 * kWordSize));
 }
 
 
 // Input parameters:
@@ skipping 473 matching lines @@
   __ BranchPatchable(&stub_code->FixAllocateArrayStubTargetLabel());
 }
 
 
 // Called when invoking Dart code from C++ (VM code).
 // Input parameters:
 //   RA : points to return address.
 //   A0 : entrypoint of the Dart function to call.
 //   A1 : arguments descriptor array.
 //   A2 : arguments array.
-//   A3 : new context containing the current isolate pointer.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   // Save frame pointer coming in.
   __ TraceSimMsg("InvokeDartCodeStub");
   __ EnterFrame();
 
   // Save new context and C++ ABI callee-saved registers.
 
-  // The new context, saved vm tag, the top exit frame, and the old context.
-  const intptr_t kPreservedContextSlots = 4;
+  // The saved vm tag and the top exit frame.
+  const intptr_t kPreservedSlots = 2;
   const intptr_t kPreservedRegSpace =
       kWordSize * (kAbiPreservedCpuRegCount + kAbiPreservedFpuRegCount +
-                   kPreservedContextSlots);
+                   kPreservedSlots);
 
   __ addiu(SP, SP, Immediate(-kPreservedRegSpace));
   for (int i = S0; i <= S7; i++) {
     Register r = static_cast<Register>(i);
-    const intptr_t slot = i - S0 + kPreservedContextSlots;
+    const intptr_t slot = i - S0 + kPreservedSlots;
     __ sw(r, Address(SP, slot * kWordSize));
   }
 
   for (intptr_t i = kAbiFirstPreservedFpuReg;
        i <= kAbiLastPreservedFpuReg; i++) {
     FRegister r = static_cast<FRegister>(i);
     const intptr_t slot =
-        kAbiPreservedCpuRegCount + kPreservedContextSlots + i -
+        kAbiPreservedCpuRegCount + kPreservedSlots + i -
         kAbiFirstPreservedFpuReg;
     __ swc1(r, Address(SP, slot * kWordSize));
   }
 
-  __ sw(A3, Address(SP, 3 * kWordSize));
-
   // 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.
-  __ lw(CTX, Address(A3, VMHandles::kOffsetOfRawPtrInHandle));
-
   __ LoadIsolate(T2);
 
   // Save the current VMTag on the stack.
-  ASSERT(kSavedVMTagSlotFromEntryFp == -22);
   __ lw(T1, Address(T2, Isolate::vm_tag_offset()));
-  __ sw(T1, Address(SP, 2 * kWordSize));
+  __ sw(T1, Address(SP, 1 * kWordSize));
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(T0, VMTag::kDartTagId);
   __ sw(T0, Address(T2, Isolate::vm_tag_offset()));
 
   // Save the top exit frame info. Use T0 as a temporary register.
   // StackFrameIterator reads the top exit frame info saved in this frame.
   __ lw(T0, Address(T2, Isolate::top_exit_frame_info_offset()));
   __ sw(ZR, Address(T2, Isolate::top_exit_frame_info_offset()));
 
-  // Save the old Context pointer. Use T1 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.
-  __ lw(T1, Address(T2, Isolate::top_context_offset()));
-
-  // The constants kSavedContextSlotFromEntryFp and
   // kExitLinkSlotFromEntryFp must be kept in sync with the code below.
-  ASSERT(kExitLinkSlotFromEntryFp == -23);
-  ASSERT(kSavedContextSlotFromEntryFp == -24);
-  __ sw(T0, Address(SP, 1 * kWordSize));
-  __ sw(T1, Address(SP, 0 * kWordSize));
+  ASSERT(kExitLinkSlotFromEntryFp == -22);
+  __ sw(T0, Address(SP, 0 * kWordSize));
 
   // After the call, The stack pointer is restored to this location.
-  // Pushed A3, S0-7, F20-31, T0, T1 = 23.
+  // Pushed S0-7, F20-31, T0, T1 = 22.
 
   // Load arguments descriptor array into S4, which is passed to Dart code.
   __ lw(S4, Address(A1, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load number of arguments into S5.
   __ lw(T1, FieldAddress(S4, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(T1);
 
   // Compute address of 'arguments array' data area into A2.
   __ lw(A2, Address(A2, VMHandles::kOffsetOfRawPtrInHandle));
@@ skipping 14 matching lines @@
 
   __ Bind(&done_push_arguments);
 
   // Call the Dart code entrypoint.
   // We are calling into Dart code, here, so there is no need to call through
   // T9 to match the ABI.
   __ jalr(A0);  // S4 is the arguments descriptor array.
   __ TraceSimMsg("InvokeDartCodeStub return");
 
   // 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(S6);
 
   // Restore the current VMTag from the stack.
-  __ lw(T1, Address(SP, 2 * kWordSize));
-  __ sw(T1, Address(CTX, Isolate::vm_tag_offset()));
+  __ lw(T1, Address(SP, 1 * kWordSize));
+  __ sw(T1, Address(S6, Isolate::vm_tag_offset()));
 
-  // Restore the saved Context pointer into the Isolate structure.
-  // Uses T1 as a temporary register for this.
   // Restore the saved top exit frame info back into the Isolate structure.
   // Uses T0 as a temporary register for this.
-  __ lw(T1, Address(SP, 0 * kWordSize));
-  __ lw(T0, Address(SP, 1 * kWordSize));
-  __ sw(T1, Address(CTX, Isolate::top_context_offset()));
-  __ sw(T0, Address(CTX, Isolate::top_exit_frame_info_offset()));
+  __ lw(T0, Address(SP, 0 * kWordSize));
+  __ sw(T0, Address(S6, Isolate::top_exit_frame_info_offset()));
 
   // Restore C++ ABI callee-saved registers.
   for (int i = S0; i <= S7; i++) {
     Register r = static_cast<Register>(i);
-    const intptr_t slot = i - S0 + kPreservedContextSlots;
+    const intptr_t slot = i - S0 + kPreservedSlots;
     __ lw(r, Address(SP, slot * kWordSize));
   }
 
   for (intptr_t i = kAbiFirstPreservedFpuReg;
        i <= kAbiLastPreservedFpuReg; i++) {
     FRegister r = static_cast<FRegister>(i);
     const intptr_t slot =
-        kAbiPreservedCpuRegCount + kPreservedContextSlots + i -
+        kAbiPreservedCpuRegCount + kPreservedSlots + i -
         kAbiFirstPreservedFpuReg;
     __ lwc1(r, Address(SP, slot * kWordSize));
   }
 
-  __ lw(A3, Address(SP, 3 * kWordSize));
   __ addiu(SP, SP, Immediate(kPreservedRegSpace));
 
   // Restore the frame pointer and return.
   __ LeaveFrameAndReturn();
 }
 
 
 // Called for inline allocation of contexts.
 // Input:
 //   T1: number of context variables.
@@ skipping 1231 matching lines @@
   const Register right = T0;
   __ lw(left, Address(SP, 1 * kWordSize));
   __ lw(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp1, temp2);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS