Make CTX allocatable by the register allocator.

runtime/vm/stub_code_ia32.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_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 29 matching lines @@
 //   EDX : number of arguments to the call.
 // Must preserve callee saved registers EDI and EBX.
 void StubCode::GenerateCallToRuntimeStub(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();
 
   __ EnterFrame(0);
 
   __ LoadIsolate(EAX);

[Vyacheslav Egorov (Google), 2014/10/28 13:44:58]

if you were to load isolate into EAX into a callee-save register then there
would be no need to reload it after the native call below

[Florian Schneider, 2014/10/28 19:04:31]

Done.

 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
   __ movl(Address(EAX, Isolate::top_exit_frame_info_offset()), ESP);
 
 #if defined(DEBUG)
-  if (FLAG_verify_incoming_contexts) {
-    Label ok;
-    // Check that the isolate's saved ctx is null.
-    const Immediate& raw_null =
-        Immediate(reinterpret_cast<intptr_t>(Object::null()));
-    __ cmpl(Address(EAX, Isolate::top_context_offset()), raw_null);
-    __ j(EQUAL, &ok, Assembler::kNearJump);
-    __ Stop("Found non-null incoming top context: call to runtime stub");
-    __ Bind(&ok);
-  }
-#endif
-
-  // Save current Context pointer into Isolate structure.
-  __ movl(Address(EAX, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing runtime code.
-  __ movl(CTX, EAX);
-
-#if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ movl(EAX, Address(CTX, Isolate::vm_tag_offset()));
-    __ cmpl(EAX, Immediate(VMTag::kDartTagId));
+    __ cmpl(Address(EAX, Isolate::vm_tag_offset()),
+            Immediate(VMTag::kDartTagId));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing VM code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()), ECX);
+  __ movl(Address(EAX, Isolate::vm_tag_offset()), ECX);
 
   // Reserve space for arguments and align frame before entering C++ world.
   __ AddImmediate(ESP, Immediate(-INT32_SIZEOF(NativeArguments)));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andl(ESP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call runtime.
-  __ movl(Address(ESP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movl(Address(ESP, isolate_offset), EAX);  // 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_.
   __ movl(Address(ESP, argc_tag_offset), EDX);  // Set argc in NativeArguments.
   __ leal(EAX, Address(EBP, EDX, TIMES_4, 1 * kWordSize));  // Compute argv.
   __ movl(Address(ESP, argv_offset), EAX);  // Set argv in NativeArguments.
   __ addl(EAX, Immediate(1 * kWordSize));  // Retval is next to 1st argument.
   __ movl(Address(ESP, retval_offset), EAX);  // Set retval in NativeArguments.
   __ call(ECX);
 
   // Mark that the isolate is executing Dart code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+  __ LoadIsolate(EAX);
+  __ movl(Address(EAX, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into ECX.
-  __ movl(ECX, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ movl(Address(CTX, Isolate::top_context_offset()), raw_null);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movl(CTX, ECX);
+  __ movl(Address(EAX, 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 34 matching lines @@
 
   __ EnterFrame(0);
 
   __ LoadIsolate(EDI);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to dart VM code.
   __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), ESP);
 
 #if defined(DEBUG)
-  if (FLAG_verify_incoming_contexts) {
-    Label ok;
-    // Check that the isolate's saved ctx is null.
-    const Immediate& raw_null =
-        Immediate(reinterpret_cast<intptr_t>(Object::null()));
-    __ cmpl(Address(EDI, Isolate::top_context_offset()), raw_null);
-    __ j(EQUAL, &ok, Assembler::kNearJump);
-    __ Stop("Found non-null incoming top context: "
-            "call to native c function stub");
-    __ Bind(&ok);
-  }
-#endif
-
-  // Save current Context pointer into Isolate structure.
-  __ movl(Address(EDI, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ movl(CTX, EDI);
-
-#if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ movl(EDI, Address(CTX, Isolate::vm_tag_offset()));
-    __ cmpl(EDI, Immediate(VMTag::kDartTagId));
+    __ cmpl(Address(EDI, Isolate::vm_tag_offset()),
+            Immediate(VMTag::kDartTagId));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()), ECX);
+  __ movl(Address(EDI, Isolate::vm_tag_offset()), ECX);
 
   // Reserve space for the native arguments structure, the outgoing parameters
   // (pointer to the native arguments structure, the C function entry point)
   // and align frame before entering the C++ world.
   __ AddImmediate(ESP,
                   Immediate(-INT32_SIZEOF(NativeArguments) - (2 * kWordSize)));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andl(ESP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call native function.
-  __ movl(Address(ESP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movl(Address(ESP, isolate_offset), EDI);  // Set isolate in NativeArgs.
   __ movl(Address(ESP, argc_tag_offset), EDX);  // Set argc in NativeArguments.
   __ movl(Address(ESP, argv_offset), EAX);  // Set argv in NativeArguments.
   __ leal(EAX, Address(EBP, 2 * kWordSize));  // Compute return value addr.
   __ movl(Address(ESP, retval_offset), EAX);  // Set retval in NativeArguments.
   __ leal(EAX, Address(ESP, 2 * kWordSize));  // Pointer to the NativeArguments.
   __ movl(Address(ESP, 0), EAX);  // Pass the pointer to the NativeArguments.
 
   __ movl(Address(ESP, kWordSize), ECX);  // Function to call.
   __ call(&NativeEntry::NativeCallWrapperLabel());
 
   // Mark that the isolate is executing Dart code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+  __ LoadIsolate(EDI);
+  __ movl(Address(EDI, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into EDI.
-  __ movl(EDI, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ movl(Address(CTX, Isolate::top_context_offset()), raw_null);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movl(CTX, EDI);
+  __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
   __ LeaveFrame();
   __ ret();
 }
 
 
 // Input parameters:
 //   ESP : points to return address.
 //   ESP + 4 : address of return value.
 //   EAX : address of first argument in argument array.
@@ skipping 13 matching lines @@
 
   __ EnterFrame(0);
 
   __ LoadIsolate(EDI);
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to dart VM code.
   __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), ESP);
 
 #if defined(DEBUG)
-  if (FLAG_verify_incoming_contexts) {
-    Label ok;
-    // Check that the isolate's saved ctx is null.
-    const Immediate& raw_null =
-        Immediate(reinterpret_cast<intptr_t>(Object::null()));
-    __ cmpl(Address(EDI, Isolate::top_context_offset()), raw_null);
-    __ j(EQUAL, &ok, Assembler::kNearJump);
-    __ Stop("Found non-null incoming top context: "
-            "call to bootstrap c function stub");
-    __ Bind(&ok);
-  }
-#endif
-
-  // Save current Context pointer into Isolate structure.
-  __ movl(Address(EDI, Isolate::top_context_offset()), CTX);
-
-  // Cache Isolate pointer into CTX while executing native code.
-  __ movl(CTX, EDI);
-
-#if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
-    __ movl(EDI, Address(CTX, Isolate::vm_tag_offset()));
-    __ cmpl(EDI, Immediate(VMTag::kDartTagId));
+    __ cmpl(Address(EDI, Isolate::vm_tag_offset()),
+            Immediate(VMTag::kDartTagId));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Not coming from Dart code.");
     __ Bind(&ok);
   }
 #endif
 
   // Mark that the isolate is executing Native code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()), ECX);
+  __ movl(Address(EDI, Isolate::vm_tag_offset()), ECX);
 
   // Reserve space for the native arguments structure, the outgoing parameter
   // (pointer to the native arguments structure) and align frame before
   // entering the C++ world.
   __ AddImmediate(ESP, Immediate(-INT32_SIZEOF(NativeArguments) - kWordSize));
   if (OS::ActivationFrameAlignment() > 1) {
     __ andl(ESP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 
   // Pass NativeArguments structure by value and call native function.
-  __ movl(Address(ESP, isolate_offset), CTX);  // Set isolate in NativeArgs.
+  __ movl(Address(ESP, isolate_offset), EDI);  // Set isolate in NativeArgs.
   __ movl(Address(ESP, argc_tag_offset), EDX);  // Set argc in NativeArguments.
   __ movl(Address(ESP, argv_offset), EAX);  // Set argv in NativeArguments.
   __ leal(EAX, Address(EBP, 2 * kWordSize));  // Compute return value addr.
   __ movl(Address(ESP, retval_offset), EAX);  // Set retval in NativeArguments.
   __ leal(EAX, Address(ESP, kWordSize));  // Pointer to the NativeArguments.
   __ movl(Address(ESP, 0), EAX);  // Pass the pointer to the NativeArguments.
   __ call(ECX);
 
   // Mark that the isolate is executing Dart code.
-  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+  __ LoadIsolate(EDI);

[Vyacheslav Egorov (Google), 2014/10/28 13:44:58]

no need to reload, EDI and ESI are both callee save.

[Florian Schneider, 2014/10/28 19:04:31]

Done.

+  __ movl(Address(EDI, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Reset exit frame information in Isolate structure.
-  __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
-
-  // Load Context pointer from Isolate structure into EDI.
-  __ movl(EDI, Address(CTX, Isolate::top_context_offset()));
-
-  // Reset Context pointer in Isolate structure.
-  const Immediate& raw_null =
-      Immediate(reinterpret_cast<intptr_t>(Object::null()));
-  __ movl(Address(CTX, Isolate::top_context_offset()), raw_null);
-
-  // Cache Context pointer into CTX while executing Dart code.
-  __ movl(CTX, EDI);
+  __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
   __ LeaveFrame();
   __ ret();
 }
 
 
 // Input parameters:
 //   EDX: arguments descriptor array.
 void StubCode::GenerateCallStaticFunctionStub(Assembler* assembler) {
   const Immediate& raw_null =
@@ skipping 429 matching lines @@
   const intptr_t kNewContextOffset = 5 * kWordSize;
 
   // Save frame pointer coming in.
   __ EnterFrame(0);
 
   // Save C++ ABI callee-saved registers.
   __ pushl(EBX);
   __ pushl(ESI);
   __ pushl(EDI);
 
-  // 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.
+  // Pass the new Context pointer in CTX while executing dart code.
   __ movl(CTX, Address(EBP, kNewContextOffset));
   __ movl(CTX, Address(CTX, VMHandles::kOffsetOfRawPtrInHandle));
 
   __ LoadIsolate(EDI);
 
   // Save the current VMTag on the stack.
   ASSERT(kSavedVMTagSlotFromEntryFp == -4);
   __ movl(ECX, Address(EDI, Isolate::vm_tag_offset()));
   __ pushl(ECX);
 
   // Mark that the isolate is executing Dart code.
   __ movl(Address(EDI, Isolate::vm_tag_offset()),
           Immediate(VMTag::kDartTagId));
 
   // Save the top exit frame info. Use EDX 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.
   ASSERT(kExitLinkSlotFromEntryFp == -5);
   __ movl(EDX, Address(EDI, Isolate::top_exit_frame_info_offset()));
   __ pushl(EDX);
   __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
-  // Save the old Context pointer. Use ECX 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.
-  // The constant kSavedContextSlotFromEntryFp must be kept in sync with
-  // the code below.
-  ASSERT(kSavedContextSlotFromEntryFp == -6);
-  __ movl(ECX, Address(EDI, Isolate::top_context_offset()));
-  __ pushl(ECX);
-
-  // TODO(turnidge): This code should probably be emitted all the time
-  // on all architectures but I am leaving it under DEBUG/flag for
-  // now.
-#if defined(DEBUG)
-  if (FLAG_verify_incoming_contexts) {
-    // Clear Context pointer in Isolate structure.
-    const Immediate& raw_null =
-        Immediate(reinterpret_cast<intptr_t>(Object::null()));
-    __ movl(Address(EDI, Isolate::top_context_offset()), raw_null);
-  }
-#endif
-
   // Load arguments descriptor array into EDX.
   __ movl(EDX, Address(EBP, kArgumentsDescOffset));
   __ movl(EDX, Address(EDX, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load number of arguments into EBX.
   __ movl(EBX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(EBX);
 
   // Set up arguments for the dart call.
   Label push_arguments;
@@ skipping 23 matching lines @@
   __ movl(CTX, Address(CTX, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Reread the arguments descriptor array to obtain the number of passed
   // arguments.
   __ movl(EDX, Address(EBP, kArgumentsDescOffset));
   __ movl(EDX, Address(EDX, VMHandles::kOffsetOfRawPtrInHandle));
   __ movl(EDX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   // Get rid of arguments pushed on the stack.
   __ leal(ESP, Address(ESP, EDX, TIMES_2, 0));  // EDX is a Smi.
 
-  // Load Isolate pointer into CTX. Drop Context.
-  __ LoadIsolate(CTX);
-
-  // Restore the saved Context pointer into the Isolate structure.
-  __ popl(Address(CTX, Isolate::top_context_offset()));
-
   // Restore the saved top exit frame info back into the Isolate structure.
-  __ popl(Address(CTX, Isolate::top_exit_frame_info_offset()));
+  __ LoadIsolate(EDI);
+  __ popl(Address(EDI, Isolate::top_exit_frame_info_offset()));
 
   // Restore the current VMTag from the stack.
-  __ popl(Address(CTX, Isolate::vm_tag_offset()));
+  __ popl(Address(EDI, Isolate::vm_tag_offset()));
 
   // Restore C++ ABI callee-saved registers.
   __ popl(EDI);
   __ popl(ESI);
   __ popl(EBX);
 
   // Restore the frame pointer.
   __ LeaveFrame();
 
   __ ret();
@@ skipping 487 matching lines @@
     __ movl(EBX, FieldAddress(ECX, ICData::state_bits_offset()));
     ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
     __ andl(EBX, Immediate(ICData::NumArgsTestedMask()));
     __ cmpl(EBX, Immediate(num_args));
     __ j(EQUAL, &ok, Assembler::kNearJump);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
-  // Check single stepping.
   Label stepping, done_stepping;
   uword single_step_address = reinterpret_cast<uword>(Isolate::Current()) +
       Isolate::single_step_offset();
   __ cmpb(Address::Absolute(single_step_address), Immediate(0));
   __ j(NOT_EQUAL, &stepping);
   __ Bind(&done_stepping);
 
   if (kind != Token::kILLEGAL) {
     Label not_smi_or_overflow;
     EmitFastSmiOp(assembler, kind, num_args, &not_smi_or_overflow);
@@ skipping 657 matching lines @@
   const Register temp = ECX;
   __ movl(left, Address(ESP, 2 * kWordSize));
   __ movl(right, Address(ESP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32