ARM: Add literal pool blocking to position critical code.

src/arm/code-stubs-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 3719 matching lines @@
 
   __ mov(r2, Operand(ExternalReference::isolate_address()));
 
   // To let the GC traverse the return address of the exit frames, we need to
   // know where the return address is. The CEntryStub is unmovable, so
   // we can store the address on the stack to be able to find it again and
   // we never have to restore it, because it will not change.
   // Compute the return address in lr to return to after the jump below. Pc is
   // already at '+ 8' from the current instruction but return is after three
   // instructions so add another 4 to pc to get the return address.
-  masm->add(lr, pc, Operand(4));
-  __ str(lr, MemOperand(sp, 0));
-  masm->Jump(r5);
+  {
+    // Prevent literal pool emission before return address.
+    Assembler::BlockConstPoolScope block_const_pool(masm);
+    masm->add(lr, pc, Operand(4));
+    __ str(lr, MemOperand(sp, 0));
+    masm->Jump(r5);
+  }
 
   if (always_allocate) {
     // It's okay to clobber r2 and r3 here. Don't mess with r0 and r1
     // though (contain the result).
     __ mov(r2, Operand(scope_depth));
     __ ldr(r3, MemOperand(r2));
     __ sub(r3, r3, Operand(1));
     __ str(r3, MemOperand(r2));
   }
 
@@ skipping 196 matching lines @@
   Label cont;
   __ b(&cont);
   __ bind(&non_outermost_js);
   __ mov(ip, Operand(Smi::FromInt(StackFrame::INNER_JSENTRY_FRAME)));
   __ bind(&cont);
   __ push(ip);
 
   // Jump to a faked try block that does the invoke, with a faked catch
   // block that sets the pending exception.
   __ jmp(&invoke);
-  __ bind(&handler_entry);
-  handler_offset_ = handler_entry.pos();
-  // Caught exception: Store result (exception) in the pending exception
-  // field in the JSEnv and return a failure sentinel.  Coming in here the
-  // fp will be invalid because the PushTryHandler below sets it to 0 to
-  // signal the existence of the JSEntry frame.
-  __ mov(ip, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
-                                       isolate)));
+
+  // Block literal pool emission whilst taking the position of the handler
+  // entry. This avoids making the assumption that literal pools are always
+  // emitted after an instruction is emitted, rather than before.
+  {
+    Assembler::BlockConstPoolScope block_const_pool(masm);
+    __ bind(&handler_entry);
+    handler_offset_ = handler_entry.pos();
+    // Caught exception: Store result (exception) in the pending exception
+    // field in the JSEnv and return a failure sentinel.  Coming in here the
+    // fp will be invalid because the PushTryHandler below sets it to 0 to
+    // signal the existence of the JSEntry frame.
+    __ mov(ip, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+                                         isolate)));
+  }
   __ str(r0, MemOperand(ip));
   __ mov(r0, Operand(reinterpret_cast<int32_t>(Failure::Exception())));
   __ b(&exit);
 
   // Invoke: Link this frame into the handler chain.  There's only one
   // handler block in this code object, so its index is 0.
   __ bind(&invoke);
   // Must preserve r0-r4, r5-r7 are available.
   __ PushTryHandler(StackHandler::JS_ENTRY, 0);
   // If an exception not caught by another handler occurs, this handler
@@ skipping 22 matching lines @@
                                       isolate);
     __ mov(ip, Operand(construct_entry));
   } else {
     ExternalReference entry(Builtins::kJSEntryTrampoline, isolate);
     __ mov(ip, Operand(entry));
   }
   __ ldr(ip, MemOperand(ip));  // deref address
 
   // Branch and link to JSEntryTrampoline.  We don't use the double underscore
   // macro for the add instruction because we don't want the coverage tool
-  // inserting instructions here after we read the pc.
-  __ mov(lr, Operand(pc));
-  masm->add(pc, ip, Operand(Code::kHeaderSize - kHeapObjectTag));
+  // inserting instructions here after we read the pc. We block literal pool
+  // emission for the same reason.
+  {
+    Assembler::BlockConstPoolScope block_const_pool(masm);
+    __ mov(lr, Operand(pc));
+    masm->add(pc, ip, Operand(Code::kHeaderSize - kHeapObjectTag));
+  }
 
   // Unlink this frame from the handler chain.
   __ PopTryHandler();
 
   __ bind(&exit);  // r0 holds result
   // Check if the current stack frame is marked as the outermost JS frame.
   Label non_outermost_js_2;
   __ pop(r5);
   __ cmp(r5, Operand(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
   __ b(ne, &non_outermost_js_2);
@@ skipping 2783 matching lines @@
                                     ExternalReference function) {
   __ mov(r2, Operand(function));
   GenerateCall(masm, r2);
 }
 
 
 void DirectCEntryStub::GenerateCall(MacroAssembler* masm,
                                     Register target) {
   __ mov(lr, Operand(reinterpret_cast<intptr_t>(GetCode().location()),
                      RelocInfo::CODE_TARGET));
+
+  // Prevent literal pool emission during calculation of return address.
+  Assembler::BlockConstPoolScope block_const_pool(masm);
+
   // Push return address (accessible to GC through exit frame pc).
   // Note that using pc with str is deprecated.
   Label start;
   __ bind(&start);
   __ add(ip, pc, Operand(Assembler::kInstrSize));
   __ str(ip, MemOperand(sp, 0));
   __ Jump(target);  // Call the C++ function.
   ASSERT_EQ(Assembler::kInstrSize + Assembler::kPcLoadDelta,
             masm->SizeOfCodeGeneratedSince(&start));
 }
@@ skipping 340 matching lines @@
 // written is in the address register.
 void RecordWriteStub::Generate(MacroAssembler* masm) {
   Label skip_to_incremental_noncompacting;
   Label skip_to_incremental_compacting;
 
   // The first two instructions are generated with labels so as to get the
   // offset fixed up correctly by the bind(Label*) call.  We patch it back and
   // forth between a compare instructions (a nop in this position) and the
   // real branch when we start and stop incremental heap marking.
   // See RecordWriteStub::Patch for details.
-  __ b(&skip_to_incremental_noncompacting);
-  __ b(&skip_to_incremental_compacting);
+  {
+    // Block literal pool emission, as the position of these two instructions
+    // is assumed by the patching code.
+    Assembler::BlockConstPoolScope block_const_pool(masm);
+    __ b(&skip_to_incremental_noncompacting);
+    __ b(&skip_to_incremental_compacting);
+  }
 
   if (remembered_set_action_ == EMIT_REMEMBERED_SET) {
     __ RememberedSetHelper(object_,
                            address_,
                            value_,
                            save_fp_regs_mode_,
                            MacroAssembler::kReturnAtEnd);
   }
   __ Ret();
 
@@ skipping 218 matching lines @@
   __ StoreNumberToDoubleElements(r0, r3, r1, r5, r6, r7, r9, r2,
                                  &slow_elements);
   __ Ret();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM