X87: Reshuffle registers in JSConstructStub to avoid trashing costructor and new.target on fast pat…

src/x87/builtins-x87.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X87
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 240 matching lines @@
           __ movzx_b(esi, FieldOperand(eax, Map::kUnusedPropertyFieldsOffset));
           __ neg(esi);
           __ lea(esi, Operand(edi, esi, times_pointer_size, 0));
           // esi: offset of first field after pre-allocated fields
           if (FLAG_debug_code) {
             __ cmp(ecx, esi);
             __ Assert(less_equal,
                       kUnexpectedNumberOfPreAllocatedPropertyFields);
           }
           __ InitializeFieldsWithFiller(ecx, esi, edx);
+
+          // To allow truncation fill the remaining fields with one pointer
+          // filler map.
           __ mov(edx, factory->one_pointer_filler_map());
-          // Fill the remaining fields with one pointer filler map.
 
           __ bind(&no_inobject_slack_tracking);
         }
 
         __ InitializeFieldsWithFiller(ecx, edi, edx);
 
         // Add the object tag to make the JSObject real, so that we can continue
         // and jump into the continuation code at any time from now on.
         // ebx: JSObject (untagged)
         __ or_(ebx, Immediate(kHeapObjectTag));
@@ skipping 1713 matching lines @@
 
   __ bind(&ok);
   __ ret(0);
 }
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X87