Improve page flag checking sequence on ARM.

src/arm/macro-assembler-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 345 matching lines @@
     bic(dst, dst, Operand(mask));
     and_(scratch, src, Operand((1 << width) - 1));
     mov(scratch, Operand(scratch, LSL, lsb));
     orr(dst, dst, scratch);
   } else {
     bfi(dst, src, lsb, width, cond);
   }
 }
 
 
-void MacroAssembler::Bfc(Register dst, int lsb, int width, Condition cond) {
+void MacroAssembler::Bfc(Register dst, Register src, int lsb, int width,
+                         Condition cond) {
   ASSERT(lsb < 32);
   if (!CpuFeatures::IsSupported(ARMv7) || predictable_code_size()) {
     int mask = (1 << (width + lsb)) - 1 - ((1 << lsb) - 1);
-    bic(dst, dst, Operand(mask));
+    bic(dst, src, Operand(mask));
   } else {
+    Move(dst, src, cond);
     bfc(dst, lsb, width, cond);
   }
 }
 
 
 void MacroAssembler::Usat(Register dst, int satpos, const Operand& src,
                           Condition cond) {
   if (!CpuFeatures::IsSupported(ARMv7) || predictable_code_size()) {
     ASSERT(!dst.is(pc) && !src.rm().is(pc));
     ASSERT((satpos >= 0) && (satpos <= 31));
@@ skipping 3108 matching lines @@
   add(result, result, Operand(kPCRegOffset));
 }
 
 
 void MacroAssembler::CheckPageFlag(
     Register object,
     Register scratch,
     int mask,
     Condition cc,
     Label* condition_met) {
-  and_(scratch, object, Operand(~Page::kPageAlignmentMask));
+  Bfc(scratch, object, 0, kPageSizeBits);
   ldr(scratch, MemOperand(scratch, MemoryChunk::kFlagsOffset));
   tst(scratch, Operand(mask));
   b(cc, condition_met);
 }
 
 
 void MacroAssembler::JumpIfBlack(Register object,
                                  Register scratch0,
                                  Register scratch1,
                                  Label* on_black) {
@@ skipping 343 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM