Call a stub for the write barrier on ARM. This is a step

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
===================================================================
--- src/arm/macro-assembler-arm.cc	(revision 8184)
+++ src/arm/macro-assembler-arm.cc	(working copy)
@@ -482,6 +482,7 @@
     int offset,
     Register value,
     Register dst,
+    LinkRegisterStatus lr_status,
     SaveFPRegsMode save_fp,
     RememberedSetAction remembered_set_action,
     SmiCheck smi_check) {
@@ -506,8 +507,13 @@
     bind(&ok);
   }
 
-  RecordWrite(
-      object, dst, value, save_fp, remembered_set_action, OMIT_SMI_CHECK);
+  RecordWrite(object,
+              dst,
+              value,
+              lr_status,
+              save_fp,
+              remembered_set_action,
+              OMIT_SMI_CHECK);
 
   bind(&done);
 
@@ -525,38 +531,60 @@
 // tag is shifted away.
 void MacroAssembler::RecordWrite(Register object,
                                  Register address,
-                                 Register scratch,
+                                 Register value,
+                                 LinkRegisterStatus lr_status,
                                  SaveFPRegsMode fp_mode,
                                  RememberedSetAction remembered_set_action,
                                  SmiCheck smi_check) {
   // The compiled code assumes that record write doesn't change the
   // context register, so we check that none of the clobbered
   // registers are cp.
-  ASSERT(!address.is(cp) && !scratch.is(cp));
+  ASSERT(!address.is(cp) && !value.is(cp));
 
   Label done;
 
-  // First, test that the object is not in the new space.  We cannot set
-  // region marks for new space pages.
-  InNewSpace(object, scratch, eq, &done);
+  if (smi_check == INLINE_SMI_CHECK) {
+    ASSERT_EQ(0, kSmiTag);
+    tst(value, Operand(kSmiTagMask));
+    b(eq, &done);
+  }
 
+  CheckPageFlag(value,
+                value,  // Used as scratch.
+                MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING,
+                eq,
+                &done);
+  CheckPageFlag(object,
+                value,  // Used as scratch.
+                MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING,
+                eq,
+                &done);
+
   // Record the actual write.
-  RememberedSetHelper(address, scratch, fp_mode);
+  if (lr_status == kLRHasNotBeenSaved) {
+    push(lr);
+  }
+  RecordWriteStub stub(object, value, address, remembered_set_action, fp_mode);
+  CallStub(&stub);
+  if (lr_status == kLRHasNotBeenSaved) {
+    pop(lr);
+  }
 
   bind(&done);
 
-  // Clobber all input registers when running with the debug-code flag
+  // Clobber clobbered registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     mov(address, Operand(BitCast<int32_t>(kZapValue + 12)));
-    mov(scratch, Operand(BitCast<int32_t>(kZapValue + 16)));
+    mov(value, Operand(BitCast<int32_t>(kZapValue + 16)));
   }
 }
 
 
 void MacroAssembler::RememberedSetHelper(Register address,
                                          Register scratch,
-                                         SaveFPRegsMode fp_mode) {
+                                         SaveFPRegsMode fp_mode,
+                                         RememberedSetFinalAction and_then) {
   Label done;
   // Load store buffer top.
   ExternalReference store_buffer =
@@ -570,13 +598,21 @@
   // Call stub on end of buffer.
   // Check for end of buffer.
   tst(scratch, Operand(StoreBuffer::kStoreBufferOverflowBit));
-  b(eq, &done);
+  if (and_then == kFallThroughAtEnd) {
+    b(eq, &done);
+  } else {
+    ASSERT(and_then == kReturnAtEnd);
+    Ret(ne);
+  }
   push(lr);
   StoreBufferOverflowStub store_buffer_overflow =
       StoreBufferOverflowStub(fp_mode);
   CallStub(&store_buffer_overflow);
   pop(lr);
   bind(&done);
+  if (and_then == kReturnAtEnd) {
+    Ret();
+  }
 }
 
 
@@ -3092,6 +3128,60 @@
 }
 
 
+void MacroAssembler::IsBlack(Register object,
+                             Register scratch0,
+                             Register scratch1,
+                             Label* is_black) {
+  HasColour(object, scratch0, scratch1,
+            is_black,
+            1, 0);  // kBlackBitPattern.
+  ASSERT(strcmp(Marking::kBlackBitPattern, "10") == 0);
+}
+
+
+void MacroAssembler::HasColour(Register object,

[Lasse Reichstein, 2011/06/07 08:48:37]

I think we generally use the Bowdlerized US English spelling, however much it
might hurt.
Variables too.

[Erik Corry, 2011/06/08 10:31:29]

Auch!  That hert!

+                               Register bitmap_scratch,
+                               Register mask_scratch,
+                               Label* has_colour,
+                               int first_bit,
+                               int second_bit) {
+  ASSERT(!Aliasing(object, bitmap_scratch, mask_scratch, no_reg));
+
+  MarkBits(object, bitmap_scratch, mask_scratch);

[Lasse Reichstein, 2011/06/07 08:48:37]

Could MarkBits be named something that sounds less imperative? I get confused as
to whether it actually marks any bits, or just finds the address/mask of the
mark-bits.
Something like GetMarkBitAddressAndMask would perhaps be too long, but more
readable.

[Erik Corry, 2011/06/08 10:31:29]

GetMarkBits

+
+  Label other_colour, word_boundary;
+  ldr(ip, MemOperand(bitmap_scratch, MemoryChunk::kHeaderSize));
+  tst(ip, Operand(mask_scratch));
+  b(first_bit == 1 ? eq : ne, &other_colour);
+  // Shift left 1 by adding.
+  add(mask_scratch, mask_scratch, Operand(mask_scratch), SetCC);
+  b(eq, &word_boundary);

[Lasse Reichstein, 2011/06/07 08:48:37]

Should this be optimized for speed or size?
If speed, you could probably detect the case where the color overlaps a word
boundary earlier (mask is negative) and have a faster case that tests both bits
in one test if it doesn't.

[Erik Corry, 2011/06/08 10:31:29]

I think there's room for experimentation here, but I'm going to leave that for
later.

+  tst(ip, Operand(mask_scratch));
+  b(second_bit == 1 ? ne : eq, has_colour);
+  jmp(&other_colour);
+
+  bind(&word_boundary);
+  ldr(ip, MemOperand(bitmap_scratch, MemoryChunk::kHeaderSize + kPointerSize));
+  tst(ip, Operand(1));
+  b(second_bit == 1 ? ne : eq, has_colour);
+  bind(&other_colour);
+}
+
+
+void MacroAssembler::MarkBits(Register addr_reg,
+                              Register bitmap_reg,
+                              Register mask_reg) {
+  ASSERT(!Aliasing(addr_reg, bitmap_reg, mask_reg, no_reg));
+  and_(bitmap_reg, addr_reg, Operand(~Page::kPageAlignmentMask));
+  Ubfx(mask_reg, addr_reg, kPointerSizeLog2, Bitmap::kBitsPerCellLog2);
+  const int kLowBits = kPointerSizeLog2 + Bitmap::kBitsPerCellLog2;
+  Ubfx(ip, addr_reg, kLowBits, kPageSizeBits - kLowBits);
+  add(bitmap_reg, bitmap_reg, Operand(ip, LSL, kPointerSizeLog2));
+  mov(ip, Operand(1));
+  mov(mask_reg, Operand(ip, LSL, mask_reg));
+}
+
+
 void MacroAssembler::ClampUint8(Register output_reg, Register input_reg) {
   Usat(output_reg, 8, Operand(input_reg));
 }
@@ -3141,6 +3231,17 @@
 }
 
 
+bool Aliasing(Register r1, Register r2, Register r3, Register r4) {
+  if (r1.is(r2)) return true;
+  if (r1.is(r3)) return true;
+  if (r1.is(r4)) return true;
+  if (r2.is(r3)) return true;
+  if (r2.is(r4)) return true;
+  if (r3.is(r4)) return true;
+  return false;
+}
+
+
 CodePatcher::CodePatcher(byte* address, int instructions)
     : address_(address),
       instructions_(instructions),