PPC/s390: [heap] New heuristics for incremental marking step size.

Port: 1beb89f2

This patch simplifies code for speeding up marking and
removes write barrier counter.

The step size is now computed based in two parts:
- bytes to mark in order to keep up with allocation,
- bytes to mark in order to make progress.

R=mvstanton@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com, bjaideep@ca.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2378053003
Cr-Commit-Position: refs/heads/master@{#39876}

src/ppc/code-stubs-ppc.cc

@@ -3120,19 +3120,6 @@ void RecordWriteStub::CheckNeedsToInformIncrementalMarker(
   Label need_incremental;
   Label need_incremental_pop_scratch;
 
-  DCHECK((~Page::kPageAlignmentMask & 0xffff) == 0);
-  __ lis(r0, Operand((~Page::kPageAlignmentMask >> 16)));
-  __ and_(regs_.scratch0(), regs_.object(), r0);
-  __ LoadP(
-      regs_.scratch1(),
-      MemOperand(regs_.scratch0(), MemoryChunk::kWriteBarrierCounterOffset));
-  __ subi(regs_.scratch1(), regs_.scratch1(), Operand(1));
-  __ StoreP(
-      regs_.scratch1(),
-      MemOperand(regs_.scratch0(), MemoryChunk::kWriteBarrierCounterOffset));
-  __ cmpi(regs_.scratch1(), Operand::Zero());  // PPC, we could do better here
-  __ blt(&need_incremental);
-
   // Let's look at the color of the object:  If it is not black we don't have
   // to inform the incremental marker.
   __ JumpIfBlack(regs_.object(), regs_.scratch0(), regs_.scratch1(), &on_black);

src/s390/code-stubs-s390.cc

@@ -3064,18 +3064,6 @@ void RecordWriteStub::CheckNeedsToInformIncrementalMarker(
   Label need_incremental;
   Label need_incremental_pop_scratch;
 
-  DCHECK((~Page::kPageAlignmentMask & 0xffff) == 0);
-  __ AndP(regs_.scratch0(), regs_.object(), Operand(~Page::kPageAlignmentMask));
-  __ LoadP(
-      regs_.scratch1(),
-      MemOperand(regs_.scratch0(), MemoryChunk::kWriteBarrierCounterOffset));
-  __ SubP(regs_.scratch1(), regs_.scratch1(), Operand(1));
-  __ StoreP(
-      regs_.scratch1(),
-      MemOperand(regs_.scratch0(), MemoryChunk::kWriteBarrierCounterOffset));
-  __ CmpP(regs_.scratch1(), Operand::Zero());  // S390, we could do better here
-  __ blt(&need_incremental);
-
   // Let's look at the color of the object:  If it is not black we don't have
   // to inform the incremental marker.
   __ JumpIfBlack(regs_.object(), regs_.scratch0(), regs_.scratch1(), &on_black);