Changeset 175593 in webkit for trunk/Source/JavaScriptCore/llint

Timestamp:

Nov 4, 2014, 5:19:37 PM (11 years ago)

Author:

[email protected]

Message:

Rename checkMarkByte() to jumpIfIsRememberedOrInEden().
<​https://webkit.org/b/138369>

Reviewed by Geoffrey Garen.

Write barriers are needed for GC Eden collections so that we can scan pointers
pointing from old generation objects to eden generation objects. The barrier
currently checks the mark byte in a cell to see if we should skip adding the
cell to the GC remembered set. The addition should be skipped if:

1. The cell is in the young generation. It has no old to eden pointers by definition.
2. The cell is already in the remembered set. While it is ok to add the cell to the GC remembered set more than once, it would be redundant. Hence, we skip this as an optimization to avoid doing unnecessary work.

The barrier currently names this check as checkMarkByte(). We should rename it
to jumpIfIsRememberedOrInEden() to be clearer about its intent.

Similarly, Jump results of this check are currently named
ownerNotMarkedOrAlreadyRemembered. This can be misinterpreted as the owner is
not marked or not already remembered. We should rename it to
ownerIsRememberedOrInEden which is clearer about the intent of the
check. What we are really checking for is that the cell is in the eden gen,
which is implied by it being "not marked".

• dfg/DFGOSRExitCompilerCommon.cpp:

(JSC::DFG::osrWriteBarrier):

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::writeBarrier):

• dfg/DFGSpeculativeJIT32_64.cpp:

(JSC::DFG::SpeculativeJIT::writeBarrier):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::writeBarrier):

• jit/AssemblyHelpers.h:

(JSC::AssemblyHelpers::jumpIfIsRememberedOrInEden):
(JSC::AssemblyHelpers::checkMarkByte): Deleted.

• jit/JITPropertyAccess.cpp:

(JSC::JIT::emitWriteBarrier):

• llint/LowLevelInterpreter.asm:
• llint/LowLevelInterpreter32_64.asm:
• llint/LowLevelInterpreter64.asm:
• runtime/JSCell.h:

Location:

trunk/Source/JavaScriptCore/llint

Files:

• LowLevelInterpreter.asm (modified) (1 diff)
• LowLevelInterpreter32_64.asm (modified) (2 diffs)
• LowLevelInterpreter64.asm (modified) (2 diffs)

trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.asm

@@ -510 +510 @@
 end
 
-macro checkMarkByte(cell, scratch1, scratch2, continuation)
+macro skipIfIsRememberedOrInEden(cell, scratch1, scratch2, continuation)
     loadb JSCell::m_gcData[cell], scratch1
     continuation(scratch1)

trunk/Source/JavaScriptCore/llint/LowLevelInterpreter32_64.asm

@@ -570 +570 @@
         loadisFromInstruction(cellOperand, t1)
         loadConstantOrVariablePayload(t1, CellTag, t2, .writeBarrierDone)
-        checkMarkByte(t2, t1, t3, 
+        skipIfIsRememberedOrInEden(t2, t1, t3, 
             macro(gcData)
                 btbnz gcData, .writeBarrierDone
@@ -604 +604 @@
         loadp CodeBlock[cfr], t3
         loadp CodeBlock::m_globalObject[t3], t3
-        checkMarkByte(t3, t1, t2,
+        skipIfIsRememberedOrInEden(t3, t1, t2,
             macro(gcData)
                 btbnz gcData, .writeBarrierDone

trunk/Source/JavaScriptCore/llint/LowLevelInterpreter64.asm

@@ -444 +444 @@
         loadisFromInstruction(cellOperand, t1)
         loadConstantOrVariableCell(t1, t2, .writeBarrierDone)
-        checkMarkByte(t2, t1, t3, 
+        skipIfIsRememberedOrInEden(t2, t1, t3, 
             macro(gcData)
                 btbnz gcData, .writeBarrierDone
@@ -475 +475 @@
         loadp CodeBlock[cfr], t3
         loadp CodeBlock::m_globalObject[t3], t3
-        checkMarkByte(t3, t1, t2,
+        skipIfIsRememberedOrInEden(t3, t1, t2,
             macro(gcData)
                 btbnz gcData, .writeBarrierDone