https://codereview.chromium.org/893073006/diff/1/src/ia32/lithium-codegen-ia32.cc
File src/ia32/lithium-codegen-ia32.cc (right):
https://codereview.chromium.org/893073006/diff/1/src/ia32/lithium-codegen-ia32.cc#newcode2995
src/ia32/lithium-codegen-ia32.cc:2995: __ mov(result,
FieldOperand(object, HeapObject::kMapOffset));
On 2015/02/04 10:49:42, Erik Corry wrote:
On 2015/02/04 09:35:04, ulan wrote:
> __ mov(FieldOperand(object, HeapObject::kMapOffset), result);
This is intended to be a store, not a load.
Yep. The destination of the mov is the first argument :)
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/ia32/assembler-ia32.h&l=638
https://codereview.chromium.org/893073006/diff/1/src/ic/ia32/ic-compiler-ia32.cc
File src/ic/ia32/ic-compiler-ia32.cc (right):
https://codereview.chromium.org/893073006/diff/1/src/ic/ia32/ic-compiler-ia32.cc#newcode117
src/ic/ia32/ic-compiler-ia32.cc:117: Handle<WeakCell> cell =
Map::WeakCellForMap(transitioned_maps->at(i));
On 2015/02/04 10:49:42, Erik Corry wrote:
On 2015/02/04 09:35:04, ulan wrote:
> On 2015/02/03 17:42:53, Erik Corry http://Chromium.org wrote:
> > I think perhaps here we should trigger the read barrier on the
first cell
> (yeah
> > there are two variables called cell in this function!) to show
that it is in
> use
> > and should not be cleared on GC. What do you think?
>
> Do you mean read barrier on receiver_map? I think we don't need it.
If the
> compare succeeds than we already have the receiver map in register,
so it must
> be alive. If the compare fails, then we have no information and we
didn't
"use"
> the map.
I agree we don't need it for correctness. The question is whether it
could be
useful for tracking whether the map was recently used, so that we can
extend its
life in GC even if there are no live objects using it at the next GC.
But I'm
not exactly sure what's going on here: Does this count as a recent use
that
should prevent weak map clearing at the next GC?
The transitioned_map[i] has a back pointer to the current map (which is
equal to the receiver_map[i] since the map check succeeded). So I think
the read barrier for transitioned_map[i] would keep also receiver_map[i]
alive.
https://codereview.chromium.org/893073006/
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