Write barrier audit: Verify previous value in generated code.

Write barrier audit: Verify previous value in generated code.

Always use far jumps in verified mem mode, rather than clutter the code with tests everywhere.

Committed: https://code.google.com/p/dart/source/detail?r=41785

[Ivan Posva, 2014-11-14 22:09:12]

LGTMwC -ip

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
File runtime/vm/assembler_ia32.cc (right):

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
runtime/vm/assembler_ia32.cc:2208: void Assembler::Verify(const Address& dest) {
Verify is a bit too generic a name for this functionality.

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
runtime/vm/assembler_ia32.cc:2212: pushl(dest_addr);
Some comments explaining what is going on here would be helpful.

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/flow_graph_co...
File runtime/vm/flow_graph_compiler_ia32.cc (right):

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/flow_graph_co...
runtime/vm/flow_graph_compiler_ia32.cc:1243: return VerifiedMemory::enabled() ?
50 : 4;
This looks like an arbitrary number. How does one know to update this if the
number of instructions or the encoding changes?

[koda, 2014-11-17 16:17:11]

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
File runtime/vm/assembler_ia32.cc (right):

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
runtime/vm/assembler_ia32.cc:2208: void Assembler::Verify(const Address& dest) {
On 2014/11/14 22:09:11, Ivan Posva wrote:
> Verify is a bit too generic a name for this functionality.

Renamed to VerifyHeapWord.

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/assembler_ia3...
runtime/vm/assembler_ia32.cc:2212: pushl(dest_addr);
On 2014/11/14 22:09:11, Ivan Posva wrote:
> Some comments explaining what is going on here would be helpful.

Done. Also improved naming of vars/params.

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/flow_graph_co...
File runtime/vm/flow_graph_compiler_ia32.cc (right):

https://codereview.chromium.org/721233002/diff/20001/runtime/vm/flow_graph_co...
runtime/vm/flow_graph_compiler_ia32.cc:1243: return VerifiedMemory::enabled() ?
50 : 4;
On 2014/11/14 22:09:11, Ivan Posva wrote:
> This looks like an arbitrary number. How does one know to update this if the
> number of instructions or the encoding changes?

In debug mode, the ASSERT above will fail immediately (and in release mode,
CodePatcher will very likely crash).

Added more explicit instructions, and an explanation why the number must be
constant across all code in an isolate (due to its use by CodePatcher).

[koda, 2014-11-17 16:49:44]

Committed patchset #3 (id:40001) manually as r41785 (presubmit successful).