Subzero: Control memory growth from local label fixups.

Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the Assembler arena, and are no longer pooled, which restricts the memory growth from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active, these fixups have to be fixed up by holding a pointer to the symbol rather than the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB as before.

This also partially fixes an existing bug with arm32/nonsfi/iasm, exposed by running cross tests and forcing iasm output.

BUG= none
R=jpp@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=3e324002a1df4861c389f7289ead7e9ff5adcd42

[Jim Stichnoth, 2016-03-08 07:54:24]

Description was changed from

==========
Subzero: Control memory growth from local label fixups.

BUG= none
==========

to

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

BUG= none
==========

[Jim Stichnoth, 2016-03-08 07:54:24]

stichnot@chromium.org changed reviewers:
+ eholk@chromium.org, jpp@chromium.org, kschimpf@google.com, sehr@chromium.org

[Jim Stichnoth, 2016-03-08 07:57:00]

Description was changed from

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

BUG= none
==========

to

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB
as before.

BUG= none
==========

[Jim Stichnoth, 2016-03-08 14:49:45]

A couple extra notes to give more context on the direction I still want to take
this.

1. ELF fixups and symbols are managed using a lot of std::string
objects/operations.  In a MINIMAL build, we should only use explicit strings for
externally visible symbols.  In other cases, we can use unique integer values
instead of strings as keys.

2. The ELF symbol table is represented as a std::map of symbols (using
std::string as the key).  It would be better to use unordered_map, and
optionally sort it before emission for deterministic behavior across STL
implementations.  (FWIW, change to unordered_map compiles, but generates
incorrect code; more investigation needed.)

[Jim Stichnoth, 2016-03-09 00:08:22]

Description was changed from

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB
as before.

BUG= none
==========

to

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB
as before.

This also partially fixes an existing bug with arm32/nonsfi/iasm, exposed by
running cross tests and forcing iasm output.

BUG= none
==========

[Jim Stichnoth, 2016-03-09 00:09:57]

PTAL

[John, 2016-03-09 00:12:45]

lgtm

[Jim Stichnoth, 2016-03-09 00:18:43]

Description was changed from

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB
as before.

This also partially fixes an existing bug with arm32/nonsfi/iasm, exposed by
running cross tests and forcing iasm output.

BUG= none
==========

to

==========
Subzero: Control memory growth from local label fixups.

The ConstantRelocatable objects for pushing local labels are allocated from the
Assembler arena, and are no longer pooled, which restricts the memory growth
from sandboxing x86-64 calls.

Because the Assembler arena is destroyed while the fixups are still active,
these fixups have to be fixed up by holding a pointer to the symbol rather than
the constant.

On the 10MB test pexe, the overall growth by the end is ~20MB, instead of ~130MB
as before.

This also partially fixes an existing bug with arm32/nonsfi/iasm, exposed by
running cross tests and forcing iasm output.

BUG= none
R=jpp@chromium.org

Committed:
https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a...
==========

[Jim Stichnoth, 2016-03-09 00:18:45]

Committed patchset #3 (id:40001) manually as
3e324002a1df4861c389f7289ead7e9ff5adcd42 (presubmit successful).