Subzero: Tweaks to reduce malloc use.

Subzero: Tweaks to reduce malloc use.

1. Subzero constructs many strings based in part on function name.  When function names are not present (as in properly finalized pexes), they are synthesized as something like "Function12345".  We can shorten these strings to e.g. "F12345" by using --default-function-prefix=F .  Similar for global variable names.

Using short strings makes it much less likely to have to use malloc.  As such, we force that to be the default in the browser translator build.  For perf-testing the command-line version, the user can just add the option manually for now.

Ultimately, we should avoid use of strings in this way.

2. The register allocator uses a few instances of llvm::SmallVector that are sized too small and therefore end up using malloc.  This can be fixed in a clean way, and there is a TODO for it, but in the meantime we just bump the size.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4360
R=jpp@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=843142fe0c5913df2391f9ac4608a02c038953cb

[Jim Stichnoth, 2016-03-09 23:12:38]

Description was changed from

==========
Subzero: Tweaks to reduce malloc use.

BUG=
==========

to

==========
Subzero: Tweaks to reduce malloc use.

1. Subzero constructs many strings based in part on function name.  When
function names are not present (as in properly finalized pexes), they are
synthesized as something like "Function12345".  We can shorten these strings to
e.g. "F12345" by using --default-function-prefix=F .  Similar for global
variable names.

Using short strings makes it much less likely to have to use malloc.  As such,
we force that to be the default in the browser translator build.  For
perf-testing the command-line version, the user can just add the option manually
for now.

Ultimately, we should avoid use of strings in this way.

2. The register allocator uses a few instances of llvm::SmallVector that are
sized too small and therefore end up using malloc.  This can be fixed in a clean
way, and there is a TODO for it, but in the meantime we just bump the size.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4360
==========

[Jim Stichnoth, 2016-03-09 23:12:38]

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

[John, 2016-03-09 23:15:41]

lgtm

https://codereview.chromium.org/1776343004/diff/1/src/IceRegAlloc.h
File src/IceRegAlloc.h (right):

https://codereview.chromium.org/1776343004/diff/1/src/IceRegAlloc.h#newcode71
src/IceRegAlloc.h:71: llvm::SmallVector<RegWeight, REGS_SIZE> Weights;
Perhaps change this to std::array?

[Jim Stichnoth, 2016-03-09 23:19:32]

https://codereview.chromium.org/1776343004/diff/1/src/IceRegAlloc.h
File src/IceRegAlloc.h (right):

https://codereview.chromium.org/1776343004/diff/1/src/IceRegAlloc.h#newcode71
src/IceRegAlloc.h:71: llvm::SmallVector<RegWeight, REGS_SIZE> Weights;
On 2016/03/09 23:15:41, John wrote:
> Perhaps change this to std::array?

I did try making that change, and also to the two other instances of
SmallVector.  This also required removing the resize() and reserve() calls, plus
do something special about the register randomization interface.  Then it failed
various tests so I decided to defer it until working on the cleaner solution.

[Jim Stichnoth, 2016-03-09 23:19:43]

Description was changed from

==========
Subzero: Tweaks to reduce malloc use.

1. Subzero constructs many strings based in part on function name.  When
function names are not present (as in properly finalized pexes), they are
synthesized as something like "Function12345".  We can shorten these strings to
e.g. "F12345" by using --default-function-prefix=F .  Similar for global
variable names.

Using short strings makes it much less likely to have to use malloc.  As such,
we force that to be the default in the browser translator build.  For
perf-testing the command-line version, the user can just add the option manually
for now.

Ultimately, we should avoid use of strings in this way.

2. The register allocator uses a few instances of llvm::SmallVector that are
sized too small and therefore end up using malloc.  This can be fixed in a clean
way, and there is a TODO for it, but in the meantime we just bump the size.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4360
==========

to

==========
Subzero: Tweaks to reduce malloc use.

1. Subzero constructs many strings based in part on function name.  When
function names are not present (as in properly finalized pexes), they are
synthesized as something like "Function12345".  We can shorten these strings to
e.g. "F12345" by using --default-function-prefix=F .  Similar for global
variable names.

Using short strings makes it much less likely to have to use malloc.  As such,
we force that to be the default in the browser translator build.  For
perf-testing the command-line version, the user can just add the option manually
for now.

Ultimately, we should avoid use of strings in this way.

2. The register allocator uses a few instances of llvm::SmallVector that are
sized too small and therefore end up using malloc.  This can be fixed in a clean
way, and there is a TODO for it, but in the meantime we just bump the size.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4360
R=jpp@chromium.org

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

[Jim Stichnoth, 2016-03-09 23:19:44]

Committed patchset #1 (id:1) manually as
843142fe0c5913df2391f9ac4608a02c038953cb (presubmit successful).