== This week ==
* cfgloop.h flatten (2/10)
- Rebased and tested on top of Andrew's patch
- bootstrapped on x86_64-unknown-linux-gnu
- building on all targets in config-list.mk in progress
* TCWG-777 (2/10)
- Problem is still present on trunk
- Original test-case: http://pastebin.com/UTv8g3aA
- Original test-case assembly for -O1: http://pastebin.com/815TgDjV
- Possibly reduced test-case: http://pastebin.com/UGUteX4a
- Assembly for reduced test-case for -O1: http://pastebin.com/edKu6CxH
- x86 assembly for reduced test-case for -O1: http://pastebin.com/9APbJeLr
- Workaround: To disable CSE in branch conditions make flags volatile.
This prevents
storing result of ands to temporary but leads to worse code-gen.
- Possible approaches from (https://bugs.launchpad.net/gcc-linaro/+bug/851258):
a) teach PRE not to fold in such cases ? I don't know how.
b) Write a new tree-ssa pass that "unfolds" cse on result of test conditions.
Check if operand in if (operand != 0) is a result of test condition.
eg:
_8 = flags & 1;
if (_8 != 0)
goto true_branch
else
goto false_branch
In this case we could add an attribute to _8 say "unfold".
If we again come across if (_8 != 0) at a later point,
and it's marked with "unfold",
we can create a new ssa var with definition of _8.
so it becomes:
_9 = flags & 1;
if (_9 != 0)
...
which will "undo" CSE on test conditions.
Does this sounds reasonable ?
Should we do it on all test conditions ?
I don't understand "suitable compare insn" a target should have in above link.
* TCWG-145 (2/10)
- Optimization is already implemented in PRE pass.
- Verified for various test-cases in eembc.
- Currently gcc does not convert global statics to locals
- remove-local-statics-7.c not handled currently by gcc:
(https://gcc.gnu.org/ml/gcc-patches/2008-07/msg01007.html)
- Desirable to have ipa dead-store analysis to avoid stores to static vars:
https://gcc.gnu.org/ml/gcc-patches/2008-07/msg01609.html
https://gcc.gnu.org/ml/gcc-patches/2008-07/msg01602.html
- continuing to look for cases where static-to-locals wins over PRE.
* Misc (4/10)
- Built firefox on x86 non-LTO
- Read thru tree-ssa-dse.c, IPA, LTO doc
- US Visa application
- Setting up home office
== Issues ==
Not able to connect to #linaro-tcwg thru ircproxy.linaro.org , password invalid.
== Next Week ==
- TCWG-830
- TCWG-835
- TCWG-844
- continue investigating branch out of range error issue.
- Work towards committing cfgloop.h patch