[SH] Add simple_return pattern

[Christian Bruel]

Hi Kaz,

The failure turned out to be issues with the profile count and handling
or region partitioning. So, I prefer to handle those separately,
For now, I disable shrink-wrap when partitioning, even if the problem
seems to have disappeared with the more constrained heuristics. This is
probably latent also on other targets BTW.

I added a sh_can_use_simple_return_p function that makes the heuristic
refinements more convenient. For instance, measured that shrink-wrap is
generally not good when optimizing for size because we might introduce
new return instructions or split blocks to avoid the epilogue, that is
still in the code somewhere anyway.

Cycle-accurate benchmarks show a few very small improvements (there and
there, about max 2%. accordingly, the prologue is rarely in the critical
path...) but no regression. Manual assembly peering of CSiBE show that
the transformation are decent.

Checked with all assertions this time, Candidate for trunk.

Many thanks

Christian


On 09/11/2012 03:05 AM, Kaz Kojima wrote:
> Christian Bruel <christian.bruel@st.com> wrote:
>> This patch implements the simple_return pattern to enable -fshrink-wrap
>> on SH. It also clean up some redundancies for expand_epilogue (called
>> twice from the "return" and "epilogue" patterns and the
>> sh_expand_prologue parameter type.
>>
>> No regressions with sh-superh-elf and sh4-linux gcc testsuites.
> 
> With the patch + revision 191106, I've got a new failure:
> 
> FAIL: gcc.dg/tree-prof/bb-reorg.c compilation,  -fprofile-use -D_PROFILE_USE (internal compiler error)
> 
> for sh4-unknown-linux-gnu.  My testsuite/gcc/gcc.log says
> 
> /exp/ldroot/dodes/xsh-gcc/gcc/xgcc -B/exp/ldroot/dodes/xsh-gcc/gcc/ /exp/ldroot/dodes/LOCAL/trunk/gcc/testsuite/gcc.dg/tree-prof/bb-reorg.c -fno-diagnostics-show-caret -O2 -freorder-blocks-and-partition -fprofile-use -D_PROFILE_USE -lm -o /exp/ldroot/dodes/xsh-gcc/gcc/testsuite/gcc/bb-reorg.x02
> /exp/ldroot/dodes/LOCAL/trunk/gcc/testsuite/gcc.dg/tree-prof/bb-reorg.c: In function 'main':
> /exp/ldroot/dodes/LOCAL/trunk/gcc/testsuite/gcc.dg/tree-prof/bb-reorg.c:38:1: error: EDGE_CROSSING missing across section boundary
> /exp/ldroot/dodes/LOCAL/trunk/gcc/testsuite/gcc.dg/tree-prof/bb-reorg.c:38:1: internal compiler error: verify_flow_info failed
> Please submit a full bug report,
> 
> Regards,
> 	kaz
> 
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