On 05/30/2015 03:57 AM, Marc Glisse wrote:
On Fri, 29 May 2015, Jeff Law wrote:
c-common.c::shorten_compare has code to canonicalize the arguments of
a comparison so that the constant is the second argument. This patch
removes the implementation from c-common.c and instead implements it
in match.pd.
Note the match.pd tries to match the prior behavior of
shorten_compare, hence the strange handling of zero. No justification
exists AFAIK for that strange handling in shorten_compare.
The match.pd pattern is primarily Kai's -- I just took the 4 patterns
he wrote and squashed them into a single pattern to avoid the test
duplication.
The xfailed testcase is only case I saw across my comparison tests
where this change regressed. Basically shorten-compare had something
non-canonical when called. It was able to canonicalize, then optimize
the result. I just wanted a record of that test in the testsuite.
Obviously if we hit our goal of implementing everything from
shorten_compare, that test will no longer need to be xfailed :-)
Bootstrapped and regression tested on x86-linux-gnu. OK for the trunk?
I understand doing it in 2 commits to better see what regresses, but I
don't think we should keep the weirdness in match.pd.
Does it regress anything if we instead add inside the for loop that
follows /* -A CMP -B -> B CMP A. */
(simplify
(cmp CONSTANT_CLASS_P@0 @1)
(scmp @1 @0))
Nothing regresses compared to the version I posted with the distinct
patterns for canonicalization in my tests. This seems the cleanest, so
I'm going to spin it as a patch and repost.
Thanks for the suggestion,
jeff
