> -----Original Message----- > From: Jeff Law [mailto:l...@redhat.com] > Sent: Friday, October 11, 2013 1:20 PM > To: Zhenqiang Chen > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [PATCH] Reassociate X == CST1 || X == CST2 if popcount (CST2 - > CST1) == 1 into ((X - CST1) & ~(CST2 - CST1)) == 0 > > On 10/10/13 03:25, Zhenqiang Chen wrote: > > > > > It comes from Coremark. The code is: > > > > if (NEXT_SYMBOL == '+' || NEXT_SYMBOL == '-') > I should have guessed ;-) > > > > > > For ARM, there are three instructions rather than 4 (in thumb state). > > For some older gcc, I got performance improvement on ARM chromebook. > > But I can not reproduce the performance gain now. > > > > I will collect logs during GCC bootstrap. > Thanks. It doesn't have to be anything particularly complex. When I'm > looking at a transformation I usually just put a printf when it triggers and grep > for the string in a make log.
Thanks. I check the make log. There are 1906 occurrences. > Depending on what I'm doing, I may dig more deeply into the situations > where its triggering to make sure I fully understand the primary and > secondary effects of a transformation which often leads to tweaking the > implementation. I don't think that level of rigor is needed here. > > Jeff >
