On Fri, Jul 25, 2014 at 1:27 PM, Richard Biener <richard.guent...@gmail.com> wrote: > On Thu, Jul 17, 2014 at 11:07 AM, Bin Cheng <bin.ch...@arm.com> wrote: >> Hi, >> This is a series of three patches improving induction variable elimination. >> Currently GCC only eliminates iv for very specific case when the loop's >> latch could run zero times, i.e., when may_be_zero field of loop niter >> information evaluates to true. In fact, it's so specific that >> iv_elimination_compare_lt rarely succeeds during either GCC bootstrap or >> spec2000/spec2006 compilation. Though intrusive data shows these patches >> don't help iv elimination that much for GCC bootstrap, they do capture >> 5%~15% more eliminations for compiling spec2000/2006. Detailed numbers are >> like: >> 2k/int 2k/fp 2k6/int 2k6/fp >> improve ~9.6% ~4.8% ~5.5% ~14.4% >> >> All patches pass bootstrap and regression test on x86_64/x86. I will >> bootstrap and test them on aarch64/arm platforms too. >> >> The first patch turns to tree operand_equal_p to check the number of >> iterations in iv_elimination_lt. Though I think this change isn't necessary >> for current code, it's needed if we further relax iv elimination for cases >> in which sign/unsigned conversion is involved. > > As said elsewhere this bug should be fixed in tree-affine.c. Do you have > a testcase? > Sorry I don't have test case without patching GCC, I will revisit the problem and try to understand whether it's necessary or in which part it should be fixed.
Thanks, bin
