Thanks. I'm going to wait until/if you approve the previous patch in the series before I commit:
[PATCH] Try to resolve paths in threader without looking further back. ..because otherwise I'll have to test again and twiddle tests in a different order. Aldy On Wed, Oct 20, 2021 at 8:04 PM Jeff Law <jeffreya...@gmail.com> wrote: > > > > On 10/20/2021 6:37 AM, Aldy Hernandez wrote: > > The code that threads incoming paths to a PHI is duplicating what we > > do generically in find_paths_to_names. This shortcoming is actually > > one of the reasons we aren't threading all possible paths into a PHI. > > For example, we give up after finding one threadable path, but some > > PHIs have multiple threadable paths: > > > > // x_5 = PHI <10(4), 20(5), ...> > > // if (x_5 > 5) > > > > Addressing this not only fixes the oversight, but simplifies the > > PHI handling code, since we can consider the PHI fully resolved upon > > return. > > > > Interestingly, for ssa-thread-12.c the main thread everything was > > hinging on was unreachable. With this patch, we call > > maybe_register_path() earlier. In doing so, the solver realizes > > that any path starting with 4->8 is unreachable and can be avoided. > > This caused the cascade of threadable paths that depended on this > > to no longer happen. Since threadable paths in thread[34] was the only > > thing this test was testing, there's no longer anything to test. Neat! > > > > Tested on x86-64 Linux. > > > > OK for trunk? > > > > gcc/ChangeLog: > > > > * tree-ssa-threadbackward.c (back_threader::resolve_phi): > > Attempt to resolve all incoming paths to a PHI. > > (back_threader::resolve_def): Always return true for PHIs. > > > > gcc/testsuite/ChangeLog: > > > > * gcc.dg/tree-ssa/pr21090.c: Adjust for threading. > > * gcc.dg/tree-ssa/ssa-thread-12.c: Removed. > OK > jeff >
