| Message ID | 20130116161346.GB3955@kam.mff.cuni.cz |
|---|---|
| State | New |
| Headers | show |
On Wed, Jan 16, 2013 at 5:13 PM, Jan Hubicka <hubicka@ucw.cz> wrote: > Hi, > this patch fixes ICE seen in PR51083 on PPC. Here the flags ^= 0x80000000 expression > is translated as PLUS. This makes us to consider flags to be IV and work out that the > loop do not really iterate. It is a missed optimization that we do not work out this > on all targets and do not unloop the loop at tree level. I opened PR for this. > This patch fixes the ICE that we get confused on concluding that max number of iterations > is 0. > > Bootstrapped/regtested x86_64-linux (where the code path do not really trigger obviously) > and tested that it is fixing the testcase on PPC. > OK? Ok. Thanks, Richard. > Honza > PR tree-optimizatoin/51083 > > * gcc.c-torture/compile/pr51083.c: New testcase. > > * loop-iv.c (iv_number_of_iterations): Consider zero iteration case. > > Index: testsuite/gcc.c-torture/compile/pr51083.c > =================================================================== > --- testsuite/gcc.c-torture/compile/pr51083.c (revision 0) > +++ testsuite/gcc.c-torture/compile/pr51083.c (revision 0) > @@ -0,0 +1,18 @@ > +extern int debug_threads; > +extern void sigsuspend (void); > +void my_waitpid (int flags, int wnohang) > +{ > + while (1) > + { > + if (flags & 0x80000000) > + { > + if (wnohang) > + break; > + if (debug_threads) > + __builtin_puts ("blocking\n"); > + sigsuspend (); > + } > + flags ^= 0x80000000; > + } > +} > + > Index: loop-iv.c > =================================================================== > --- loop-iv.c (revision 195144) > +++ loop-iv.c (working copy) > @@ -2819,7 +2819,8 @@ iv_number_of_iterations (struct loop *lo > else > { > max = determine_max_iter (loop, desc, old_niter); > - gcc_assert (max); > + if (!max) > + goto zero_iter_simplify; > if (!desc->infinite > && !desc->assumptions) > record_niter_bound (loop, double_int::from_uhwi (max),
Index: testsuite/gcc.c-torture/compile/pr51083.c =================================================================== --- testsuite/gcc.c-torture/compile/pr51083.c (revision 0) +++ testsuite/gcc.c-torture/compile/pr51083.c (revision 0) @@ -0,0 +1,18 @@ +extern int debug_threads; +extern void sigsuspend (void); +void my_waitpid (int flags, int wnohang) +{ + while (1) + { + if (flags & 0x80000000) + { + if (wnohang) + break; + if (debug_threads) + __builtin_puts ("blocking\n"); + sigsuspend (); + } + flags ^= 0x80000000; + } +} + Index: loop-iv.c =================================================================== --- loop-iv.c (revision 195144) +++ loop-iv.c (working copy) @@ -2819,7 +2819,8 @@ iv_number_of_iterations (struct loop *lo else { max = determine_max_iter (loop, desc, old_niter); - gcc_assert (max); + if (!max) + goto zero_iter_simplify; if (!desc->infinite && !desc->assumptions) record_niter_bound (loop, double_int::from_uhwi (max),