| Message ID | 59B92C58.6070204@foss.arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [store-merging] Use store order as tie-breaker in sort_by_bitpos | expand |
On Wed, Sep 13, 2017 at 3:02 PM, Kyrill Tkachov <kyrylo.tkachov@foss.arm.com> wrote: > Hi all, > > As Alexander pointed out in the thread starting at [1] the sort_by_bitpos > sorting function > was behaving badly when we had multiple stores at the same position. He > fixed that (thanks!) > but we can do better by not returning zero when the bitpositions are equal > but by falling back > to comparing the order the stores appear in, which is guaranteed to be > unique (barring other > bugs elsewhere). > > This patch does that. > > Bootstrapped and tested on aarch64-none-linux-gnu. > > Ok for trunk? Ok. Richard. > Thanks, > Kyrill > > [1] https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00895.html > > 2017-09-13 Kyrylo Tkachov <kyrylo.tkachov@arm.com> > > * gimple-ssa-store-merging.c (sort_by_bitpos): Compare store order > when bitposition is the same.
diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c index c60d56a..3260c56 100644 --- a/gcc/gimple-ssa-store-merging.c +++ b/gcc/gimple-ssa-store-merging.c @@ -521,7 +521,9 @@ sort_by_bitpos (const void *x, const void *y) else if ((*tmp)->bitpos > (*tmp2)->bitpos) return 1; else - return 0; + /* If they are the same let's use the order which is guaranteed to + be different. */ + return (*tmp)->order - (*tmp2)->order; } /* Sorting function for store_immediate_info objects.
Hi all, As Alexander pointed out in the thread starting at [1] the sort_by_bitpos sorting function was behaving badly when we had multiple stores at the same position. He fixed that (thanks!) but we can do better by not returning zero when the bitpositions are equal but by falling back to comparing the order the stores appear in, which is guaranteed to be unique (barring other bugs elsewhere). This patch does that. Bootstrapped and tested on aarch64-none-linux-gnu. Ok for trunk? Thanks, Kyrill [1] https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00895.html 2017-09-13 Kyrylo Tkachov <kyrylo.tkachov@arm.com> * gimple-ssa-store-merging.c (sort_by_bitpos): Compare store order when bitposition is the same.