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| author | Jeff Law <law@redhat.com> | 2017-01-15 02:34:01 -0700 |
|---|---|---|
| committer | Jeff Law <law@gcc.gnu.org> | 2017-01-15 02:34:01 -0700 |
| commit | 0cb4b758f5372ed1b5be14f79723ad59afba25f2 (patch) | |
| tree | c0cef117b1e3d8ee31f6df5a6028a19c1339a086 /gcc | |
| parent | 3d812e26eab44f72c6f047ea9a2b71dcbe009878 (diff) | |
| download | gcc-0cb4b758f5372ed1b5be14f79723ad59afba25f2.zip gcc-0cb4b758f5372ed1b5be14f79723ad59afba25f2.tar.gz gcc-0cb4b758f5372ed1b5be14f79723ad59afba25f2.tar.bz2 | |
re PR tree-optimization/79090 (DSE wrongly removes store at variable offset)
PR tree-optimization/79090
* tree-ssa-dse.c (valid_ao_ref_for_dse): Reject zero length and
variable length stores.
(compute_trims): Delete dead assignment to *trim_tail.
(dse_dom_walker::dse_optimize_stmt): Optimize mem* calls with
zero length.
From-SVN: r244472
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 9 | ||||
| -rw-r--r-- | gcc/tree-ssa-dse.c | 13 |
2 files changed, 21 insertions, 1 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 746f6af..36982c6 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,12 @@ +2017-01-14 Jeff Law <law@redhat.com> + + PR tree-optimization/79090 + * tree-ssa-dse.c (valid_ao_ref_for_dse): Reject zero length and + variable length stores. + (compute_trims): Delete dead assignment to *trim_tail. + (dse_dom_walker::dse_optimize_stmt): Optimize mem* calls with + zero length. + 2017-01-14 Bernd Schmidt <bschmidt@redhat.com> PR rtl-optimization/78626 diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c index 2e6f8ff..65dcb12 100644 --- a/gcc/tree-ssa-dse.c +++ b/gcc/tree-ssa-dse.c @@ -129,6 +129,8 @@ valid_ao_ref_for_dse (ao_ref *ref) { return (ao_ref_base (ref) && ref->max_size != -1 + && ref->size != 0 + && ref->max_size == ref->size && (ref->offset % BITS_PER_UNIT) == 0 && (ref->size % BITS_PER_UNIT) == 0 && (ref->size != -1)); @@ -221,7 +223,6 @@ compute_trims (ao_ref *ref, sbitmap live, int *trim_head, int *trim_tail) the REF to compute the trims. */ /* Now identify how much, if any of the tail we can chop off. */ - *trim_tail = 0; int last_orig = (ref->size / BITS_PER_UNIT) - 1; int last_live = bitmap_last_set_bit (live); *trim_tail = (last_orig - last_live) & ~0x1; @@ -700,6 +701,16 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi) case BUILT_IN_MEMMOVE: case BUILT_IN_MEMSET: { + /* Occasionally calls with an explicit length of zero + show up in the IL. It's pointless to do analysis + on them, they're trivially dead. */ + tree size = gimple_call_arg (stmt, 2); + if (integer_zerop (size)) + { + delete_dead_call (gsi); + return; + } + gimple *use_stmt; enum dse_store_status store_status; m_byte_tracking_enabled |