Hi,
The previous fix for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77916
ensured that record_increment would use normal multiplier initializers
for increments of -1 with unknown strides, just as for all other negative
increments. However, we still had a problem in insert_initializers wherein
the test for whether the replacement will need a POINTER_PLUS_EXPR was not
accurate. This patch fixes this, and again removes the stopgap solution
so that we can process -1 increments with pointer types.
Markus Trippelsdorf kindly tested all of the ffmpeg code on x86_64 with
-march=amdfam10 to ensure there are no more of these issues lurking there.
That has been a fertile environment for these kinds of negative pointer
increments.
Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no new
regressions, committed.
Thanks,
Bill
2016-10-19 Bill Schmidt <wschm...@linux.vnet.ibm.com>
PR tree-optimization/77916
PR tree-optimization/77937
* gimple-ssa-strength-reduction.c (analyze_increments): Remove
stopgap fix.
(insert_initializers): Requirement of initializer for -1 should be
based on pointer-typedness of the candidate basis.
Index: gcc/gimple-ssa-strength-reduction.c
===================================================================
--- gcc/gimple-ssa-strength-reduction.c (revision 241305)
+++ gcc/gimple-ssa-strength-reduction.c (working copy)
@@ -2825,10 +2825,6 @@ analyze_increments (slsr_cand_t first_dep, machine
&& !POINTER_TYPE_P (first_dep->cand_type)))
incr_vec[i].cost = COST_NEUTRAL;
- /* FIXME: Still having trouble with pointers with a -1 increment. */
- else if (incr == -1 && POINTER_TYPE_P (first_dep->cand_type))
- incr_vec[i].cost = COST_INFINITE;
-
/* FORNOW: If we need to add an initializer, give up if a cast from
the candidate's type to its stride's type can lose precision.
This could eventually be handled better by expressly retaining the
@@ -3115,7 +3111,7 @@ insert_initializers (slsr_cand_t c)
if (!profitable_increment_p (i)
|| incr == 1
|| (incr == -1
- && gimple_assign_rhs_code (c->cand_stmt) != POINTER_PLUS_EXPR)
+ && (!POINTER_TYPE_P (lookup_cand (c->basis)->cand_type)))
|| incr == 0)
continue;
