OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

PR81815: Invalid conditional reduction

Browse Source 
We weren't checking whether the phi in a conditional reduction was
used by the condition itself (which isn't a case we handle).

2017-08-11  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/81835
	* tree-vect-loop.c (vect_is_simple_reduction): Simply checks for
	the phi SSA_NAME.  Check that the condition in a COND_EXPR does
	not depend on the phi.

gcc/testsuite/
	PR tree-optimization/81835
	* gcc.dg/vect/pr81815.c: New test.

From-SVN: r251117
This commit is contained in:
Richard Sandiford 2017-08-16 07:51:13 +00:00 committed by Richard Sandiford
parent 60e095de00
commit 963aeaad25
4 changed files with 50 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2017-08-16 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/81835
* tree-vect-loop.c (vect_is_simple_reduction): Simply checks for
the phi SSA_NAME. Check that the condition in a COND_EXPR does
not depend on the phi.
2017-08-16 Alan Modra <amodra@gmail.com>
* config/rs6000/rs6000.c (rs6000_init_hard_regno_mode_ok): Delete

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2017-08-16 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/81835
* gcc.dg/vect/pr81815.c: New test.
2017-08-15 Joseph Myers <joseph@codesourcery.com>
PR target/78460

26
gcc/testsuite/gcc.dg/vect/pr81815.c Normal file
View File

@ -0,0 +1,26 @@
/* { dg-do run } */
int __attribute__ ((noinline, noclone))
f (int *x, int n)
{
int b = 13;
for (int i = 0; i < n; ++i)
{
int next = x[i];
b = b < 100 ? next : 200;
}
return b;
}
static int res[32];
int
main (void)
{
for (int i = 0; i < 32; ++i)
res[i] = i;
res[15] = 100;
if (f (res, 32) != 200)
__builtin_abort ();
return 0;
}

19
gcc/tree-vect-loop.c
View File

@ -2690,15 +2690,15 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi,
*double_reduc = false;
*v_reduc_type = TREE_CODE_REDUCTION;
name = PHI_RESULT (phi);
tree phi_name = PHI_RESULT (phi);
/* ??? If there are no uses of the PHI result the inner loop reduction
won't be detected as possibly double-reduction by vectorizable_reduction
because that tries to walk the PHI arg from the preheader edge which
can be constant. See PR60382. */
if (has_zero_uses (name))
if (has_zero_uses (phi_name))
return NULL;
nloop_uses = 0;
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name)
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, phi_name)
{
gimple *use_stmt = USE_STMT (use_p);
if (is_gimple_debug (use_stmt))
@ -2847,10 +2847,7 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi,
simply rewriting this into "res += -x[i]". Avoid changing
gimple instruction for the first simple tests and only do this
if we're allowed to change code at all. */
if (code == MINUS_EXPR
&& ! ((op1 = gimple_assign_rhs2 (def_stmt))
&& TREE_CODE (op1) == SSA_NAME
&& SSA_NAME_DEF_STMT (op1) == phi))
if (code == MINUS_EXPR && gimple_assign_rhs2 (def_stmt) != phi_name)
code = PLUS_EXPR;
if (code == COND_EXPR)
@ -2864,6 +2861,14 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi,
op4 = TREE_OPERAND (op3, 1);
op3 = TREE_OPERAND (op3, 0);
}
if (op3 == phi_name || op4 == phi_name)
{
if (dump_enabled_p ())
report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt,
"reduction: condition depends on previous"
" iteration: ");
return NULL;
}
op1 = gimple_assign_rhs2 (def_stmt);
op2 = gimple_assign_rhs3 (def_stmt);