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Make fix for PR 83965 handle SLP reduction chains

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This patch prevents pattern-matching of fold-left SLP reduction chains,
which the previous patch for 83965 didn't handle properly.  It only
stops the last statement in the group from being matched, but that's
enough to cause the group to be dissolved later.

A better fix would be to put all the information about the reduction
on the the first statement in the reduction chain, so that every
statement in the group can tell what the group is doing.  That doesn't
seem like stage 4 material though.

2018-02-26  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/83965
	* tree-vect-patterns.c (vect_reassociating_reduction_p): Assume
	that grouped statements are part of a reduction chain.  Return
	true if the statement is not marked as a reduction itself but
	is part of a group.
	(vect_recog_dot_prod_pattern): Don't check whether the statement
	is part of a group here.
	(vect_recog_sad_pattern): Likewise.
	(vect_recog_widen_sum_pattern): Likewise.

gcc/testsuite/
	PR tree-optimization/83965
	* gcc.dg/vect/pr83965-2.c: New test.

From-SVN: r257995
This commit is contained in:
Richard Sandiford 2018-02-26 16:17:00 +00:00 committed by Richard Sandiford
parent 9992661cc6
commit d99dcb77bb
4 changed files with 41 additions and 8 deletions
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12
gcc/ChangeLog
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@ -1,3 +1,15 @@
2018-02-26 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/83965
* tree-vect-patterns.c (vect_reassociating_reduction_p): Assume
that grouped statements are part of a reduction chain. Return
true if the statement is not marked as a reduction itself but
is part of a group.
(vect_recog_dot_prod_pattern): Don't check whether the statement
is part of a group here.
(vect_recog_sad_pattern): Likewise.
(vect_recog_widen_sum_pattern): Likewise.
2018-02-26 Eric Botcazou <ebotcazou@adacore.com>
PR debug/84545

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-02-26 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/83965
* gcc.dg/vect/pr83965-2.c: New test.
2018-02-26 Tom de Vries <tom@codesourcery.com>
* gcc.c-torture/compile/regs-arg-size.c (swprintf): Declare.

16
gcc/testsuite/gcc.dg/vect/pr83965-2.c Normal file
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@ -0,0 +1,16 @@
/* { dg-do compile } */
/* { dg-additional-options "-Ofast -ftrapv" } */
int c;
unsigned char d;
int e (unsigned char *f)
{
int g;
for (int a; a; a++)
{
for (int b = 0; b < 6; b++)
g += __builtin_abs (f[b] - d);
f += c;
}
return g;
}

16
gcc/tree-vect-patterns.c
View File

@ -222,13 +222,16 @@ vect_recog_temp_ssa_var (tree type, gimple *stmt)
}
/* Return true if STMT_VINFO describes a reduction for which reassociation
is allowed. */
is allowed. If STMT_INFO is part of a group, assume that it's part of
a reduction chain and optimistically assume that all statements
except the last allow reassociation. */
static bool
vect_reassociating_reduction_p (stmt_vec_info stmt_vinfo)
{
return (STMT_VINFO_DEF_TYPE (stmt_vinfo) == vect_reduction_def
&& STMT_VINFO_REDUC_TYPE (stmt_vinfo) != FOLD_LEFT_REDUCTION);
? STMT_VINFO_REDUC_TYPE (stmt_vinfo) != FOLD_LEFT_REDUCTION
: GROUP_FIRST_ELEMENT (stmt_vinfo) != NULL);
}
/* Function vect_recog_dot_prod_pattern
@ -350,8 +353,7 @@ vect_recog_dot_prod_pattern (vec<gimple *> *stmts, tree *type_in,
{
gimple *def_stmt;
if (!vect_reassociating_reduction_p (stmt_vinfo)
&& ! STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_vinfo))
if (!vect_reassociating_reduction_p (stmt_vinfo))
return NULL;
oprnd0 = gimple_assign_rhs1 (last_stmt);
oprnd1 = gimple_assign_rhs2 (last_stmt);
@ -571,8 +573,7 @@ vect_recog_sad_pattern (vec<gimple *> *stmts, tree *type_in,
{
gimple *def_stmt;
if (!vect_reassociating_reduction_p (stmt_vinfo)
&& ! STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_vinfo))
if (!vect_reassociating_reduction_p (stmt_vinfo))
return NULL;
plus_oprnd0 = gimple_assign_rhs1 (last_stmt);
plus_oprnd1 = gimple_assign_rhs2 (last_stmt);
@ -1256,8 +1257,7 @@ vect_recog_widen_sum_pattern (vec<gimple *> *stmts, tree *type_in,
if (gimple_assign_rhs_code (last_stmt) != PLUS_EXPR)
return NULL;
if (!vect_reassociating_reduction_p (stmt_vinfo)
&& ! STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_vinfo))
if (!vect_reassociating_reduction_p (stmt_vinfo))
return NULL;
oprnd0 = gimple_assign_rhs1 (last_stmt);