* [PATCH] Fix associate_plusminus A + ~A optimization (PR tree-optimization/48717)
@ 2011-04-22 14:49 Jakub Jelinek
2011-04-22 15:21 ` Richard Guenther
0 siblings, 1 reply; 3+ messages in thread
From: Jakub Jelinek @ 2011-04-22 14:49 UTC (permalink / raw)
To: gcc-patches
Hi!
On the following testcase associate_plusminus optimizes
A + ~A into INTEGER_CST { -1, -1 } with type unsigned short, which
confuses enough following passes on (int) cast of that into
assuming it is -1 instead of 65535.
Fixed by using build_int_cst_type, which is what e.g. fold-const.c
uses when optimizing X + ~X.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
and 4.6 (where the bug is just latent)? 4.5 didn't have
associate_plusminus.
2011-04-22 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/48717
* tree-ssa-forwprop.c (associate_plusminus): For A + ~A and
~A + A optimizations use build_int_cst_type instead of build_int_cst.
* gcc.c-torture/execute/pr48717.c: New test.
--- gcc/tree-ssa-forwprop.c.jj 2011-04-01 23:09:21.000000000 +0200
+++ gcc/tree-ssa-forwprop.c 2011-04-22 11:57:10.000000000 +0200
@@ -1815,7 +1815,7 @@ associate_plusminus (gimple stmt)
{
/* ~A + A -> -1. */
code = INTEGER_CST;
- rhs1 = build_int_cst (TREE_TYPE (rhs2), -1);
+ rhs1 = build_int_cst_type (TREE_TYPE (rhs2), -1);
rhs2 = NULL_TREE;
gimple_assign_set_rhs_with_ops (&gsi, code, rhs1, NULL_TREE);
gcc_assert (gsi_stmt (gsi) == stmt);
@@ -1915,7 +1915,7 @@ associate_plusminus (gimple stmt)
{
/* A + ~A -> -1. */
code = INTEGER_CST;
- rhs1 = build_int_cst (TREE_TYPE (rhs1), -1);
+ rhs1 = build_int_cst_type (TREE_TYPE (rhs1), -1);
rhs2 = NULL_TREE;
gimple_assign_set_rhs_with_ops (&gsi, code, rhs1, NULL_TREE);
gcc_assert (gsi_stmt (gsi) == stmt);
--- gcc/testsuite/gcc.c-torture/execute/pr48717.c.jj 2011-04-22 11:59:23.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/execute/pr48717.c 2011-04-22 11:58:48.000000000 +0200
@@ -0,0 +1,26 @@
+/* PR tree-optimization/48717 */
+
+extern void abort (void);
+
+int v = 1, w;
+
+unsigned short
+foo (unsigned short x, unsigned short y)
+{
+ return x + y;
+}
+
+void
+bar (void)
+{
+ v = foo (~w, w);
+}
+
+int
+main ()
+{
+ bar ();
+ if (v != (unsigned short) -1)
+ abort ();
+ return 0;
+}
Jakub
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Fix associate_plusminus A + ~A optimization (PR tree-optimization/48717)
2011-04-22 14:49 [PATCH] Fix associate_plusminus A + ~A optimization (PR tree-optimization/48717) Jakub Jelinek
@ 2011-04-22 15:21 ` Richard Guenther
2011-04-22 19:26 ` Jakub Jelinek
0 siblings, 1 reply; 3+ messages in thread
From: Richard Guenther @ 2011-04-22 15:21 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On Fri, Apr 22, 2011 at 3:41 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> On the following testcase associate_plusminus optimizes
> A + ~A into INTEGER_CST { -1, -1 } with type unsigned short, which
> confuses enough following passes on (int) cast of that into
> assuming it is -1 instead of 65535.
Ick.
> Fixed by using build_int_cst_type, which is what e.g. fold-const.c
> uses when optimizing X + ~X.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
> and 4.6 (where the bug is just latent)? 4.5 didn't have
> associate_plusminus.
Ok for both.
build_int_cst looks seriously broken, I think we want to make it
an alias of build_int_cst_type, or rather call that from
build_int_cst.
Thanks,
Richard.
> 2011-04-22 Jakub Jelinek <jakub@redhat.com>
>
> PR tree-optimization/48717
> * tree-ssa-forwprop.c (associate_plusminus): For A + ~A and
> ~A + A optimizations use build_int_cst_type instead of build_int_cst.
>
> * gcc.c-torture/execute/pr48717.c: New test.
>
> --- gcc/tree-ssa-forwprop.c.jj 2011-04-01 23:09:21.000000000 +0200
> +++ gcc/tree-ssa-forwprop.c 2011-04-22 11:57:10.000000000 +0200
> @@ -1815,7 +1815,7 @@ associate_plusminus (gimple stmt)
> {
> /* ~A + A -> -1. */
> code = INTEGER_CST;
> - rhs1 = build_int_cst (TREE_TYPE (rhs2), -1);
> + rhs1 = build_int_cst_type (TREE_TYPE (rhs2), -1);
> rhs2 = NULL_TREE;
> gimple_assign_set_rhs_with_ops (&gsi, code, rhs1, NULL_TREE);
> gcc_assert (gsi_stmt (gsi) == stmt);
> @@ -1915,7 +1915,7 @@ associate_plusminus (gimple stmt)
> {
> /* A + ~A -> -1. */
> code = INTEGER_CST;
> - rhs1 = build_int_cst (TREE_TYPE (rhs1), -1);
> + rhs1 = build_int_cst_type (TREE_TYPE (rhs1), -1);
> rhs2 = NULL_TREE;
> gimple_assign_set_rhs_with_ops (&gsi, code, rhs1, NULL_TREE);
> gcc_assert (gsi_stmt (gsi) == stmt);
> --- gcc/testsuite/gcc.c-torture/execute/pr48717.c.jj 2011-04-22 11:59:23.000000000 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/pr48717.c 2011-04-22 11:58:48.000000000 +0200
> @@ -0,0 +1,26 @@
> +/* PR tree-optimization/48717 */
> +
> +extern void abort (void);
> +
> +int v = 1, w;
> +
> +unsigned short
> +foo (unsigned short x, unsigned short y)
> +{
> + return x + y;
> +}
> +
> +void
> +bar (void)
> +{
> + v = foo (~w, w);
> +}
> +
> +int
> +main ()
> +{
> + bar ();
> + if (v != (unsigned short) -1)
> + abort ();
> + return 0;
> +}
>
> Jakub
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Fix associate_plusminus A + ~A optimization (PR tree-optimization/48717)
2011-04-22 15:21 ` Richard Guenther
@ 2011-04-22 19:26 ` Jakub Jelinek
0 siblings, 0 replies; 3+ messages in thread
From: Jakub Jelinek @ 2011-04-22 19:26 UTC (permalink / raw)
To: Richard Guenther; +Cc: gcc-patches
On Fri, Apr 22, 2011 at 04:50:26PM +0200, Richard Guenther wrote:
> build_int_cst looks seriously broken, I think we want to make it
> an alias of build_int_cst_type, or rather call that from
> build_int_cst.
The comment above build_int_cst_type talks about it:
"We cannot however make this a default behavior of build_int_cst without
more intrusive changes, since there are parts of gcc that rely on the
extra precision of the integer constants."
Jakub
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-04-22 14:49 [PATCH] Fix associate_plusminus A + ~A optimization (PR tree-optimization/48717) Jakub Jelinek
2011-04-22 15:21 ` Richard Guenther
2011-04-22 19:26 ` Jakub Jelinek
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