* [PATCH] tree-cfg: Allow enum types as result of POINTER_DIFF_EXPR [PR98556]
@ 2021-01-09 9:32 Jakub Jelinek
2021-01-09 9:45 ` Richard Biener
0 siblings, 1 reply; 2+ messages in thread
From: Jakub Jelinek @ 2021-01-09 9:32 UTC (permalink / raw)
To: Richard Biener; +Cc: gcc-patches
Hi!
As conversions between signed integers and signed enums with the same
precision are useless in GIMPLE, it seems strange that we require that
POINTER_DIFF_EXPR result must be INTEGER_TYPE.
If we really wanted to require that, we'd need to change the gimplifier
to ensure that, which it isn't the case on the following testcase.
What is going on during the gimplification is that when we have the
(enum T) (p - q) cast, it is stripped through
/* Strip away as many useless type conversions as possible
at the toplevel. */
STRIP_USELESS_TYPE_CONVERSION (*expr_p);
and when the MODIFY_EXPR is gimplified, the *to_p has enum T type,
while *from_p has intptr_t type and as there is no conversion in between,
we just create GIMPLE_ASSIGN from that.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-01-08 Jakub Jelinek <jakub@redhat.com>
PR c++/98556
* tree-cfg.c (verify_gimple_assign_binary): Allow lhs of
POINTER_DIFF_EXPR to be any integral type.
* c-c++-common/pr98556.c: New test.
--- gcc/tree-cfg.c.jj 2021-01-04 10:25:38.914232907 +0100
+++ gcc/tree-cfg.c 2021-01-08 15:57:41.605738398 +0100
@@ -3940,7 +3940,7 @@ verify_gimple_assign_binary (gassign *st
/* Because we special-case pointers to void we allow difference
of arbitrary pointers with the same mode. */
|| TYPE_MODE (rhs1_type) != TYPE_MODE (rhs2_type)
- || TREE_CODE (lhs_type) != INTEGER_TYPE
+ || !INTEGRAL_TYPE_P (lhs_type)
|| TYPE_UNSIGNED (lhs_type)
|| TYPE_PRECISION (lhs_type) != TYPE_PRECISION (rhs1_type))
{
--- gcc/testsuite/c-c++-common/pr98556.c.jj 2021-01-08 16:03:22.298900002 +0100
+++ gcc/testsuite/c-c++-common/pr98556.c 2021-01-08 16:03:07.715064312 +0100
@@ -0,0 +1,11 @@
+/* PR c++/98556 */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+enum T { E = -__LONG_MAX__ - 1 };
+
+enum T
+foo (char *p, char *q)
+{
+ return (enum T) (p - q);
+}
Jakub
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] tree-cfg: Allow enum types as result of POINTER_DIFF_EXPR [PR98556]
2021-01-09 9:32 [PATCH] tree-cfg: Allow enum types as result of POINTER_DIFF_EXPR [PR98556] Jakub Jelinek
@ 2021-01-09 9:45 ` Richard Biener
0 siblings, 0 replies; 2+ messages in thread
From: Richard Biener @ 2021-01-09 9:45 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: gcc-patches
On January 9, 2021 10:32:52 AM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>As conversions between signed integers and signed enums with the same
>precision are useless in GIMPLE, it seems strange that we require that
>POINTER_DIFF_EXPR result must be INTEGER_TYPE.
>
>If we really wanted to require that, we'd need to change the gimplifier
>to ensure that, which it isn't the case on the following testcase.
>What is going on during the gimplification is that when we have the
>(enum T) (p - q) cast, it is stripped through
> /* Strip away as many useless type conversions as possible
> at the toplevel. */
> STRIP_USELESS_TYPE_CONVERSION (*expr_p);
>and when the MODIFY_EXPR is gimplified, the *to_p has enum T type,
>while *from_p has intptr_t type and as there is no conversion in
>between,
>we just create GIMPLE_ASSIGN from that.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok also for the branch.
Thanks,
Richard.
>2021-01-08 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/98556
> * tree-cfg.c (verify_gimple_assign_binary): Allow lhs of
> POINTER_DIFF_EXPR to be any integral type.
>
> * c-c++-common/pr98556.c: New test.
>
>--- gcc/tree-cfg.c.jj 2021-01-04 10:25:38.914232907 +0100
>+++ gcc/tree-cfg.c 2021-01-08 15:57:41.605738398 +0100
>@@ -3940,7 +3940,7 @@ verify_gimple_assign_binary (gassign *st
> /* Because we special-case pointers to void we allow difference
> of arbitrary pointers with the same mode. */
> || TYPE_MODE (rhs1_type) != TYPE_MODE (rhs2_type)
>- || TREE_CODE (lhs_type) != INTEGER_TYPE
>+ || !INTEGRAL_TYPE_P (lhs_type)
> || TYPE_UNSIGNED (lhs_type)
> || TYPE_PRECISION (lhs_type) != TYPE_PRECISION (rhs1_type))
> {
>--- gcc/testsuite/c-c++-common/pr98556.c.jj 2021-01-08
>16:03:22.298900002 +0100
>+++ gcc/testsuite/c-c++-common/pr98556.c 2021-01-08 16:03:07.715064312
>+0100
>@@ -0,0 +1,11 @@
>+/* PR c++/98556 */
>+/* { dg-do compile } */
>+/* { dg-options "-O0" } */
>+
>+enum T { E = -__LONG_MAX__ - 1 };
>+
>+enum T
>+foo (char *p, char *q)
>+{
>+ return (enum T) (p - q);
>+}
>
> Jakub
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