| Message ID | 20210109093252.GC725145@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | tree-cfg: Allow enum types as result of POINTER_DIFF_EXPR [PR98556] | expand |
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
--- 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); +}
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. Jakub