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author | Jakub Jelinek <jakub@redhat.com> | 2024-06-04 12:28:01 +0200 |
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committer | Jakub Jelinek <jakub@redhat.com> | 2024-06-04 12:28:01 +0200 |
commit | b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c (patch) | |
tree | 1290f91dd0807f18d187dcc78d2a657b694888b6 /gcc/testsuite/gcc.c-torture | |
parent | 09b4ab53155ea16e1fb12c2afcd9b6fe29a31c74 (diff) | |
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builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow and __builtin{add,sub}c [PR108789]
The following testcase is miscompiled, because we use save_expr
on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first
two operands are not INTEGER_CSTs (in that case we just fold it right away)
but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually
create a SAVE_EXPR at all and so we lower it to
*arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \
IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1))
which evaluates the ifn twice and just hope it will be CSEd back.
As *arg2 aliases *arg0, that is not the case.
The builtins are really never const/pure as they store into what
the third arguments points to, so after handling the INTEGER_CST+INTEGER_CST
case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR
by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because
c_fully_fold optimizes it away again, so the following patch marks the
ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the
__builtin_{add,sub,mul}_overflow_p case which were designed for use
especially in constant expressions and don't really evaluate the
realpart side, so we don't really need a SAVE_EXPR in that case).
2024-06-04 Jakub Jelinek <jakub@redhat.com>
PR middle-end/108789
* builtins.cc (fold_builtin_arith_overflow): For ovf_only,
don't call save_expr and don't build REALPART_EXPR, otherwise
set TREE_SIDE_EFFECTS on call before calling save_expr.
(fold_builtin_addc_subc): Set TREE_SIDE_EFFECTS on call before
calling save_expr.
* gcc.c-torture/execute/pr108789.c: New test.
Diffstat (limited to 'gcc/testsuite/gcc.c-torture')
-rw-r--r-- | gcc/testsuite/gcc.c-torture/execute/pr108789.c | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr108789.c b/gcc/testsuite/gcc.c-torture/execute/pr108789.c new file mode 100644 index 0000000..32ee19b --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr108789.c @@ -0,0 +1,39 @@ +/* PR middle-end/108789 */ + +int +add (unsigned *r, const unsigned *a, const unsigned *b) +{ + return __builtin_add_overflow (*a, *b, r); +} + +int +mul (unsigned *r, const unsigned *a, const unsigned *b) +{ + return __builtin_mul_overflow (*a, *b, r); +} + +int +main () +{ + unsigned x; + + /* 1073741824U + 1073741824U should not overflow. */ + x = (__INT_MAX__ + 1U) / 2; + if (add (&x, &x, &x)) + __builtin_abort (); + + /* 256U * 256U should not overflow */ + x = 1U << (sizeof (int) * __CHAR_BIT__ / 4); + if (mul (&x, &x, &x)) + __builtin_abort (); + + /* 2147483648U + 2147483648U should overflow */ + x = __INT_MAX__ + 1U; + if (!add (&x, &x, &x)) + __builtin_abort (); + + /* 65536U * 65536U should overflow */ + x = 1U << (sizeof (int) * __CHAR_BIT__ / 2); + if (!mul (&x, &x, &x)) + __builtin_abort (); +} |