1 From a6219e8e0719b14f474b0dcaa7bde2f4e57474f9 Mon Sep 17 00:00:00 2001
2 From: Jakub Jelinek <jakub@redhat.com>
3 Date: Wed, 17 Nov 2021 13:45:53 +0100
4 Subject: [PATCH] ranger: Fix up fold_using_range::range_of_address [PR103255]
6 If on &base->member the offset isn't constant or isn't zero and
7 -fdelete-null-pointer-checks and not -fwrapv-pointer and base has a range
8 that doesn't include NULL, we return the range of the base.
9 Usually it isn't a big deal, because for most pointers we just use
10 varying, range_zero and range_nonzero ranges and nothing beyond that,
11 but if a pointer is initialized from a constant, we actually track the
12 exact range and in that case this causes miscompilation.
13 As discussed on IRC, I think doing something like:
15 if (off_cst && off.is_constant (&off2))
17 tree cst = wide_int_to_tree (sizetype, off2 / BITS_PER_UNIT);
18 // adjust range r with POINTER_PLUS_EXPR cst
19 if (!range_includes_zero_p (&r))
23 r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
25 could work, given that most of the pointer ranges are just the simple ones
26 perhaps it is too much for little benefit.
28 2021-11-17 Jakub Jelinek <jakub@redhat.com>
30 PR tree-optimization/103255
31 * gimple-range.cc (fold_using_range::range_of_address): Return
32 range_nonzero rather than unadjusted base's range. Formatting fixes.
34 * gcc.c-torture/execute/pr103255.c: New test.
36 (cherry picked from commit c39cb6bf835ca12e590eaa6f90222e51be207c50)
38 gcc/gimple-range.cc | 16 +++++---
39 .../gcc.c-torture/execute/pr103255.c | 41 +++++++++++++++++++
40 2 files changed, 52 insertions(+), 5 deletions(-)
41 create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr103255.c
43 --- a/gcc/gimple-range.cc
44 +++ b/gcc/gimple-range.cc
45 @@ -491,14 +491,20 @@ gimple_ranger::range_of_address (irange
47 /* If &X->a is equal to X, the range of X is the result. */
48 if (off_cst && known_eq (off, 0))
51 else if (flag_delete_null_pointer_checks
52 && !TYPE_OVERFLOW_WRAPS (TREE_TYPE (expr)))
54 - /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
55 - allow going from non-NULL pointer to NULL. */
56 - if(!range_includes_zero_p (&r))
58 + /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
59 + allow going from non-NULL pointer to NULL. */
60 + if (!range_includes_zero_p (&r))
62 + /* We could here instead adjust r by off >> LOG2_BITS_PER_UNIT
63 + using POINTER_PLUS_EXPR if off_cst and just fall back to
65 + r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
69 /* If MEM_REF has a "positive" offset, consider it non-NULL
70 always, for -fdelete-null-pointer-checks also "negative"
72 +++ b/gcc/testsuite/gcc.c-torture/execute/pr103255.c
74 +/* PR tree-optimization/103255 */
83 +#if __SIZEOF_POINTER__ >= 4
84 +#define ADDR 0x400000
97 + for (o = OFF; o <= OFF; o += 0x1000)
100 + u = (struct H *) (ADDR + o);
110 + unsigned *tt = &h->b;
111 + if ((__SIZE_TYPE__) tt != (ADDR + OFF + __builtin_offsetof (struct H, b)))
112 + __builtin_abort ();