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- From a6219e8e0719b14f474b0dcaa7bde2f4e57474f9 Mon Sep 17 00:00:00 2001
- From: Jakub Jelinek <jakub@redhat.com>
- Date: Wed, 17 Nov 2021 13:45:53 +0100
- Subject: [PATCH] ranger: Fix up fold_using_range::range_of_address [PR103255]
-
- If on &base->member the offset isn't constant or isn't zero and
- -fdelete-null-pointer-checks and not -fwrapv-pointer and base has a range
- that doesn't include NULL, we return the range of the base.
- Usually it isn't a big deal, because for most pointers we just use
- varying, range_zero and range_nonzero ranges and nothing beyond that,
- but if a pointer is initialized from a constant, we actually track the
- exact range and in that case this causes miscompilation.
- As discussed on IRC, I think doing something like:
- offset_int off2;
- if (off_cst && off.is_constant (&off2))
- {
- tree cst = wide_int_to_tree (sizetype, off2 / BITS_PER_UNIT);
- // adjust range r with POINTER_PLUS_EXPR cst
- if (!range_includes_zero_p (&r))
- return true;
- }
- // Fallback
- r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
- return true;
- could work, given that most of the pointer ranges are just the simple ones
- perhaps it is too much for little benefit.
-
- 2021-11-17 Jakub Jelinek <jakub@redhat.com>
-
- PR tree-optimization/103255
- * gimple-range.cc (fold_using_range::range_of_address): Return
- range_nonzero rather than unadjusted base's range. Formatting fixes.
-
- * gcc.c-torture/execute/pr103255.c: New test.
-
- (cherry picked from commit c39cb6bf835ca12e590eaa6f90222e51be207c50)
- ---
- gcc/gimple-range.cc | 16 +++++---
- .../gcc.c-torture/execute/pr103255.c | 41 +++++++++++++++++++
- 2 files changed, 52 insertions(+), 5 deletions(-)
- create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr103255.c
-
- --- a/gcc/gimple-range.cc
- +++ b/gcc/gimple-range.cc
- @@ -491,14 +491,20 @@ gimple_ranger::range_of_address (irange
- }
- /* If &X->a is equal to X, the range of X is the result. */
- if (off_cst && known_eq (off, 0))
- - return true;
- + return true;
- else if (flag_delete_null_pointer_checks
- && !TYPE_OVERFLOW_WRAPS (TREE_TYPE (expr)))
- {
- - /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
- - allow going from non-NULL pointer to NULL. */
- - if(!range_includes_zero_p (&r))
- - return true;
- + /* For -fdelete-null-pointer-checks -fno-wrapv-pointer we don't
- + allow going from non-NULL pointer to NULL. */
- + if (!range_includes_zero_p (&r))
- + {
- + /* We could here instead adjust r by off >> LOG2_BITS_PER_UNIT
- + using POINTER_PLUS_EXPR if off_cst and just fall back to
- + this. */
- + r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
- + return true;
- + }
- }
- /* If MEM_REF has a "positive" offset, consider it non-NULL
- always, for -fdelete-null-pointer-checks also "negative"
- --- /dev/null
- +++ b/gcc/testsuite/gcc.c-torture/execute/pr103255.c
- @@ -0,0 +1,41 @@
- +/* PR tree-optimization/103255 */
- +
- +struct H
- +{
- + unsigned a;
- + unsigned b;
- + unsigned c;
- +};
- +
- +#if __SIZEOF_POINTER__ >= 4
- +#define ADDR 0x400000
- +#else
- +#define ADDR 0x4000
- +#endif
- +#define OFF 0x20
- +
- +int
- +main ()
- +{
- + struct H *h = 0;
- + unsigned long o;
- + volatile int t = 1;
- +
- + for (o = OFF; o <= OFF; o += 0x1000)
- + {
- + struct H *u;
- + u = (struct H *) (ADDR + o);
- + if (t)
- + {
- + h = u;
- + break;
- + }
- + }
- +
- + if (h == 0)
- + return 0;
- + unsigned *tt = &h->b;
- + if ((__SIZE_TYPE__) tt != (ADDR + OFF + __builtin_offsetof (struct H, b)))
- + __builtin_abort ();
- + return 0;
- +}
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