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