Hi!
The sanopt maybe_optimize_ubsan_ptr_ifn optimization behaves differently
on 32-bit and on 64-bit targets when using similar arguments maximum or
minimum of ptrdiff_t or values close to it.
The problem is that UHWI is 64-bit, regardless of whether addresses are
64-bit or 32-bit, so for 32-bit targets get_inner_reference returns
NULL offset and all the offset is in pbitpos, while on 64-bit targets
where such large offsets in bytes would fit into shwi, but in bits won't
fit, we return INTEGER_CST offset and often 0 pbitpos.
The following patch handles such offset, so that the sanopt behaves the
same way, and adjusts the testcase (which really should have just 14
matches, the 3 lines with comment changes are already covered by the
overflow check on p = b - SMAX;).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-03-13 Jakub Jelinek <ja...@redhat.com>
PR sanitizer/83392
* sanopt.c (maybe_optimize_ubsan_ptr_ifn): Handle also
INTEGER_CST offset, add it together with bitpos / 8 and
sign extend based on POINTER_SIZE.
* c-c++-common/ubsan/ptr-overflow-sanitization-1.c: Adjust expected
check count from 17 to 14.
--- gcc/sanopt.c.jj 2018-03-02 00:15:54.670780980 +0100
+++ gcc/sanopt.c 2018-03-13 16:54:49.905621373 +0100
@@ -486,12 +486,17 @@ maybe_optimize_ubsan_ptr_ifn (sanopt_ctx
HOST_WIDE_INT bitpos;
base = get_inner_reference (base, &bitsize, &pbitpos, &offset, &mode,
&unsignedp, &reversep, &volatilep);
- if (offset == NULL_TREE
+ if ((offset == NULL_TREE || TREE_CODE (offset) == INTEGER_CST)
&& DECL_P (base)
&& pbitpos.is_constant (&bitpos))
{
gcc_assert (!DECL_REGISTER (base));
- offset_int expr_offset = bitpos / BITS_PER_UNIT;
+ offset_int expr_offset;
+ if (offset)
+ expr_offset = wi::to_offset (offset) + bitpos / BITS_PER_UNIT;
+ else
+ expr_offset = bitpos / BITS_PER_UNIT;
+ expr_offset = wi::sext (expr_offset, POINTER_SIZE);
offset_int total_offset = expr_offset + cur_offset;
if (total_offset != wi::sext (total_offset, POINTER_SIZE))
{
@@ -511,7 +516,7 @@ maybe_optimize_ubsan_ptr_ifn (sanopt_ctx
&& (!is_global_var (base) || decl_binds_to_current_def_p (base)))
{
offset_int base_size = wi::to_offset (DECL_SIZE_UNIT (base));
- if (bitpos >= 0
+ if (!wi::neg_p (expr_offset)
&& wi::les_p (total_offset, base_size))
{
if (!wi::neg_p (total_offset)
@@ -532,7 +537,7 @@ maybe_optimize_ubsan_ptr_ifn (sanopt_ctx
*/
bool sign_cur_offset = !wi::neg_p (cur_offset);
- bool sign_expr_offset = bitpos >= 0;
+ bool sign_expr_offset = !wi::neg_p (expr_offset);
tree base_addr
= build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (base)), base);
--- gcc/testsuite/c-c++-common/ubsan/ptr-overflow-sanitization-1.c.jj
2017-10-11 22:37:52.798901780 +0200
+++ gcc/testsuite/c-c++-common/ubsan/ptr-overflow-sanitization-1.c
2018-03-13 17:00:18.947808006 +0100
@@ -25,9 +25,9 @@ void foo(void)
p2 = p + 2;
p = b - SMAX; /* pointer overflow check is needed */
- p2 = p + (SMAX - 2); /* b - 2: pointer overflow check is needed */
- p2 = p + (SMAX - 1); /* b - 1: pointer overflow check is needed */
- p2 = p + SMAX; /* b: pointer overflow check is needed */
+ p2 = p + (SMAX - 2); /* b - 2: no need to check this */
+ p2 = p + (SMAX - 1); /* b - 1: no need to check this */
+ p2 = p + SMAX; /* b: no need to check this */
p2++; /* b + 1 */
p = c;
@@ -75,4 +75,4 @@ void negative_to_negative (char *ptr)
p2 += 5;
}
-/* { dg-final { scan-tree-dump-times "__ubsan_handle_pointer_overflow" 17
"optimized" } } */
+/* { dg-final { scan-tree-dump-times "__ubsan_handle_pointer_overflow" 14
"optimized" } } */
Jakub
