On Wed, 29 Mar 2023, Richard Biener wrote:
> The following tells pointer-query to prefer a zero size when we
> are querying for the size range for a write into an object we've
> determined is of zero size. That avoids diagnostics about really
> varying size arguments that just get a meaningful range for example
> because they are multiplied by an element size.
>
> I've adjusted only one call to get_size_range since that's what
> I have a testcase for. I think this is the most sensible
> "workaround" for some of the false positives we see.
>
> Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
>
> OK if it succeeds?
It did, I have now pushed this, it seems like an obvious improvement.
Richard.
> Thanks,
> Richard.
>
> PR tree-optimization/107561
> * gimple-ssa-warn-access.cc (get_size_range): Add flags
> argument and pass it on.
> (check_access): When querying for the size range pass
> SR_ALLOW_ZERO when the known destination size is zero.
>
> * g++.dg/pr71488.C: Remove XFAILed bogus diagnostic again.
> * g++.dg/warn/Warray-bounds-16.C: Likewise.
> ---
> gcc/gimple-ssa-warn-access.cc | 19 +++++++++++++------
> gcc/testsuite/g++.dg/pr71488.C | 1 -
> gcc/testsuite/g++.dg/warn/Warray-bounds-16.C | 1 -
> 3 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
> index 88d44690ade..b3de4b77924 100644
> --- a/gcc/gimple-ssa-warn-access.cc
> +++ b/gcc/gimple-ssa-warn-access.cc
> @@ -1198,10 +1198,10 @@ warn_for_access (location_t loc, tree func, tree
> expr, int opt,
>
> static void
> get_size_range (range_query *query, tree bound, gimple *stmt, tree range[2],
> - const offset_int bndrng[2])
> + int flags, const offset_int bndrng[2])
> {
> if (bound)
> - get_size_range (query, bound, stmt, range);
> + get_size_range (query, bound, stmt, range, flags);
>
> if (!bndrng || (bndrng[0] == 0 && bndrng[1] == HOST_WIDE_INT_M1U))
> return;
> @@ -1347,7 +1347,12 @@ check_access (GimpleOrTree exp, tree dstwrite,
> /* Set RANGE to that of DSTWRITE if non-null, bounded by PAD->DST_BNDRNG
> if valid. */
> gimple *stmt = pad ? pad->stmt : nullptr;
> - get_size_range (rvals, dstwrite, stmt, range, pad ? pad->dst_bndrng :
> NULL);
> + get_size_range (rvals, dstwrite, stmt, range,
> + /* If the destination has known zero size prefer a zero
> + size range to avoid false positives if that's a
> + possibility. */
> + integer_zerop (dstsize) ? SR_ALLOW_ZERO : 0,
> + pad ? pad->dst_bndrng : NULL);
>
> tree func = get_callee_fndecl (exp);
> /* Read vs write access by built-ins can be determined from the const
> @@ -1442,7 +1447,8 @@ check_access (GimpleOrTree exp, tree dstwrite,
> {
> /* Set RANGE to that of MAXREAD, bounded by PAD->SRC_BNDRNG if
> PAD is nonnull and BNDRNG is valid. */
> - get_size_range (rvals, maxread, stmt, range, pad ? pad->src_bndrng :
> NULL);
> + get_size_range (rvals, maxread, stmt, range, 0,
> + pad ? pad->src_bndrng : NULL);
>
> location_t loc = get_location (exp);
> tree size = dstsize;
> @@ -1489,7 +1495,8 @@ check_access (GimpleOrTree exp, tree dstwrite,
> {
> /* Set RANGE to that of MAXREAD, bounded by PAD->SRC_BNDRNG if
> PAD is nonnull and BNDRNG is valid. */
> - get_size_range (rvals, maxread, stmt, range, pad ? pad->src_bndrng :
> NULL);
> + get_size_range (rvals, maxread, stmt, range, 0,
> + pad ? pad->src_bndrng : NULL);
> /* Set OVERREAD for reads starting just past the end of an object. */
> overread = pad->src.sizrng[1] - pad->src.offrng[0] <
> pad->src_bndrng[0];
> range[0] = wide_int_to_tree (sizetype, pad->src_bndrng[0]);
> @@ -2679,7 +2686,7 @@ pass_waccess::check_strncmp (gcall *stmt)
> /* Determine the range of the bound first and bail if it fails; it's
> cheaper than computing the size of the objects. */
> tree bndrng[2] = { NULL_TREE, NULL_TREE };
> - get_size_range (m_ptr_qry.rvals, bound, stmt, bndrng, adata1.src_bndrng);
> + get_size_range (m_ptr_qry.rvals, bound, stmt, bndrng, 0,
> adata1.src_bndrng);
> if (!bndrng[0] || integer_zerop (bndrng[0]))
> return;
>
> diff --git a/gcc/testsuite/g++.dg/pr71488.C b/gcc/testsuite/g++.dg/pr71488.C
> index a89e6465a94..ffe30f1afeb 100644
> --- a/gcc/testsuite/g++.dg/pr71488.C
> +++ b/gcc/testsuite/g++.dg/pr71488.C
> @@ -3,7 +3,6 @@
> // { dg-options "-O3 -std=c++11" }
> // { dg-additional-options "-msse4" { target sse4_runtime } }
> // { dg-require-effective-target c++11 }
> -// { dg-bogus "size 0 overflows" "pr107561" { xfail *-*-* } 0 }
>
> #include <valarray>
>
> diff --git a/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C
> b/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C
> index 49d3437fa1b..89cbadb91c7 100644
> --- a/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C
> +++ b/gcc/testsuite/g++.dg/warn/Warray-bounds-16.C
> @@ -20,7 +20,6 @@ struct S
>
> for (int i = 0; i < m; i++)
> new (p + i) int (); /* { dg-bogus "bounds" "pr102690" { xfail *-*-* }
> } */
> - // { dg-bogus "size 0 overflows" "pr107561" { xfail ilp32 } .-1 }
> }
> };
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
