[gcc r14-8185] gimple-ssa-warn-access: Cast huge params to sizetype before using them in maybe_check_access_sizes [

[Jakub Jelinek]

https://gcc.gnu.org/g:a98a24ac65c1a0ee598e5b54d9e4c921a9744a08

commit r14-8185-ga98a24ac65c1a0ee598e5b54d9e4c921a9744a08
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Jan 17 13:57:07 2024 +0100

    gimple-ssa-warn-access: Cast huge params to sizetype before using them in maybe_check_access_sizes [PR113410]
    
    WHen a VLA is created with some very high precision size expression
    (say __int128, or _BitInt(65535) etc.), we cast it to sizetype, because
    we can't have arrays longer than what can be expressed in sizetype.
    
    But the maybe_check_access_sizes code when trying to determine ranges
    wasn't doing this but was using fixed buffers for the sizes.  While
    __int128 could still be handled (fit into the buffers), obviously
    arbitrary _BitInt parameter ranges can't, they can be in the range of
    up to almost 20KB per number.  It doesn't make sense to print such
    ranges though, no array can be larger than sizetype precision, and
    ranger's range_of_expr can handle NOP_EXPRs/CONVERT_EXPRs wrapping a
    PARM_DECL just fine, so the following patch just casts the excessively
    large counters for the range determination purposes to sizetype.
    
    2024-01-17  Jakub Jelinek  <jakub@redhat.com>
    
            PR middle-end/113410
            * gimple-ssa-warn-access.cc (pass_waccess::maybe_check_access_sizes):
            If access_nelts is integral with larger precision than sizetype,
            fold_convert it to sizetype.
    
            * gcc.dg/bitint-72.c: New test.

Diff:
---
 gcc/gimple-ssa-warn-access.cc    |  9 +++++++++
 gcc/testsuite/gcc.dg/bitint-72.c | 16 ++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index 850aaa0752e..cd083ab2237 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -3406,6 +3406,15 @@ pass_waccess::maybe_check_access_sizes (rdwr_map *rwm, tree fndecl, tree fntype,
       else
 	access_nelts = rwm->get (sizidx)->size;
 
+      /* If access_nelts is e.g. a PARM_DECL with larger precision than
+	 sizetype, such as __int128 or _BitInt(34123) parameters,
+	 cast it to sizetype.  */
+      if (access_nelts
+	  && INTEGRAL_TYPE_P (TREE_TYPE (access_nelts))
+	  && (TYPE_PRECISION (TREE_TYPE (access_nelts))
+	      > TYPE_PRECISION (sizetype)))
+	access_nelts = fold_convert (sizetype, access_nelts);
+
       /* Format the value or range to avoid an explosion of messages.  */
       char sizstr[80];
       tree sizrng[2] = { size_zero_node, build_all_ones_cst (sizetype) };
diff --git a/gcc/testsuite/gcc.dg/bitint-72.c b/gcc/testsuite/gcc.dg/bitint-72.c
new file mode 100644
index 00000000000..a3c44fed355
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bitint-72.c
@@ -0,0 +1,16 @@
+/* PR middle-end/113410 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23" } */
+
+#if __BITINT_MAXWIDTH__ >= 905
+void bar (_BitInt(905) n, int[n]);
+#else
+void bar (int n, int[n]);
+#endif
+
+void
+foo (int n)
+{
+  int buf[n];
+  bar (n, buf);
+}