[PATCH] gimple-ssa-warn-access: Cast huge params to sizetype before using them in maybe_check_access_sizes [PR113410]

[Jakub Jelinek]

Hi!

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.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-01-17  Jakub Jelinek  <ja...@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.

--- gcc/gimple-ssa-warn-access.cc.jj    2024-01-03 11:51:30.087751231 +0100
+++ gcc/gimple-ssa-warn-access.cc       2024-01-16 19:25:35.408958088 +0100
@@ -3406,6 +3406,15 @@ pass_waccess::maybe_check_access_sizes (
       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) };
--- gcc/testsuite/gcc.dg/bitint-72.c.jj 2024-01-16 19:31:33.839938120 +0100
+++ gcc/testsuite/gcc.dg/bitint-72.c    2024-01-16 19:31:06.000328741 +0100
@@ -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);
+}

        Jakub