analyzer: fix qsort issue with array_region keys (PR 93352)

PR analyzer/93352 reports a qsort failure
  "comparator not anti-symmetric: -2147483648, -2147483648)"
within the analyzer on code involving an array access of [0x7fffffff + 1].

The issue is that array_region (which uses int for keys into known
values in the array) uses subtraction to implement int_cmp for sorting
the keys, which isn't going to work for boundary values.

Potentially a wider type should be used, but for now this patch fixes
the ICE by using explicit comparisons rather than subtraction to
implement the qsort callback.

gcc/analyzer/ChangeLog:
	PR analyzer/93352
	* region-model.cc (int_cmp): Rename to...
	(array_region::key_cmp): ...this, using key_t rather than int.
	Rewrite in terms of comparisons rather than subtraction to
	ensure qsort is anti-symmetric when handling extreme values.
	(array_region::walk_for_canonicalization): Update for above
	renaming.
	* region-model.h (array_region::key_cmp): New decl.

gcc/testsuite/ChangeLog:
	PR analyzer/93352
	* gcc.dg/analyzer/pr93352.c: New test.

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/analyzer/region-model.h b/gcc/analyzer/region-model.h
index eea808e..c9c8265 100644
--- a/gcc/analyzer/region-model.h
+++ b/gcc/analyzer/region-model.h
@@ -1319,6 +1319,8 @@ public:
   static key_t key_from_constant (tree cst);
 
  private:
+  static int key_cmp (const void *, const void *);
+
   /* Mapping from tree to child region.  */
   map_t m_map;
 };