From: Richard Biener <rguenther@suse.de>
Date: Mon, 25 Jul 2022 15:24:57 +0000 (+0200)
Subject: tree-optimization/106189 - avoid division by zero exception
X-Git-Tag: releases/gcc-12.2.0~68
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5b8458bc35b5df34c1b4b8735975f2686444f6c8;p=thirdparty%2Fgcc.git

tree-optimization/106189 - avoid division by zero exception

The diagnostic code can end up with zero sized array elements
with T[][0] and the wide-int code nicely avoids exceptions when
dividing by zero in one codepath but not in another.  The following
fixes the exception by using wide-int in both paths.

	PR tree-optimization/106189
	* gimple-array-bounds.cc (array_bounds_checker::check_mem_ref):
	Divide using offset_ints.

	* gcc.dg/pr106189.c: New testcase.

(cherry picked from commit bb04f9f23ac0dee2c003118c85372ece50a52220)
---

diff --git a/gcc/gimple-array-bounds.cc b/gcc/gimple-array-bounds.cc
index 7ec8b08c8d29..9e46811a675e 100644
--- a/gcc/gimple-array-bounds.cc
+++ b/gcc/gimple-array-bounds.cc
@@ -534,7 +534,7 @@ array_bounds_checker::check_mem_ref (location_t location, tree ref,
   int i = 0;
   if (aref.offmax[i] < -aref.sizrng[1] || aref.offmax[i = 1] > ubound)
     {
-      HOST_WIDE_INT tmpidx = aref.offmax[i].to_shwi () / eltsize.to_shwi ();
+      HOST_WIDE_INT tmpidx = (aref.offmax[i] / eltsize).to_shwi ();
 
       if (warning_at (location, OPT_Warray_bounds,
 		      "intermediate array offset %wi is outside array bounds "
diff --git a/gcc/testsuite/gcc.dg/pr106189.c b/gcc/testsuite/gcc.dg/pr106189.c
new file mode 100644
index 000000000000..0eca8343c561
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr106189.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Warray-bounds=2 -w" } */
+
+int a_n_0_0_a[][0];
+void a_n_0_0() { T(((char *)a_n_0_0_a)[1]); }