From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Wed, 22 Aug 2018 23:43:44 +0000 (+0000)
Subject: tree-ssa-dse.c (compute_trims): Avoid folding away undefined behaviour.
X-Git-Tag: basepoints/gcc-10~4584
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=36d2d101fa9d21189195cce1e90b955096a79779;p=thirdparty%2Fgcc.git

tree-ssa-dse.c (compute_trims): Avoid folding away undefined behaviour.

	* tree-ssa-dse.c (compute_trims): Avoid folding away undefined
	behaviour.

From-SVN: r263793
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 606fb5f6db5a..f362c36962be 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* tree-ssa-dse.c (compute_trims): Avoid folding away undefined
+	behaviour.
+
 2018-08-22  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/87052
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index 4cb8c0f83aca..016aa6cc97c7 100644
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -248,6 +248,13 @@ compute_trims (ao_ref *ref, sbitmap live, int *trim_head, int *trim_tail,
 	 residual handling in mem* and str* functions is usually
 	 reasonably efficient.  */
       *trim_tail = last_orig - last_live;
+
+      /* But don't trim away out of bounds accesses, as this defeats
+	 proper warnings.  */
+      if (*trim_tail
+	  && compare_tree_int (TYPE_SIZE_UNIT (TREE_TYPE (ref->base)),
+			       last_orig) <= 0)
+	*trim_tail = 0;
     }
   else
     *trim_tail = 0;