tree-optimization/113630 - invalid code hoisting

The following avoids code hoisting (but also PRE insertion) of
expressions that got value-numbered to another one that are not
a valid replacement (but still compute the same value).  This time
because the access path ends in a structure with different size,
meaning we consider a related access as not trapping because of the
size of the base of the access.

	PR tree-optimization/113630
	* tree-ssa-pre.cc (compute_avail): Avoid registering a
	reference with a representation with not matching base
	access size.

	* gcc.dg/torture/pr113630.c: New testcase.

(cherry picked from commit 724b64304ff5c8ac08a913509afd6fde38d7b767)

diff --git a/gcc/testsuite/gcc.dg/torture/pr113630.c b/gcc/testsuite/gcc.dg/torture/pr113630.c
new file mode 100644 (file)
index 0000000..72ebdef
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr113630.c
@@ -0,0 +1,4 @@
+/* { dg-do run { target { { *-*-linux* *-*-gnu* *-*-uclinux* } && mmap } } } */
+/* { dg-additional-options "-fno-strict-aliasing" } */
+
+#include "pr110799.c"

diff --git a/gcc/tree-ssa-pre.cc b/gcc/tree-ssa-pre.cc
index dfcc9ec4711d2322600f35efddc194dc62beaa10..9e9a2f9d26aaf3864d2b1ad681dd012a153e5033 100644 (file)
--- a/gcc/tree-ssa-pre.cc
+++ b/gcc/tree-ssa-pre.cc
@@ -4224,6 +4224,20 @@ compute_avail (function *fun)
                              = wide_int_to_tree (ptr_type_node,
                                                  wi::to_wide (ref1->op2));
                        }
+                     /* We also need to make sure that the access path
+                        ends in an access of the same size as otherwise
+                        we might assume an access may not trap while in
+                        fact it might.  That's independent of whether
+                        TBAA is in effect.  */
+                     if (TYPE_SIZE (ref1->type) != TYPE_SIZE (ref2->type)
+                         && (! TYPE_SIZE (ref1->type)
+                             || ! TYPE_SIZE (ref2->type)
+                             || ! operand_equal_p (TYPE_SIZE (ref1->type),
+                                                   TYPE_SIZE (ref2->type))))
+                       {
+                         operands.release ();
+                         continue;
+                       }
                      operands.release ();
 
                      result = get_or_alloc_expr_for_reference