compare-elim.c (try_merge_compare): Don't merge compare if address contains a side effect.

2018-06-07  Paul Koning  <ni1d@arrl.net>

gcc/

	* compare-elim.c (try_merge_compare): Don't merge compare if
	address contains a side effect.
	(try_eliminate_compare): Likewise.

gcc/testsuite/

	* gcc.c-torture/compile/20180605-1.c: New test.

From-SVN: r261287

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2018-06-07  Paul Koning  <ni1d@arrl.net>
+
+	* compare-elim.c (try_merge_compare): Don't merge compare if
+	address contains a side effect.
+	(try_eliminate_compare): Likewise.
+
 2018-06-07  Olga Makhotina  <olga.makhotina@intel.com>
 
 	* config.gcc: Support "tremont".

gcc/compare-elim.c

@@ -690,6 +690,13 @@ try_merge_compare (struct comparison *cmp)
     return false;
 
   rtx src = SET_SRC (set);
+
+  /* If the source uses addressing modes with side effects, we can't
+     do the merge because we'd end up with a PARALLEL that has two
+     instances of that side effect in it.  */
+  if (side_effects_p (src))
+    return false;
+
   rtx flags = maybe_select_cc_mode (cmp, src, CONST0_RTX (GET_MODE (src)));
   if (!flags)
     {
@@ -809,6 +816,12 @@ try_eliminate_compare (struct comparison *cmp)
   else
     return false;
 
+  /* If the source uses addressing modes with side effects, we can't
+     do the merge because we'd end up with a PARALLEL that has two
+     instances of that side effect in it.  */
+  if (side_effects_p (cmp_src))
+    return false;
+
   /* Determine if we ought to use a different CC_MODE here.  */
   flags = maybe_select_cc_mode (cmp, cmp_src, in_b);
   if (flags == NULL)

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2018-06-07  Paul Koning  <ni1d@arrl.net>
+
+	* gcc.c-torture/compile/20180605-1.c: New test.
+
 2018-06-07  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/86045

gcc/testsuite/gcc.c-torture/compile/20180605-1.c

@@ -0,0 +1,9 @@
+void f (int *p, int n)
+{
+    int j = 0, k;
+    
+    for (int i = 0; i < n; i++)
+        if ((k = *p++) > 0)
+            j += k;
+    return j;
+}