re PR c/84190 (double arithmetic on x86 no longer rounds to nearest)

2018-02-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/84190
	* tree-ssa.c (non_rewritable_mem_ref_base): Do not touch
	volatile accesses if the decl isn't volatile.

	* g++.dg/torture/pr84190.C: New testcase.

From-SVN: r257721

gcc/ChangeLog

+2018-02-16  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/84190
+	* tree-ssa.c (non_rewritable_mem_ref_base): Do not touch
+	volatile accesses if the decl isn't volatile.
+
 2018-02-15  Jason Merrill  <jason@redhat.com>
 
 	PR c++/84314 - ICE with templates and fastcall attribute.

gcc/testsuite/ChangeLog

+2018-02-16  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/84190
+	* g++.dg/torture/pr84190.C: New testcase.
+
 2018-02-15  Martin Sebor  <msebor@redhat.com>
 
 	* gcc.dg/lto/README (dg-lto-warning, dg-lto-message): Document new

gcc/testsuite/g++.dg/torture/pr84190.C

+// { dg-do compile }
+// For slim LTO there's no optimized dump
+// { dg-skip-if "" { *-*-* } { "-flto" } { "" } }
+// { dg-additional-options "-fdump-tree-optimized" }
+
+typedef double T;
+static int equalfn (volatile T* x, volatile T* y);
+T gx, gy;
+int main ()
+{
+  T x = gx, y = gy;
+  return equalfn (&x, &y);
+}
+static int equalfn (volatile T* x, volatile T* y)
+{
+  return (*x == *y);
+}
+
+// There should be exactly two volatile accesses (ignoring clobbers).
+// { dg-final { scan-tree-dump-times " ={v} \[^\{\]" 2 "optimized" } }

gcc/tree-ssa.c

@@ -1427,7 +1427,8 @@ non_rewritable_mem_ref_base (tree ref)
       if (! DECL_P (decl))
 	return NULL_TREE;
       if (! is_gimple_reg_type (TREE_TYPE (base))
-	  || VOID_TYPE_P (TREE_TYPE (base)))
+	  || VOID_TYPE_P (TREE_TYPE (base))
+	  || TREE_THIS_VOLATILE (decl) != TREE_THIS_VOLATILE (base))
 	return decl;
       if ((TREE_CODE (TREE_TYPE (decl)) == VECTOR_TYPE
 	   || TREE_CODE (TREE_TYPE (decl)) == COMPLEX_TYPE)