[PATCH] Eliminate location wrappers in tree_nop_conversion/STRIP_NOPS

[David Malcolm]

On Tue, 2017-12-19 at 23:03 +0100, Jakub Jelinek wrote:
> On Tue, Dec 19, 2017 at 04:59:34PM -0500, Jason Merrill wrote:
> > > Or do you mean it should strip just the special VIEW_CONVERT_EXPR
> > > that has type identical to the operand's type?
> > 
> > That; interpreting something as the same type seems like a nop.
> 
> Ok, that makes sense.
> 
>       Jakub

Thanks.

How does the following look?

Bootstrap&regrtest in progress; OK for trunk if it passes? (once the rest of
the kit is approved, of course)

gcc/ChangeLog:
        * tree.c (tree_nop_conversion): Return true for location wrapper
        nodes.
        (selftest::check_strip_nops): New function.
        (selftest::test_location_wrappers): Verify that STRIP_NOPS removes
        wrappers.
---
 gcc/tree.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/gcc/tree.c b/gcc/tree.c
index 2d14916..9c9bb77 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -11889,6 +11889,8 @@ tree_nop_conversion (const_tree exp)
 {
   tree outer_type, inner_type;
 
+  if (location_wrapper_p (exp))
+    return true;
   if (!CONVERT_EXPR_P (exp)
       && TREE_CODE (exp) != NON_LVALUE_EXPR)
     return false;
@@ -14208,6 +14210,17 @@ test_vector_cst_patterns ()
   check_vector_cst_fill (elements, build_vector (vector_type, elements), 4);
 }
 
+/* Verify that STRIP_NOPS (NODE) is EXPECTED.
+   Helper function for test_location_wrappers, to deal with STRIP_NOPS
+   modifying its argument in-place.  */
+
+static void
+check_strip_nops (tree node, tree expected)
+{
+  STRIP_NOPS (node);
+  ASSERT_EQ (expected, node);
+}
+
 /* Verify location wrappers.  */
 
 static void
@@ -14242,6 +14255,10 @@ test_location_wrappers ()
   tree r_cast = build1 (NON_LVALUE_EXPR, integer_type_node, int_var);
   ASSERT_FALSE (location_wrapper_p (r_cast));
   ASSERT_EQ (r_cast, tree_strip_any_location_wrapper (r_cast));
+
+  /* Verify that STRIP_NOPS removes wrappers.  */
+  check_strip_nops (wrapped_int_cst, int_cst);
+  check_strip_nops (wrapped_int_var, int_var);
 }
 
 /* Run all of the selftests within this file.  */
-- 
1.8.5.3