From: Jason Merrill <jason@redhat.com>
Date: Mon, 11 May 2020 18:05:46 +0000 (-0400)
Subject: c++: Tweak VLA representation.
X-Git-Tag: upstream/12.2.0~16671
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f315d1477d5164cb8ec1a004ce368dd52d47092a;p=platform%2Fupstream%2Fgcc.git

c++: Tweak VLA representation.

If we put the SAVE_EXPR for a VLA size inside the MINUS_EXPR rather than
outside, it will work better with constant folding.

The equivalent change was made in the C front-end in 2004, in commit
r0-64535-g8b0b9aefd29dfe6398857bcf5628662e2f0e21f6

gcc/cp/ChangeLog
2020-05-11  Jason Merrill  <jason@redhat.com>

	* decl.c (compute_array_index_type_loc): Stabilize before building
	the MINUS_EXPR.
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ab5e6ab..9831c25 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,10 @@
 2020-05-11  Jason Merrill  <jason@redhat.com>
 
+	* decl.c (compute_array_index_type_loc): Stabilize before building
+	the MINUS_EXPR.
+
+2020-05-11  Jason Merrill  <jason@redhat.com>
+
 	* decl.c (grokdeclarator): Adjust deprecated_state here.
 	(start_decl): Not here.
 
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index adf9465..dea1ba0 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10449,6 +10449,15 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size,
     itype = build_min (MINUS_EXPR, sizetype, size, integer_one_node);
   else
     {
+      if (!TREE_CONSTANT (size))
+	{
+	  /* A variable sized array.  Arrange for the SAVE_EXPR on the inside
+	     of the MINUS_EXPR, which allows the -1 to get folded with the +1
+	     that happens when building TYPE_SIZE.  */
+	  size = variable_size (size);
+	  stabilize_vla_size (size);
+	}
+
       /* Compute the index of the largest element in the array.  It is
 	 one less than the number of elements in the array.  We save
 	 and restore PROCESSING_TEMPLATE_DECL so that computations in
@@ -10466,11 +10475,6 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size,
 
       if (!TREE_CONSTANT (itype))
 	{
-	  /* A variable sized array.  */
-	  itype = variable_size (itype);
-
-	  stabilize_vla_size (itype);
-
 	  if (sanitize_flags_p (SANITIZE_VLA)
 	      && current_function_decl != NULL_TREE)
 	    {