[gcc/devel/ranger] Do not put incomplete CONSTRUCTORs into static memory

[Aldy Hernandez]

https://gcc.gnu.org/g:2badc9885330b56dfabb49328c42de792bc67b1e

commit 2badc9885330b56dfabb49328c42de792bc67b1e
Author: Eric Botcazou <ebotcazou@gcc.gnu.org>
Date:   Tue May 5 12:31:26 2020 +0200

    Do not put incomplete CONSTRUCTORs into static memory
    
    The CONSTRUCTOR_NO_CLEARING flag was invented to avoid generating a memset
    for  CONSTRUCTORS that lack elements, but it turns out that the gimplifier
    can generate a memcpy for them instead, which is worse performance-wise,
    so this prevents it from doing that for them.
    
            * gimplify.c (gimplify_init_constructor): Do not put the constructor
            into static memory if it is not complete.

Diff:
---
 gcc/ChangeLog                    |  5 +++++
 gcc/gimplify.c                   |  2 +-
 gcc/testsuite/ChangeLog          |  4 ++++
 gcc/testsuite/gnat.dg/aggr29.adb | 12 ++++++++++++
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2267a63bca1..73634780e0f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-05  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gimplify.c (gimplify_init_constructor): Do not put the constructor
+	into static memory if it is not complete.
+
 2020-05-05  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/94949
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 2f2c51b2d89..7807e30fb2e 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -4995,8 +4995,8 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	   all-zero initializers (which aren't big enough to merit
 	   clearing), and don't try to make bitwise copies of
 	   TREE_ADDRESSABLE types.  */
-
 	if (valid_const_initializer
+	    && complete_p
 	    && !(cleared || num_nonzero_elements == 0)
 	    && !TREE_ADDRESSABLE (type))
 	  {
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2ffa0f8f434..7f973949a7f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-05  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/aggr29.adb: New test.
+
 2020-05-05  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/94949
diff --git a/gcc/testsuite/gnat.dg/aggr29.adb b/gcc/testsuite/gnat.dg/aggr29.adb
new file mode 100644
index 00000000000..c82a6f4c768
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/aggr29.adb
@@ -0,0 +1,12 @@
+-- { dg-do compile }
+-- { dg-options "-fdump-tree-gimple" }
+
+with Ada.Streams; use Ada.Streams;
+
+procedure Aggr29 is
+  A : aliased Stream_Element_Array := (1 .. 512 => <>);
+begin
+  null;
+end;
+
+-- { dg-final { scan-tree-dump-not "a___UNC = \\*" "gimple" } }