Hi!
The following is a powerpcspe variant of the sparc PR39645, and rs6000
has the same code (not sure if ever used or dead after powerpcspe removal).
When gimplifying the builtin, because va_arg_tmp.N is not marked as
addressable from the beginning, we call prepare_gimple_addressable which
assigns the previous value (uninitialized in this case) into the now
addressable variable and nothing optimizes it away. Fixed by making it
addressable from the beginning.
Bootstrapped/regtested on {x86_64,i686,powerpc64{,le}}-linux
and tested with a cross to powerpcspe-linux on the testcase, committed as
obvious to trunk.
2018-03-09 Jakub Jelinek <ja...@redhat.com>
PR target/84772
* config/rs6000/rs6000.c (rs6000_gimplify_va_arg): Mark va_arg_tmp
temporary TREE_ADDRESSABLE before gimplification of BUILT_IN_MEMCPY.
* config/powerpcspe/powerpcspe.c (rs6000_gimplify_va_arg): Likewise.
* gcc.dg/pr84772.c: New test.
--- gcc/config/rs6000/rs6000.c.jj 2018-03-07 22:52:01.294479625 +0100
+++ gcc/config/rs6000/rs6000.c 2018-03-09 17:29:09.811949947 +0100
@@ -13537,6 +13537,7 @@ rs6000_gimplify_va_arg (tree valist, tre
tree copy = build_call_expr (builtin_decl_implicit (BUILT_IN_MEMCPY),
3, dest_addr, addr, size_int (rsize * 4));
+ TREE_ADDRESSABLE (tmp) = 1;
gimplify_and_add (copy, pre_p);
addr = dest_addr;
--- gcc/config/powerpcspe/powerpcspe.c.jj 2018-01-03 10:20:14.842537106
+0100
+++ gcc/config/powerpcspe/powerpcspe.c 2018-03-09 17:29:35.291959951 +0100
@@ -14254,6 +14254,7 @@ rs6000_gimplify_va_arg (tree valist, tre
tree copy = build_call_expr (builtin_decl_implicit (BUILT_IN_MEMCPY),
3, dest_addr, addr, size_int (rsize * 4));
+ TREE_ADDRESSABLE (tmp) = 1;
gimplify_and_add (copy, pre_p);
addr = dest_addr;
--- gcc/testsuite/gcc.dg/pr84772.c.jj 2018-03-09 17:34:56.732749975 +0100
+++ gcc/testsuite/gcc.dg/pr84772.c 2018-03-09 17:33:05.095042322 +0100
@@ -0,0 +1,13 @@
+/* PR target/84772 */
+/* { dg-do compile } */
+/* { dg-options "-O -Wuninitialized" } */
+
+#include <stdarg.h>
+
+void
+foo (int *x, int y, va_list ap)
+{
+ __builtin_memset (x, 0, sizeof (int));
+ for (int i = 0; i < y; i++)
+ va_arg (ap, long double); /* { dg-bogus "uninitialized" }
*/
+}
Jakub
