[PATCH,nvptx] Fix PR85056

[Cesar Philippidis]

As noted in PR85056, the nvptx BE isn't declaring external arrays using
PTX array notation. Specifically, it's emitting code that's missing the
empty angle brackets '[]'. This patch corrects that problem.

Tom, in contrast to my earlier patch in the PR, this patch only
considers external arrays. The patch I posted incorrectly handled
zero-length arrays and empty structs.

I tested this patch with a standalone nvptx toolchain using newlib 3.0,
and I found no new regressions. However I'm still waiting for the
results that are using the older version of newlib. Is this patch OK for
trunk if the results come back clean?

Thanks,
Cesar

2018-03-26  Cesar Philippidis  <ce...@codesourcery.com>

	gcc/

	PR target/85056
	* config/nvptx/nvptx.c (nvptx_assemble_decl_begin): Add '[]' to
	extern array declarations.

	gcc/testsuite/
	* testsuite/gcc.target/nvptx/pr85056.c: New test.
	* testsuite/gcc.target/nvptx/pr85056a.c: New test.


diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index 3cb33ae8c2d..38f25add6ab 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -2038,6 +2038,9 @@ static void
 nvptx_assemble_decl_begin (FILE *file, const char *name, const char *section,
 			   const_tree type, HOST_WIDE_INT size, unsigned align)
 {
+  bool atype = (TREE_CODE (type) == ARRAY_TYPE)
+    && (TYPE_DOMAIN (type) == NULL_TREE);
+
   while (TREE_CODE (type) == ARRAY_TYPE)
     type = TREE_TYPE (type);
 
@@ -2077,6 +2080,8 @@ nvptx_assemble_decl_begin (FILE *file, const char *name, const char *section,
     /* We make everything an array, to simplify any initialization
        emission.  */
     fprintf (file, "[" HOST_WIDE_INT_PRINT_DEC "]", init_frag.remaining);
+  else if (atype)
+    fprintf (file, "[]");
 }
 
 /* Called when the initializer for a decl has been completely output through
diff --git a/gcc/testsuite/gcc.target/nvptx/pr85056.c b/gcc/testsuite/gcc.target/nvptx/pr85056.c
new file mode 100644
index 00000000000..fe7f8af856e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/pr85056.c
@@ -0,0 +1,20 @@
+/* { dg-do run } */
+/* { dg-additional-sources "pr85056a.c" } */
+
+extern void abort ();
+
+extern int a[];
+
+int
+main ()
+{
+  int i, sum;
+
+  for (i = 0; i < 10; i++)
+    sum += a[i];
+
+  if (sum != 55)
+    abort ();
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/nvptx/pr85056a.c b/gcc/testsuite/gcc.target/nvptx/pr85056a.c
new file mode 100644
index 00000000000..a45a5f2b07f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/pr85056a.c
@@ -0,0 +1,3 @@
+/* { dg-skip-if "" { *-*-* } } */
+
+int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };