pdp11: Fix handling of common (local and global) vars [PR94134]

As mentioned in the PR, the generic code decides to put the a variable into
lcomm_section, which is a NOSWITCH section and thus the generic code doesn't
switch into a particular section before using
ASM_OUTPUT{_ALIGNED{,_DECL}_}_LOCAL, on many targets that results just in
.lcomm (or for non-local .comm) directives which don't need a switch to some
section, other targets put switch_to_section (bss_section) at the start of
that macro.
pdp11 doesn't do that (and doesn't have bss_section), and so emits the
lcomm/comm variables in whatever section is current (it has only .text/.data
and for DEC assembler rodata).

The following patch fixes that by putting it always into data section, and
additionally avoids emitting an empty line in the assembly for the lcomm
vars.

2020-03-11  Jakub Jelinek  <jakub@redhat.com>

	PR target/94134
	* config/pdp11/pdp11.c (pdp11_asm_output_var): Call switch_to_section
	at the start to switch to data section.  Don't print extra newline if
	.globl directive has not been emitted.

	* gcc.c-torture/execute/pr94134.c: New test.

gcc/ChangeLog

+2020-03-11  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/94134
+	* config/pdp11/pdp11.c (pdp11_asm_output_var): Call switch_to_section
+	at the start to switch to data section.  Don't print extra newline if
+	.globl directive has not been emitted.
+
 2020-03-11  Richard Biener  <rguenther@suse.de>
 
 	* match.pd ((T *)(ptr - ptr-cst) -> &MEM[ptr + -ptr-cst]):

gcc/config/pdp11/pdp11.c

@@ -743,6 +743,7 @@ void
 pdp11_asm_output_var (FILE *file, const char *name, int size,
 		      int align, bool global)
 {
+  switch_to_section (data_section);
   if (align > 8)
     fprintf (file, "\t.even\n");
   if (TARGET_DEC_ASM)
@@ -763,8 +764,8 @@ pdp11_asm_output_var (FILE *file, const char *name, int size,
 	{
 	  fprintf (file, ".globl ");
 	  assemble_name (file, name);
-	}
 	  fprintf (file, "\n");
+	}
       assemble_name (file, name);
       fputs (":", file);
       ASM_OUTPUT_SKIP (file, size);

gcc/testsuite/ChangeLog

+2020-03-11  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/94134
+	* gcc.c-torture/execute/pr94134.c: New test.
+
 2020-03-11  Kito Cheng  <kito.cheng@sifive.com>
 
 	* gcc.target/riscv/interrupt-2.c: Update testcase and expected output.

gcc/testsuite/gcc.c-torture/execute/pr94134.c

+/* PR target/94134 */
+
+static volatile int a = 0;
+static volatile int b = 1;
+
+int
+main ()
+{
+  a++;
+  b++;
+  if (a != 1 || b != 2)
+    __builtin_abort ();
+  return 0;
+}