Fix "noinit" attribute being ignored for -O0 and -fdata-sections

Variables with the "noinit" attribute are ignored at -O0 because they
are treated like a regular bss variable and placed in the .bss section.

With -fdata-sections they are ignored because they are not handled in
resolve_unique_section.

gcc/ChangeLog:

	* tree.h (DECL_NOINIT_P): Define.
	* varasm.c (DECL_NOINIT_P): Check DECL_NOINIT_P before using
	unnamed bss/lcomm sections for bss_initializer variables.
	(default_elf_select_section): Use DECL_NOINIT_P instead of
	looking up attribute for .noinit section selection.
	(default_unique_section): Check DECL_NOINIT_P for .noinit
	section selection.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/execute/noinit-attribute.c: Don't override
	optimization options set by torture test harness.
	* lib/target-supports.exp (check_effective_target_noinit): Adjust
	comment formatting.

1 files changed, 7 insertions, 0 deletions

diff --git a/gcc/tree.h b/gcc/tree.h
index 20f66a0..664449a 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -2662,6 +2662,13 @@ extern tree vector_element_bits_tree (const_tree);
 #define DECL_PRESERVE_P(DECL) \
   DECL_COMMON_CHECK (DECL)->decl_common.preserve_flag
 
+/* Nonzero for a decl that is decorated with the "noinit" attribute.
+   decls with this attribute are placed into the ".noinit" section, so they are
+   not initialized by the target's startup code.  */
+#define DECL_NOINIT_P(DECL)	\
+  (DECL_P (DECL)		\
+   && (lookup_attribute ("noinit", DECL_ATTRIBUTES (DECL)) != NULL_TREE))
+
 /* For function local variables of COMPLEX and VECTOR types,
    indicates that the variable is not aliased, and that all
    modifications to the variable have been adjusted so that