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

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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.
This commit is contained in:
Jozef Lawrynowicz 2020-11-23 11:43:39 +00:00
parent 4a8c54359a
commit b510765ded
4 changed files with 16 additions and 5 deletions
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2
gcc/testsuite/gcc.c-torture/execute/noinit-attribute.c
View File

@ -1,6 +1,6 @@
/* { dg-do run } */
/* { dg-require-effective-target noinit } */
/* { dg-options "-O2" } */
/* { dg-options "-Wattributes" } */
/* { dg-skip-if "data LMA != VMA" { msp430-*-* } { "-mlarge" } } */
/* This test checks that noinit data is handled correctly.

2
gcc/testsuite/lib/target-supports.exp
View File

@ -368,7 +368,7 @@ proc check_weak_override_available { } {
return [check_weak_available]
}
# The noinit attribute is only supported by some targets.
# The "noinit" attribute is only supported by some targets.
# This proc returns 1 if it's supported, 0 if it's not.
proc check_effective_target_noinit { } {

7
gcc/tree.h
View File

@ -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

10
gcc/varasm.c
View File

@ -1241,6 +1241,7 @@ get_variable_section (tree decl, bool prefer_noswitch_p)
if (ADDR_SPACE_GENERIC_P (as)
&& !DECL_THREAD_LOCAL_P (decl)
&& !DECL_NOINIT_P (decl)
&& !(prefer_noswitch_p && targetm.have_switchable_bss_sections)
&& bss_initializer_p (decl))
{
@ -7042,13 +7043,11 @@ default_elf_select_section (tree decl, int reloc,
sname = ".tdata";
break;
case SECCAT_BSS:
if (DECL_P (decl)
&& lookup_attribute ("noinit", DECL_ATTRIBUTES (decl)) != NULL_TREE)
if (DECL_P (decl) && DECL_NOINIT_P (decl))
{
sname = ".noinit";
break;
}
if (bss_section)
return bss_section;
sname = ".bss";
@ -7111,6 +7110,11 @@ default_unique_section (tree decl, int reloc)
prefix = one_only ? ".s" : ".sdata";
break;
case SECCAT_BSS:
if (DECL_P (decl) && DECL_NOINIT_P (decl))
{
prefix = one_only ? ".n" : ".noinit";
break;
}
prefix = one_only ? ".b" : ".bss";
break;
case SECCAT_SBSS: