Hi Christoph,
The noinit testcase is currently failing on x86_64.
Is the test supposed to be running there?
Thanks,
Tamar
-----Original Message-----
From: gcc-patches-ow...@gcc.gnu.org <gcc-patches-ow...@gcc.gnu.org> On Behalf
Of Christophe Lyon
Sent: Wednesday, August 14, 2019 2:18 PM
To: Christophe Lyon <christophe.l...@linaro.org>; Martin Sebor
<mse...@gmail.com>; gcc Patches <gcc-patches@gcc.gnu.org>; Richard Earnshaw
<richard.earns...@arm.com>; ni...@redhat.com; Jozef Lawrynowicz
<joze...@mittosystems.com>; Richard Sandiford <richard.sandif...@arm.com>
Subject: Re: [PATCH] Add generic support for "noinit" attribute
On Wed, 14 Aug 2019 at 14:14, Richard Sandiford <richard.sandif...@arm.com>
wrote:
>
> Sorry for the slow response, I'd missed that there was an updated patch...
>
> Christophe Lyon <christophe.l...@linaro.org> writes:
> > 2019-07-04 Christophe Lyon <christophe.l...@linaro.org>
> >
> > * lib/target-supports.exp (check_effective_target_noinit): New
> > proc.
> > * gcc.c-torture/execute/noinit-attribute.c: New test.
>
> Second line should be indented by tabs rather than spaces.
>
> > @@ -2224,6 +2234,54 @@ handle_weak_attribute (tree *node, tree name,
> > return NULL_TREE;
> > }
> >
> > +/* Handle a "noinit" attribute; arguments as in struct
> > + attribute_spec.handler. Check whether the attribute is allowed
> > + here and add the attribute to the variable decl tree or otherwise
> > + issue a diagnostic. This function checks NODE is of the expected
> > + type and issues diagnostics otherwise using NAME. If it is not of
> > + the expected type *NO_ADD_ATTRS will be set to true. */
> > +
> > +static tree
> > +handle_noinit_attribute (tree * node,
> > + tree name,
> > + tree args,
> > + int flags ATTRIBUTE_UNUSED,
> > + bool *no_add_attrs)
> > +{
> > + const char *message = NULL;
> > +
> > + gcc_assert (DECL_P (*node));
> > + gcc_assert (args == NULL);
> > +
> > + if (TREE_CODE (*node) != VAR_DECL)
> > + message = G_("%qE attribute only applies to variables");
> > +
> > + /* Check that it's possible for the variable to have a section.
> > + */ else if ((TREE_STATIC (*node) || DECL_EXTERNAL (*node) || in_lto_p)
> > + && DECL_SECTION_NAME (*node))
> > + message = G_("%qE attribute cannot be applied to variables "
> > + "with specific sections");
> > +
> > + if (!targetm.have_switchable_bss_sections)
> > + message = G_("%qE attribute is specific to ELF targets");
>
> Maybe make this an else if too? Or make the VAR_DECL an else if if
> you think the ELF one should win. Either way, it seems odd to have
> the mixture between else if and not.
>
Right, I changed this into an else if.
> > + if (message)
> > + {
> > + warning (OPT_Wattributes, message, name);
> > + *no_add_attrs = true;
> > + }
> > + else
> > + /* If this var is thought to be common, then change this. Common
> > + variables are assigned to sections before the backend has a
> > + chance to process them. Do this only if the attribute is
> > + valid. */
>
> Comment should be indented two spaces more.
>
> > + if (DECL_COMMON (*node))
> > + DECL_COMMON (*node) = 0;
> > +
> > + return NULL_TREE;
> > +}
> > +
> > +
> > /* Handle a "noplt" attribute; arguments as in
> > struct attribute_spec.handler. */
> >
> > diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index
> > f2619e1..f1af1dc 100644
> > --- a/gcc/doc/extend.texi
> > +++ b/gcc/doc/extend.texi
> > @@ -7129,6 +7129,14 @@ The @code{visibility} attribute is described
> > in The @code{weak} attribute is described in @ref{Common Function
> > Attributes}.
> >
> > +@item noinit
> > +@cindex @code{noinit} variable attribute Any data with the
> > +@code{noinit} attribute will not be initialized by the C runtime
> > +startup code, or the program loader. Not initializing data in this
> > +way can reduce program startup times. Specific to ELF targets,
> > +this attribute relies on the linker to place such data in the right
> > +location.
>
> Maybe:
>
> This attribute is specific to ELF targets and relies on the linker to
> place such data in the right location.
>
Thanks, I thought I had chosen a nice turn of phrase :-)
> > diff --git a/gcc/testsuite/gcc.c-torture/execute/noinit-attribute.c
> > b/gcc/testsuite/gcc.c-torture/execute/noinit-attribute.c
> > new file mode 100644
> > index 0000000..ffcf8c6
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.c-torture/execute/noinit-attribute.c
> > @@ -0,0 +1,59 @@
> > +/* { dg-do run } */
> > +/* { dg-require-effective-target noinit */
> > +/* { dg-options "-O2" } */
> > +
> > +/* This test checks that noinit data is handled correctly. */
> > +
> > +extern void _start (void) __attribute__ ((noreturn)); extern void
> > +abort (void) __attribute__ ((noreturn)); extern void exit (int)
> > +__attribute__ ((noreturn));
> > +
> > +int var_common;
> > +int var_zero = 0;
> > +int var_one = 1;
> > +int __attribute__((noinit)) var_noinit; int var_init = 2;
> > +
> > +int __attribute__((noinit)) func(); /* { dg-warning "attribute only
> > +applies to variables" } */ int __attribute__((section
> > +("mysection"), noinit)) var_section1; /* { dg-warning "because it
> > +conflicts with attribute" } */ int __attribute__((noinit, section
> > +("mysection"))) var_section2; /* { dg-warning "because it conflicts
> > +with attribute" } */
> > +
> > +
> > +int
> > +main (void)
> > +{
> > + /* Make sure that the C startup code has correctly initialized
> > +the ordinary variables. */
> > + if (var_common != 0)
> > + abort ();
> > +
> > + /* Initialized variables are not re-initialized during startup, so
> > + check their original values only during the first run of this
> > + test. */
> > + if (var_init == 2)
> > + if (var_zero != 0 || var_one != 1)
> > + abort ();
> > +
> > + switch (var_init)
> > + {
> > + case 2:
> > + /* First time through - change all the values. */
> > + var_common = var_zero = var_one = var_noinit = var_init = 3;
> > + break;
> > +
> > + case 3:
> > + /* Second time through - make sure that d has not been reset. */
> > + if (var_noinit != 3)
> > + abort ();
> > + exit (0);
> > +
> > + default:
> > + /* Any other value for var_init is an error. */
> > + abort ();
> > + }
> > +
> > + /* Simulate a processor reset by calling the C startup code. */
> > + _start ();
> > +
> > + /* Should never reach here. */
> > + abort ();
> > +}
> > diff --git a/gcc/testsuite/lib/target-supports.exp
> > b/gcc/testsuite/lib/target-supports.exp
> > index 815e837..ae05c0a 100644
> > --- a/gcc/testsuite/lib/target-supports.exp
> > +++ b/gcc/testsuite/lib/target-supports.exp
> > @@ -364,6 +364,18 @@ proc check_weak_override_available { } {
> > return [check_weak_available]
> > }
> >
> > +# 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 { } {
> > + if { [istarget arm*-*-eabi]
> > + || [istarget msp430-*-*] } {
> > + return 1
> > + }
> > +
> > + return 0
> > +}
> > +
> > ###############################
> > # proc check_visibility_available { what_kind }
> > ############################### diff --git a/gcc/varasm.c
> > b/gcc/varasm.c index 626a4c9..6ddab0ce 100644
> > --- a/gcc/varasm.c
> > +++ b/gcc/varasm.c
> > @@ -6428,6 +6428,9 @@ default_section_type_flags (tree decl, const char
> > *name, int reloc)
> > || strncmp (name, ".gnu.linkonce.tb.", 17) == 0)
> > flags |= SECTION_TLS | SECTION_BSS;
> >
> > + if (strcmp (name, ".noinit") == 0)
> > + flags |= SECTION_WRITE | SECTION_BSS | SECTION_NOTYPE;
> > +
> > /* Various sections have special ELF types that the assembler will
> > assign by default based on the name. They are neither SHT_PROGBITS
> > nor SHT_NOBITS, so when changing sections we don't want to
> > print a @@ -6748,11 +6751,14 @@ decl_readonly_section (const_tree
> > decl, int reloc)
> >
> > /* Select a section based on the above categorization. */
> >
> > +static section *noinit_section = NULL;
> > +
>
> No longer needed.
Indeed.
>
> OK with those changes, thanks.
Thanks, committed as r274482.
Christophe
> Richard
>
> > section *
> > default_elf_select_section (tree decl, int reloc,
> > unsigned HOST_WIDE_INT align) {
> > const char *sname;
> > +
> > switch (categorize_decl_for_section (decl, reloc))
> > {
> > case SECCAT_TEXT:
> > @@ -6790,6 +6796,13 @@ 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)
> > + {
> > + sname = ".noinit";
> > + break;
> > + }
> > +
> > if (bss_section)
> > return bss_section;
> > sname = ".bss";
