On Wed, 14 Aug 2019 at 17:59, Tamar Christina <tamar.christ...@arm.com> wrote:
>
> Hi Christoph,
>
> The noinit testcase is currently failing on x86_64.
>
> Is the test supposed to be running there?
>
No, there's an effective-target to skip it.
But I notice a typo:
+/* { dg-require-effective-target noinit */
(missing closing brace)
Could it explain why it's failing on x86_64 ?
> 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";
