Hi,
On Tue, Aug 30 2022, Alexander Monakov wrote:
>> I see, thank you for explaining the issue, and sorry if I was a bit stubborn.
>>
>> Does the attached patch (incremental change below) look better? It no longer
>> has the 'shortcut' where iterating over referrers is avoided for the common
>> case of plain 'gcc -O2' and no 'optimize' attributes, but fortunately TLS
>> variables are not so numerous to make chasing that worthwhile.
>
> ... and of course I forgot to add the attachment. Revised patch below.
I hope I am not overstepping my IPA/cgraph maintainer authority here but
I believe the patch is OK for master (assuming it passes bootstrap and
testing).
Thanks,
Martin
>
> ---8<---
>
> From b245015ec465604799aef60b224b1e1e264d4cb8 Mon Sep 17 00:00:00 2001
> From: Artem Klimov <jakmob...@gmail.com>
> Date: Wed, 6 Jul 2022 17:02:01 +0300
> Subject: [PATCH] ipa-visibility: Optimize TLS access [PR99619]
>
> Fix PR99619, which asks to optimize TLS model based on visibility.
> The fix is implemented as an IPA optimization: this allows to take
> optimized visibility status into account (as well as avoid modifying
> all language frontends).
>
> 2022-04-17 Artem Klimov <jakmob...@gmail.com>
>
> gcc/ChangeLog:
>
> * ipa-visibility.cc (function_and_variable_visibility): Promote
> TLS access model afer visibility optimizations.
> * varasm.cc (have_optimized_refs): New helper.
> (optimize_dyn_tls_for_decl_p): New helper. Use it ...
> (decl_default_tls_model): ... here in place of 'optimize' check.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tls/vis-attr-gd.c: New test.
> * gcc.dg/tls/vis-attr-hidden-gd.c: New test.
> * gcc.dg/tls/vis-attr-hidden.c: New test.
> * gcc.dg/tls/vis-flag-hidden-gd.c: New test.
> * gcc.dg/tls/vis-flag-hidden.c: New test.
> * gcc.dg/tls/vis-pragma-hidden-gd.c: New test.
> * gcc.dg/tls/vis-pragma-hidden.c: New test.
>
> Co-Authored-By: Alexander Monakov <amona...@gcc.gnu.org>
> Signed-off-by: Artem Klimov <jakmob...@gmail.com>
> ---
> gcc/ipa-visibility.cc | 19 +++++++++++
> gcc/testsuite/gcc.dg/tls/vis-attr-gd.c | 12 +++++++
> gcc/testsuite/gcc.dg/tls/vis-attr-hidden-gd.c | 13 ++++++++
> gcc/testsuite/gcc.dg/tls/vis-attr-hidden.c | 12 +++++++
> gcc/testsuite/gcc.dg/tls/vis-flag-hidden-gd.c | 13 ++++++++
> gcc/testsuite/gcc.dg/tls/vis-flag-hidden.c | 12 +++++++
> .../gcc.dg/tls/vis-pragma-hidden-gd.c | 17 ++++++++++
> gcc/testsuite/gcc.dg/tls/vis-pragma-hidden.c | 16 ++++++++++
> gcc/varasm.cc | 32 ++++++++++++++++++-
> 9 files changed, 145 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-attr-gd.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-attr-hidden-gd.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-attr-hidden.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-flag-hidden-gd.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-flag-hidden.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-pragma-hidden-gd.c
> create mode 100644 gcc/testsuite/gcc.dg/tls/vis-pragma-hidden.c
>
> diff --git a/gcc/ipa-visibility.cc b/gcc/ipa-visibility.cc
> index 8a27e7bcd..3ed2b7cf6 100644
> --- a/gcc/ipa-visibility.cc
> +++ b/gcc/ipa-visibility.cc
> @@ -873,6 +873,25 @@ function_and_variable_visibility (bool whole_program)
> }
> }
>
> + if (symtab->state >= IPA_SSA)
> + {
> + FOR_EACH_VARIABLE (vnode)
> + {
> + tree decl = vnode->decl;
> +
> + /* Upgrade TLS access model based on optimized visibility status,
> + unless it was specified explicitly or no references remain. */
> + if (DECL_THREAD_LOCAL_P (decl)
> + && !lookup_attribute ("tls_model", DECL_ATTRIBUTES (decl))
> + && vnode->ref_list.referring.length ())
> + {
> + enum tls_model new_model = decl_default_tls_model (decl);
> + gcc_checking_assert (new_model >= decl_tls_model (decl));
> + set_decl_tls_model (decl, new_model);
> + }
> + }
> + }
> +
> if (dump_file)
> {
> fprintf (dump_file, "\nMarking local functions:");
> diff --git a/gcc/varasm.cc b/gcc/varasm.cc
> index 4db8506b1..ffc559431 100644
> --- a/gcc/varasm.cc
> +++ b/gcc/varasm.cc
> @@ -6679,6 +6679,36 @@ init_varasm_once (void)
> #endif
> }
>
> +/* Determine whether SYMBOL is used in any optimized function. */
> +
> +static bool
> +have_optimized_refs (struct symtab_node *symbol)
> +{
> + struct ipa_ref *ref;
> +
> + for (int i = 0; symbol->iterate_referring (i, ref); i++)
> + {
> + cgraph_node *cnode = dyn_cast <cgraph_node *> (ref->referring);
> +
> + if (cnode && opt_for_fn (cnode->decl, optimize))
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/* Check if promoting general-dynamic TLS access model to local-dynamic is
> + desirable for DECL. */
> +
> +static bool
> +optimize_dyn_tls_for_decl_p (const_tree decl)
> +{
> + if (cfun)
> + return optimize;
> + return symtab->state >= IPA && have_optimized_refs (symtab_node::get
> (decl));
> +}
> +
> +
> enum tls_model
> decl_default_tls_model (const_tree decl)
> {
> @@ -6696,7 +6726,7 @@ decl_default_tls_model (const_tree decl)
>
> /* Local dynamic is inefficient when we're not combining the
> parts of the address. */
> - else if (optimize && is_local)
> + else if (is_local && optimize_dyn_tls_for_decl_p (decl))
> kind = TLS_MODEL_LOCAL_DYNAMIC;
> else
> kind = TLS_MODEL_GLOBAL_DYNAMIC;
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-attr-gd.c
> b/gcc/testsuite/gcc.dg/tls/vis-attr-gd.c
> new file mode 100644
> index 000000000..89a248a80
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-attr-gd.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program" } */
> +
> +// tls_model should be global-dynamic due to explicitly specified attribute
> +__attribute__((tls_model("global-dynamic")))
> +__thread int x;
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-global-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-attr-hidden-gd.c
> b/gcc/testsuite/gcc.dg/tls/vis-attr-hidden-gd.c
> new file mode 100644
> index 000000000..e32565588
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-attr-hidden-gd.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program" } */
> +
> +// tls_model should be global-dynamic due to explicitly specified attribute
> +__attribute__((visibility("hidden")))
> +__attribute__((tls_model("global-dynamic")))
> +__thread int x;
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-global-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-attr-hidden.c
> b/gcc/testsuite/gcc.dg/tls/vis-attr-hidden.c
> new file mode 100644
> index 000000000..0d43fc565
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-attr-hidden.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program" } */
> +
> +//tls_model should be local-dynamic due to visibility("hidden")
> +__attribute__((visibility("hidden")))
> +__thread int x;
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-local-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-flag-hidden-gd.c
> b/gcc/testsuite/gcc.dg/tls/vis-flag-hidden-gd.c
> new file mode 100644
> index 000000000..cad41e0c8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-flag-hidden-gd.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program -fvisibility=hidden" } */
> +
> +
> +// tls_model should be global-dynamic due to explicitly specified attribute
> +__attribute__((tls_model("global-dynamic")))
> +__thread int x;
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-global-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-flag-hidden.c
> b/gcc/testsuite/gcc.dg/tls/vis-flag-hidden.c
> new file mode 100644
> index 000000000..a15df092d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-flag-hidden.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program -fvisibility=hidden" } */
> +
> +
> +// tls_model should be local-dynamic due to -fvisibility=hidden
> +__thread int x;
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-local-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden-gd.c
> b/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden-gd.c
> new file mode 100644
> index 000000000..3b3598134
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden-gd.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program" } */
> +
> +
> +#pragma GCC visibility push(hidden)
> +
> +// tls_model should be global-dynamic due to explicitly specified attribute
> +__attribute__((tls_model("global-dynamic")))
> +__thread int x;
> +
> +#pragma GCC visibility pop
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-global-dynamic"
> "whole-program" } } */
> diff --git a/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden.c
> b/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden.c
> new file mode 100644
> index 000000000..1be976442
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tls/vis-pragma-hidden.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fpic } */
> +/* { dg-require-effective-target tls } */
> +/* { dg-options "-O2 -fPIC -fdump-ipa-whole-program" } */
> +
> +
> +#pragma GCC visibility push(hidden)
> +
> +// tls_model should be local-dynamic due to a pragma
> +__thread int x;
> +
> +#pragma GCC visibility pop
> +
> +void reference() { x++; }
> +
> +/* { dg-final { scan-ipa-dump "Varpool flags: tls-local-dynamic"
> "whole-program" } } */
> --
> 2.35.1
