From: Artem Klimov <jakmob...@gmail.com>
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>
---
v2: run the new loop in ipa-visibility only in the whole-program IPA pass;
in decl_default_tls_model, check if any referring function is optimized
when 'optimize == 0' (when running in LTO mode)
Note for reviewers: I noticed there's a place which tries to avoid TLS
promotion, but the comment seems wrong and I could not find a testcase.
I'd suggest we remove it. The compiler can only promote general-dynamic
to local-dynamic and initial-exec to local-exec. The comment refers to
promoting x-dynamic to y-exec, but that cannot happen AFAICT:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=8e1ba78f1b8eedd6c65c6f0e6d6d09a801de5d3d
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..de149e82c 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 (optimize)
+ return true;
+ 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
