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[PATCH] Add __attribute((tls_model("initial-exec")))
- From: Jakub Jelinek <jakub at redhat dot com>
- To: rth at redhat dot com, roland at redhat dot com, drepper at redhat dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Wed, 11 Sep 2002 16:20:03 +0200
- Subject: [PATCH] Add __attribute((tls_model("initial-exec")))
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
ATM the TLS model is determined on a per-file basis and is basically
centered around who references the TLS variables, not who provides them.
E.g. suppose glibc exports errno as STT_TLS symbol. For libc.so we can
assume the variable will resolve into the initial TLS block, so although
random shared library using TLS needs to be compiled with global-dynamic
model so that it can be dlopened, references to errno can be using
initial-exec model and resolved once at dlopen time, not every time
they are referenced.
Similarly, if a dynamically linked program references errno, unless
we go for TLS COPY relocs which IMHO we don't want and is compiled with
-ftls-model=local-exec, it will not link, since local-exec model cannot
reference variables outside of the binary.
With the patch below, glibc can declare errno as:
extern __thread int errno __attribute__ ((tls_model ("initial-exec")));
and optimize -ftls-model={global,local}-dynamic libs and
make -ftls-model=local-exec binaries work at the same time.
2002-09-11 Jakub Jelinek <jakub@redhat.com>
* doc/extend.texi (tls_model): Document.
* varasm.c (decl_tls_model): New.
* c-common.c (handle_tls_model_attribute): New.
(c_common_attribute_table): Add tls_model.
* config/alpha/alpha.c (alpha_encode_section_info): Use
decl_tls_model.
* flags.h (enum tls_model, flag_tls_default): Move...
* tree.h (enum tls_model, flag_tls_default): ...here.
(decl_tls_model): New prototype.
* config/ia64/ia64.c (ia64_encode_section_info): Likewise.
* config/i386/i386.c (ix86_encode_section_info): Likewise.
* config/i386/i386.md (tls_global_dynamic, tls_local_dynamic_base):
Allow !flag_pic.
--- gcc/doc/extend.texi.jj 2002-09-10 13:47:53.000000000 +0200
+++ gcc/doc/extend.texi 2002-09-11 15:50:09.000000000 +0200
@@ -2332,6 +2332,15 @@ since it is known that the calling funct
Not all ELF targets support this attribute.
+@item tls_model ("@var{tls_model}")
+@cindex @code{tls_model} attribute
+The @code{tls_model} attribute sets thread-local storage model
+(@pxref{Thread-Local}) of a particular @code{__thread} variable,
+overriding @code{-ftls-model=} command line switch on a per-variable
+basis.
+The @var{tls_model} argument should be one of @code{global-dynamic},
+@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
+
@item regparm (@var{number})
@cindex functions that are passed arguments in registers on the 386
On the Intel 386, the @code{regparm} attribute causes the compiler to
--- gcc/config/alpha/alpha.c.jj 2002-08-28 21:13:12.000000000 +0200
+++ gcc/config/alpha/alpha.c 2002-09-11 14:33:12.000000000 +0200
@@ -1872,22 +1872,7 @@ alpha_encode_section_info (decl, first)
/* Care for TLS variables. */
if (TREE_CODE (decl) == VAR_DECL && DECL_THREAD_LOCAL (decl))
{
- enum tls_model kind;
- if (!flag_pic)
- {
- if (is_local)
- kind = TLS_MODEL_LOCAL_EXEC;
- else
- kind = TLS_MODEL_INITIAL_EXEC;
- }
- else if (is_local)
- kind = TLS_MODEL_LOCAL_DYNAMIC;
- else
- kind = TLS_MODEL_GLOBAL_DYNAMIC;
- if (kind < flag_tls_default)
- kind = flag_tls_default;
-
- switch (kind)
+ switch (decl_tls_model (decl))
{
case TLS_MODEL_GLOBAL_DYNAMIC:
encoding = 'G';
--- gcc/config/i386/i386.c.jj 2002-09-10 14:40:49.000000000 +0200
+++ gcc/config/i386/i386.c 2002-09-11 14:37:48.000000000 +0200
@@ -5493,23 +5493,7 @@ ix86_encode_section_info (decl, first)
const char *symbol_str;
char *newstr;
size_t len;
- enum tls_model kind;
-
- if (!flag_pic)
- {
- if (local_p)
- kind = TLS_MODEL_LOCAL_EXEC;
- else
- kind = TLS_MODEL_INITIAL_EXEC;
- }
- /* Local dynamic is inefficient when we're not combining the
- parts of the address. */
- else if (optimize && local_p)
- kind = TLS_MODEL_LOCAL_DYNAMIC;
- else
- kind = TLS_MODEL_GLOBAL_DYNAMIC;
- if (kind < flag_tls_default)
- kind = flag_tls_default;
+ enum tls_model kind = decl_tls_model (decl);
symbol_str = XSTR (symbol, 0);
--- gcc/config/i386/i386.md.jj 2002-09-10 13:47:40.000000000 +0200
+++ gcc/config/i386/i386.md 2002-09-11 16:01:38.000000000 +0200
@@ -13824,9 +13824,13 @@
(clobber (reg:CC 17))])]
""
{
- if (!flag_pic)
- abort ();
- operands[2] = pic_offset_table_rtx;
+ if (flag_pic)
+ operands[2] = pic_offset_table_rtx;
+ else
+ {
+ operands[2] = gen_reg_rtx (Pmode);
+ emit_insn (gen_set_got (operands[2]));
+ }
operands[3] = ix86_tls_get_addr ();
})
@@ -13866,8 +13870,13 @@
(clobber (reg:CC 17))])]
""
{
- if (!flag_pic)
- abort ();
+ if (flag_pic)
+ operands[2] = pic_offset_table_rtx;
+ else
+ {
+ operands[2] = gen_reg_rtx (Pmode);
+ emit_insn (gen_set_got (operands[2]));
+ }
operands[1] = pic_offset_table_rtx;
operands[2] = ix86_tls_get_addr ();
})
--- gcc/config/ia64/ia64.c.jj 2002-09-10 13:47:41.000000000 +0200
+++ gcc/config/ia64/ia64.c 2002-09-11 14:32:13.000000000 +0200
@@ -7134,24 +7134,7 @@ ia64_encode_section_info (decl, first)
is_local = (*targetm.binds_local_p) (decl);
if (TREE_CODE (decl) == VAR_DECL && DECL_THREAD_LOCAL (decl))
- {
- enum tls_model kind;
- if (!flag_pic)
- {
- if (is_local)
- kind = TLS_MODEL_LOCAL_EXEC;
- else
- kind = TLS_MODEL_INITIAL_EXEC;
- }
- else if (is_local)
- kind = TLS_MODEL_LOCAL_DYNAMIC;
- else
- kind = TLS_MODEL_GLOBAL_DYNAMIC;
- if (kind < flag_tls_default)
- kind = flag_tls_default;
-
- encoding = " GLil"[kind];
- }
+ encoding = " GLil"[decl_tls_model (decl)];
/* Determine if DECL will wind up in .sdata/.sbss. */
else if (is_local && ia64_in_small_data_p (decl))
encoding = 's';
--- gcc/varasm.c.jj 2002-09-10 13:47:31.000000000 +0200
+++ gcc/varasm.c 2002-09-11 15:30:31.000000000 +0200
@@ -4680,6 +4680,52 @@ init_varasm_once ()
const_alias_set = new_alias_set ();
}
+enum tls_model
+decl_tls_model (decl)
+ tree decl;
+{
+ enum tls_model kind;
+ tree attr = lookup_attribute ("tls_model", DECL_ATTRIBUTES (decl));
+ bool is_local;
+
+ if (attr)
+ {
+ attr = TREE_VALUE (TREE_VALUE (attr));
+ if (TREE_CODE (attr) != STRING_CST)
+ abort ();
+ if (!strcmp (TREE_STRING_POINTER (attr), "local-exec"))
+ kind = TLS_MODEL_LOCAL_EXEC;
+ else if (!strcmp (TREE_STRING_POINTER (attr), "initial-exec"))
+ kind = TLS_MODEL_INITIAL_EXEC;
+ else if (!strcmp (TREE_STRING_POINTER (attr), "local-dynamic"))
+ kind = optimize ? TLS_MODEL_LOCAL_DYNAMIC : TLS_MODEL_GLOBAL_DYNAMIC;
+ else if (!strcmp (TREE_STRING_POINTER (attr), "global-dynamic"))
+ kind = TLS_MODEL_GLOBAL_DYNAMIC;
+ else
+ abort ();
+ return kind;
+ }
+
+ is_local = (*targetm.binds_local_p) (decl);
+ if (!flag_pic)
+ {
+ if (is_local)
+ kind = TLS_MODEL_LOCAL_EXEC;
+ else
+ kind = TLS_MODEL_INITIAL_EXEC;
+ }
+ /* Local dynamic is inefficient when we're not combining the
+ parts of the address. */
+ else if (optimize && is_local)
+ kind = TLS_MODEL_LOCAL_DYNAMIC;
+ else
+ kind = TLS_MODEL_GLOBAL_DYNAMIC;
+ if (kind < flag_tls_default)
+ kind = flag_tls_default;
+
+ return kind;
+}
+
/* Select a set of attributes for section NAME based on the properties
of DECL and whether or not RELOC indicates that DECL's initializer
might contain runtime relocations.
--- gcc/c-common.c.jj 2002-09-10 13:47:22.000000000 +0200
+++ gcc/c-common.c 2002-09-11 13:39:58.000000000 +0200
@@ -734,6 +734,8 @@ static tree handle_alias_attribute PARAM
bool *));
static tree handle_visibility_attribute PARAMS ((tree *, tree, tree, int,
bool *));
+static tree handle_tls_model_attribute PARAMS ((tree *, tree, tree, int,
+ bool *));
static tree handle_no_instrument_function_attribute PARAMS ((tree *, tree,
tree, int,
bool *));
@@ -833,6 +835,8 @@ const struct attribute_spec c_common_att
handle_vector_size_attribute },
{ "visibility", 1, 1, true, false, false,
handle_visibility_attribute },
+ { "tls_model", 1, 1, true, false, false,
+ handle_tls_model_attribute },
{ "nonnull", 0, -1, false, true, true,
handle_nonnull_attribute },
{ "nothrow", 0, 0, true, false, false,
@@ -6087,6 +6091,49 @@ handle_visibility_attribute (node, name,
return NULL_TREE;
}
+/* Handle an "tls_model" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_tls_model_attribute (node, name, args, flags, no_add_attrs)
+ tree *node;
+ tree name;
+ tree args;
+ int flags ATTRIBUTE_UNUSED;
+ bool *no_add_attrs;
+{
+ tree decl = *node;
+
+ if (! DECL_THREAD_LOCAL (decl))
+ {
+ warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
+ *no_add_attrs = true;
+ }
+ else
+ {
+ tree id;
+
+ id = TREE_VALUE (args);
+ if (TREE_CODE (id) != STRING_CST)
+ {
+ error ("tls_model arg not a string");
+ *no_add_attrs = true;
+ return NULL_TREE;
+ }
+ if (strcmp (TREE_STRING_POINTER (id), "local-exec")
+ && strcmp (TREE_STRING_POINTER (id), "initial-exec")
+ && strcmp (TREE_STRING_POINTER (id), "local-dynamic")
+ && strcmp (TREE_STRING_POINTER (id), "global-dynamic"))
+ {
+ error ("tls_model arg must be one of \"local-exec\", \"initial-exec\", \"local-dynamic\" or \"global-dynamic\"");
+ *no_add_attrs = true;
+ return NULL_TREE;
+ }
+ }
+
+ return NULL_TREE;
+}
+
/* Handle a "no_instrument_function" attribute; arguments as in
struct attribute_spec.handler. */
--- gcc/tree.h.jj 2002-08-19 13:25:17.000000000 +0200
+++ gcc/tree.h 2002-09-11 15:27:17.000000000 +0200
@@ -2098,7 +2098,17 @@ extern GTY(()) tree integer_types[itk_no
#define long_unsigned_type_node integer_types[itk_unsigned_long]
#define long_long_integer_type_node integer_types[itk_long_long]
#define long_long_unsigned_type_node integer_types[itk_unsigned_long_long]
+
+/* Set to the default thread-local storage (tls) model to use. */
+
+enum tls_model {
+ TLS_MODEL_GLOBAL_DYNAMIC = 1,
+ TLS_MODEL_LOCAL_DYNAMIC,
+ TLS_MODEL_INITIAL_EXEC,
+ TLS_MODEL_LOCAL_EXEC
+};
+extern enum tls_model flag_tls_default;
#define NULL_TREE (tree) NULL
@@ -2982,6 +2992,7 @@ extern void make_decl_rtl PARAMS ((tree
extern void make_decl_one_only PARAMS ((tree));
extern int supports_one_only PARAMS ((void));
extern void variable_section PARAMS ((tree, int));
+enum tls_model decl_tls_model PARAMS ((tree));
/* In fold-const.c */
extern int div_and_round_double PARAMS ((enum tree_code, int,
--- gcc/flags.h.jj 2002-08-03 01:21:54.000000000 +0200
+++ gcc/flags.h 2002-09-11 15:26:20.000000000 +0200
@@ -467,17 +467,6 @@ extern int flag_pedantic_errors;
extern int flag_pic;
-/* Set to the default thread-local storage (tls) model to use. */
-
-enum tls_model {
- TLS_MODEL_GLOBAL_DYNAMIC = 1,
- TLS_MODEL_LOCAL_DYNAMIC,
- TLS_MODEL_INITIAL_EXEC,
- TLS_MODEL_LOCAL_EXEC
-};
-
-extern enum tls_model flag_tls_default;
-
/* Nonzero means generate extra code for exception handling and enable
exception handling. */
Jakub