Hi!
When users don't use constexpr everywhere in initialization of namespace
scope non-comdat vars and the initializers aren't constant when FE is
looking at them, the FE performs dynamic initialization of those variables.
But after inlining and some constant propagation, we often end up with
just storing constants into those variables in the _GLOBAL__sub_I_*
constructor.
C++ gives us permission to change some of that dynamic initialization
back into static initialization - https://eel.is/c++draft/basic.start.static#3
For classes that need (dynamic) construction, I believe access to some var
from other dynamic construction before that var is constructed is UB, but
as the example in the above mentioned spot of C++:
inline double fd() { return 1.0; }
extern double d1;
double d2 = d1; // unspecified:
// either statically initialized to 0.0 or
// dynamically initialized to 0.0 if d1 is
// dynamically initialized, or 1.0 otherwise
double d1 = fd(); // either initialized statically or dynamically to 1.0
some vars can be used before they are dynamically initialized and the
implementation can still optimize those into static initialization.
The following patch attempts to optimize some such cases back into
DECL_INITIAL initializers and where possible (originally const vars without
mutable members) put those vars back to .rodata etc.
Because we put all dynamic initialization from a single TU into one single
function (well, originally one function per priority but typically inline
those back into one function), we can either have a simpler approach
(from the PR it seems that is what LLVM uses) where either we manage to
optimize all dynamic initializers into constant in the TU, or nothing,
or by adding some markup - in the form of a pair of internal functions in
this patch - around each dynamic initialization that can be optimized,
we can optimize each dynamic initialization separately.
The patch adds a new pass that is invoked (through gate check) only on
DECL_ARTIFICIAL DECL_STATIC_CONSTRUCTOR functions, and looks there for
sequences like:
.DYNAMIC_INIT_START (&b, 0);
b = 1;
.DYNAMIC_INIT_END (&b);
or
.DYNAMIC_INIT_START (&e, 1);
# DEBUG this => &e.f
MEM[(struct S *)&e + 4B] ={v} {CLOBBER};
MEM[(struct S *)&e + 4B].a = 1;
MEM[(struct S *)&e + 4B].b = 2;
MEM[(struct S *)&e + 4B].c = 3;
# DEBUG BEGIN_STMT
MEM[(struct S *)&e + 4B].d = 6;
# DEBUG this => NULL
.DYNAMIC_INIT_END (&e);
(where between the pair of markers everything is either debug stmts or
stores of constants into the variables or their parts).
The pass needs to be done late enough so that after IPA all the needed
constant propagation and perhaps loop unrolling is done, on the other
side should be early enough so that if we can't optimize it, we can
remove those .DYNAMIC_INIT* internal calls that could prevent some
further optimizations (they have fnspec such that they pretend to read
the corresponding variable).
Currently the optimization is only able to optimize cases where the whole
variable is stored in a single store (typically scalar variables), or
uses the native_{encode,interpret}* infrastructure to create or update
the CONSTRUCTOR. This means that except for the first category, we can't
right now handle unions or anything that needs relocations (vars containing
pointers to other vars or references).
I think it would be nice to incrementally add before the native_* fallback
some attempt to just create or update a CONSTRUCTOR if possible. If we only
see var.a.b.c.d[10].e = const; style of stores, this shouldn't be that hard
as the whole access path is recorded there and we'd just need to decide what
to do with unions if two or more union members are accessed. And do a deep
copy of the CONSTRUCTOR and try to efficiently update the copy afterwards
(the CONSTRUCTORs should be sorted on increasing offsets of the
members/elements, so doing an ordered vec insertion might not be the best
idea). But MEM_REFs complicate this, parts or all of the access path
is lost. For non-unions in most cases we could try to guess which field
it is (do we have some existing function to do that? I vaguely remember
we've been doing that in some cases in the past in some folding but stopped
doing so) but with unions it will be harder or impossible.
As the middle-end can't easily differentiate between const variables without
and with mutable members, both of those will have TREE_READONLY on the
var decl clear (because of dynamic initialization) and TYPE_READONLY set
on the type, the patch remembers this in an extra argument to
.DYNAMIC_INIT_START (true if it is ok to set TREE_READONLY on the var decl
back if the var dynamic initialization could be optimized into DECL_INITIAL).
Thinking more about it, I'm not sure about const vars without mutable
members with non-trivial destructors, do we register their dtors dynamically
through __cxa_atexit in the ctors (that would mean the optimization
currently punts on them), or not (in that case we could put it into .rodata
even when the dtor will want to perhaps write to them)?
Anyway, forgot to do another set of bootstraps with gathering statistics how
many vars were optimized, so just trying to figure it out from the sizes of
_GLOBAL__sub_I_* functions:
# Without patch, x86_64-linux cc1plus
$ readelf -Ws obj50/gcc/cc1plus | grep ' _GLOBAL__sub_I_' | awk
'BEGIN{I=0}{I=I+$3}END{print I}'
13934
# With the patch, x86_64-linux cc1plus
$ readelf -Ws obj52/gcc/cc1plus | grep ' _GLOBAL__sub_I_' | awk
'BEGIN{I=0}{I=I+$3}END{print I}'
6966
# Without patch, i686-linux cc1plus
$ readelf -Ws obj51/gcc/cc1plus | grep ' _GLOBAL__sub_I_' | awk
'BEGIN{I=0}{I=I+$3}END{print I}'
24158
# With the patch, i686-linux cc1plus
$ readelf -Ws obj53/gcc/cc1plus | grep ' _GLOBAL__sub_I_' | awk
'BEGIN{I=0}{I=I+$3}END{print I}'
10536
That seems like a huge improvement, although on a closer look, most of that
saving is from just one TU:
$ readelf -Ws obj50/gcc/i386-options.o | grep ' _GLOBAL__sub_I_' | awk '{print
$3}'
6693
$ readelf -Ws obj52/gcc/i386-options.o | grep ' _GLOBAL__sub_I_' | awk '{print
$3}'
1
$ readelf -Ws obj51/gcc/i386-options.o | grep ' _GLOBAL__sub_I_' | awk '{print
$3}'
13001
$ readelf -Ws obj53/gcc/i386-options.o | grep ' _GLOBAL__sub_I_' | awk '{print
$3}'
1
So, the shrinking on all the dynamic initialization functions except
i386-options.o is:
7241 -> 6965 for 64-bit and
11157 -> 10535 for 32-bit.
Will try to use constexpr for i386-options.c later today.
Another optimization that could be useful but not sure if it can be easily
done is if we before expansion of the _GLOBAL__sub_I_* functions end up with
nothing in their body (that's those 1 byte functions on x86) perhaps either
not emit those functions at all or at least don't register them in
.init_array etc. so that cycles aren't wasted at runtime:
$ readelf -Ws obj50/gcc/{*,*/*}.o | grep ' _GLOBAL__sub_I_' | awk '($3 ==
1){print $3}' | wc -l
4
$ readelf -Ws obj52/gcc/{*,*/*}.o | grep ' _GLOBAL__sub_I_' | awk '($3 ==
1){print $3}' | wc -l
87
$ readelf -Ws obj51/gcc/{*,*/*}.o | grep ' _GLOBAL__sub_I_' | awk '($3 ==
1){print $3}' | wc -l
4
$ readelf -Ws obj53/gcc/{*,*/*}.o | grep ' _GLOBAL__sub_I_' | awk '($3 ==
1){print $3}' | wc -l
84
Also, wonder if I should add some new -f* option to control the optimization
or doing it always at -O+ with -fdisable-tree-pass-dyninit as a way to
disable it is good enough, and whether the 1024 hardcoded constant
(upper bound on optimized size so that we don't spend huge amounts of
compile time trying to optimize initializers of gigabyte sizes) shouldn't be
a param.
Bootstrapped/regtested on x86_64-linux and i686-linux.
2021-11-04 Jakub Jelinek <ja...@redhat.com>
PR c++/102876
gcc/
* internal-fn.def (DYNAMIC_INIT_START, DYNAMIC_INIT_END): New internal
functions.
* internal-fn.c (expand_DYNAMIC_INIT_START, expand_DYNAMIC_INIT_END):
New functions.
* tree-pass.h (make_pass_dyninit): Declare.
* passes.def (pass_dyninit): Add after dce4.
* gimple-ssa-store-merging.c (pass_data_dyninit): New variable.
(class pass_dyninit): New type.
(pass_dyninit::execute): New method.
(make_pass_dyninit): New function.
gcc/cp/
* decl2.c (one_static_initialization_or_destruction): Emit
.DYNAMIC_INIT_START and .DYNAMIC_INIT_END internal calls around
dynamic initialization of variables that don't need a guard.
gcc/testsuite/
* g++.dg/opt/init3.C: New test.
--- gcc/internal-fn.def.jj 2021-11-02 09:05:47.029664211 +0100
+++ gcc/internal-fn.def 2021-11-02 12:40:38.702436113 +0100
@@ -367,6 +367,10 @@ DEF_INTERNAL_FN (PHI, 0, NULL)
automatic variable. */
DEF_INTERNAL_FN (DEFERRED_INIT, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
+/* Mark start and end of dynamic initialization of a variable. */
+DEF_INTERNAL_FN (DYNAMIC_INIT_START, ECF_LEAF | ECF_NOTHROW, ". r ")
+DEF_INTERNAL_FN (DYNAMIC_INIT_END, ECF_LEAF | ECF_NOTHROW, ". r ")
+
/* DIM_SIZE and DIM_POS return the size of a particular compute
dimension and the executing thread's position within that
dimension. DIM_POS is pure (and not const) so that it isn't
--- gcc/internal-fn.c.jj 2021-11-02 09:05:47.029664211 +0100
+++ gcc/internal-fn.c 2021-11-02 12:40:38.703436099 +0100
@@ -3485,6 +3485,16 @@ expand_CO_ACTOR (internal_fn, gcall *)
gcc_unreachable ();
}
+static void
+expand_DYNAMIC_INIT_START (internal_fn, gcall *)
+{
+}
+
+static void
+expand_DYNAMIC_INIT_END (internal_fn, gcall *)
+{
+}
+
/* Expand a call to FN using the operands in STMT. FN has a single
output operand and NARGS input operands. */
--- gcc/tree-pass.h.jj 2021-10-28 11:29:01.891721153 +0200
+++ gcc/tree-pass.h 2021-11-02 14:15:00.139185088 +0100
@@ -445,6 +445,7 @@ extern gimple_opt_pass *make_pass_cse_re
extern gimple_opt_pass *make_pass_cse_sincos (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_optimize_bswap (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_store_merging (gcc::context *ctxt);
+extern gimple_opt_pass *make_pass_dyninit (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_optimize_widening_mul (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_warn_function_return (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_warn_function_noreturn (gcc::context *ctxt);
--- gcc/passes.def.jj 2021-11-01 14:37:06.685853324 +0100
+++ gcc/passes.def 2021-11-02 14:23:47.836715821 +0100
@@ -261,6 +261,7 @@ along with GCC; see the file COPYING3.
NEXT_PASS (pass_tsan);
NEXT_PASS (pass_dse);
NEXT_PASS (pass_dce);
+ NEXT_PASS (pass_dyninit);
/* Pass group that runs when 1) enabled, 2) there are loops
in the function. Make sure to run pass_fix_loops before
to discover/remove loops before running the gate function
--- gcc/gimple-ssa-store-merging.c.jj 2021-09-01 12:06:19.488211919 +0200
+++ gcc/gimple-ssa-store-merging.c 2021-11-03 18:02:55.190015359 +0100
@@ -170,6 +170,8 @@
#include "optabs-tree.h"
#include "dbgcnt.h"
#include "selftest.h"
+#include "cgraph.h"
+#include "varasm.h"
/* The maximum size (in bits) of the stores this pass should generate. */
#define MAX_STORE_BITSIZE (BITS_PER_WORD)
@@ -5465,6 +5467,334 @@ pass_store_merging::execute (function *f
return 0;
}
+/* Pass to optimize C++ dynamic initialization. */
+
+const pass_data pass_data_dyninit = {
+ GIMPLE_PASS, /* type */
+ "dyninit", /* name */
+ OPTGROUP_NONE, /* optinfo_flags */
+ TV_GIMPLE_STORE_MERGING, /* tv_id */
+ PROP_ssa, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ 0, /* todo_flags_finish */
+};
+
+class pass_dyninit : public gimple_opt_pass
+{
+public:
+ pass_dyninit (gcc::context *ctxt)
+ : gimple_opt_pass (pass_data_dyninit, ctxt)
+ {
+ }
+
+ virtual bool
+ gate (function *fun)
+ {
+ return (DECL_ARTIFICIAL (fun->decl)
+ && DECL_STATIC_CONSTRUCTOR (fun->decl)
+ && optimize);
+ }
+
+ virtual unsigned int execute (function *);
+}; // class pass_dyninit
+
+unsigned int
+pass_dyninit::execute (function *fun)
+{
+ basic_block bb;
+ auto_vec<gimple *, 32> ifns;
+ hash_map<tree, gimple *> *map = NULL;
+ auto_vec<tree, 32> vars;
+ gimple **cur = NULL;
+ bool ssdf_calls = false;
+
+ FOR_EACH_BB_FN (bb, fun)
+ {
+ for (gimple_stmt_iterator gsi = gsi_after_labels (bb);
+ !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple *stmt = gsi_stmt (gsi);
+ if (is_gimple_debug (stmt))
+ continue;
+
+ /* The C++ FE can wrap dynamic initialization of certain
+ variables with a pair of iternal function calls, like:
+ .DYNAMIC_INIT_START (&b, 0);
+ b = 1;
+ .DYNAMIC_INIT_END (&b);
+
+ or
+ .DYNAMIC_INIT_START (&e, 1);
+ # DEBUG this => &e.f
+ MEM[(struct S *)&e + 4B] ={v} {CLOBBER};
+ MEM[(struct S *)&e + 4B].a = 1;
+ MEM[(struct S *)&e + 4B].b = 2;
+ MEM[(struct S *)&e + 4B].c = 3;
+ # DEBUG BEGIN_STMT
+ MEM[(struct S *)&e + 4B].d = 6;
+ # DEBUG this => NULL
+ .DYNAMIC_INIT_END (&e);
+
+ Verify if there are only stores of constants to the corresponding
+ variable or parts of that variable and if so, try to reconstruct
+ a static initializer from the static initializer if any and
+ the constant stores into the variable. This is permitted by
+ [basic.start.static]/3. */
+ if (is_gimple_call (stmt))
+ {
+ if (gimple_call_internal_p (stmt, IFN_DYNAMIC_INIT_START))
+ {
+ ifns.safe_push (stmt);
+ if (cur)
+ *cur = NULL;
+ tree arg = gimple_call_arg (stmt, 0);
+ gcc_assert (TREE_CODE (arg) == ADDR_EXPR
+ && DECL_P (TREE_OPERAND (arg, 0)));
+ tree var = TREE_OPERAND (arg, 0);
+ gcc_checking_assert (is_global_var (var));
+ varpool_node *node = varpool_node::get (var);
+ if (node == NULL
+ || node->in_other_partition
+ || TREE_ASM_WRITTEN (var)
+ || DECL_SIZE_UNIT (var) == NULL_TREE
+ || !tree_fits_uhwi_p (DECL_SIZE_UNIT (var))
+ || tree_to_uhwi (DECL_SIZE_UNIT (var)) > 1024
+ || TYPE_SIZE_UNIT (TREE_TYPE (var)) == NULL_TREE
+ || !tree_int_cst_equal (TYPE_SIZE_UNIT (TREE_TYPE (var)),
+ DECL_SIZE_UNIT (var)))
+ continue;
+ if (map == NULL)
+ map = new hash_map<tree, gimple *> (61);
+ bool existed_p;
+ cur = &map->get_or_insert (var, &existed_p);
+ if (existed_p)
+ {
+ /* Punt if we see more than one .DYNAMIC_INIT_START
+ internal call for the same variable. */
+ *cur = NULL;
+ cur = NULL;
+ }
+ else
+ {
+ *cur = stmt;
+ vars.safe_push (var);
+ }
+ continue;
+ }
+ else if (gimple_call_internal_p (stmt, IFN_DYNAMIC_INIT_END))
+ {
+ ifns.safe_push (stmt);
+ tree arg = gimple_call_arg (stmt, 0);
+ gcc_assert (TREE_CODE (arg) == ADDR_EXPR
+ && DECL_P (TREE_OPERAND (arg, 0)));
+ tree var = TREE_OPERAND (arg, 0);
+ gcc_checking_assert (is_global_var (var));
+ if (cur)
+ {
+ /* Punt if .DYNAMIC_INIT_END call argument doesn't
+ pair with .DYNAMIC_INIT_START. */
+ if (vars.last () != var)
+ *cur = NULL;
+ cur = NULL;
+ }
+ continue;
+ }
+
+ /* Punt if we see any artificial
+ __static_initialization_and_destruction_* calls, e.g. if
+ it would be partially inlined, because we wouldn't then see
+ all .DYNAMIC_INIT_* calls. */
+ tree fndecl = gimple_call_fndecl (stmt);
+ if (fndecl
+ && DECL_ARTIFICIAL (fndecl)
+ && DECL_NAME (fndecl)
+ && startswith (IDENTIFIER_POINTER (DECL_NAME (fndecl)),
+ "__static_initialization_and_destruction_"))
+ ssdf_calls = true;
+ }
+ if (cur)
+ {
+ if (store_valid_for_store_merging_p (stmt))
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ tree rhs = gimple_assign_rhs1 (stmt);
+ poly_int64 bitsize, bitpos;
+ HOST_WIDE_INT ibitsize, ibitpos;
+ machine_mode mode;
+ int unsignedp, reversep, volatilep = 0;
+ tree offset;
+ tree var = vars.last ();
+ if (rhs_valid_for_store_merging_p (rhs)
+ && get_inner_reference (lhs, &bitsize, &bitpos, &offset,
+ &mode, &unsignedp, &reversep,
+ &volatilep) == var
+ && !reversep
+ && !volatilep
+ && (offset == NULL_TREE || integer_zerop (offset))
+ && bitsize.is_constant (&ibitsize)
+ && bitpos.is_constant (&ibitpos)
+ && ibitpos >= 0
+ && ibitsize <= tree_to_shwi (DECL_SIZE (var))
+ && ibitsize + ibitpos <= tree_to_shwi (DECL_SIZE (var)))
+ continue;
+ }
+ *cur = NULL;
+ cur = NULL;
+ }
+ }
+ if (cur)
+ {
+ *cur = NULL;
+ cur = NULL;
+ }
+ }
+ if (map && !ssdf_calls)
+ {
+ for (tree var : vars)
+ {
+ gimple *g = *map->get (var);
+ if (g == NULL)
+ continue;
+ varpool_node *node = varpool_node::get (var);
+ node->get_constructor ();
+ tree init = DECL_INITIAL (var);
+ if (init == NULL)
+ init = build_zero_cst (TREE_TYPE (var));
+ gimple_stmt_iterator gsi = gsi_for_stmt (g);
+ unsigned char *buf = NULL;
+ unsigned int buf_size = tree_to_uhwi (DECL_SIZE_UNIT (var));
+ bool buf_valid = false;
+ do
+ {
+ gsi_next (&gsi);
+ gimple *stmt = gsi_stmt (gsi);
+ if (is_gimple_debug (stmt))
+ continue;
+ if (is_gimple_call (stmt))
+ break;
+ if (gimple_clobber_p (stmt))
+ continue;
+ tree lhs = gimple_assign_lhs (stmt);
+ tree rhs = gimple_assign_rhs1 (stmt);
+ if (lhs == var)
+ {
+ /* Simple assignment to the whole variable.
+ rhs is the initializer. */
+ buf_valid = false;
+ init = rhs;
+ continue;
+ }
+ poly_int64 bitsize, bitpos;
+ machine_mode mode;
+ int unsignedp, reversep, volatilep = 0;
+ tree offset;
+ get_inner_reference (lhs, &bitsize, &bitpos, &offset,
+ &mode, &unsignedp, &reversep, &volatilep);
+ HOST_WIDE_INT ibitsize = bitsize.to_constant ();
+ HOST_WIDE_INT ibitpos = bitpos.to_constant ();
+ if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN
+ || CHAR_BIT != 8
+ || BITS_PER_UNIT != 8)
+ {
+ g = NULL;
+ break;
+ }
+ if (!buf_valid)
+ {
+ if (buf == NULL)
+ buf = XNEWVEC (unsigned char, buf_size * 2);
+ memset (buf, 0, buf_size);
+ if (native_encode_initializer (init, buf, buf_size)
+ != (int) buf_size)
+ {
+ g = NULL;
+ break;
+ }
+ buf_valid = true;
+ }
+ /* Otherwise go through byte representation. */
+ if (!encode_tree_to_bitpos (rhs, buf, ibitsize,
+ ibitpos, buf_size))
+ {
+ g = NULL;
+ break;
+ }
+ }
+ while (1);
+ if (g == NULL)
+ {
+ XDELETE (buf);
+ continue;
+ }
+ if (buf_valid)
+ {
+ init = native_interpret_aggregate (TREE_TYPE (var), buf, 0,
+ buf_size);
+ if (init)
+ {
+ /* Verify the dynamic initialization doesn't e.g. set
+ some padding bits to non-zero by trying to encode
+ it again and comparing. */
+ memset (buf + buf_size, 0, buf_size);
+ if (native_encode_initializer (init, buf + buf_size,
+ buf_size) != (int) buf_size
+ || memcmp (buf, buf + buf_size, buf_size) != 0)
+ init = NULL_TREE;
+ }
+ }
+ XDELETE (buf);
+ if (!init || !initializer_constant_valid_p (init, TREE_TYPE (var)))
+ continue;
+ if (integer_nonzerop (gimple_call_arg (g, 1)))
+ TREE_READONLY (var) = 1;
+ if (dump_file)
+ {
+ fprintf (dump_file, "dynamic initialization of ");
+ print_generic_stmt (dump_file, var, TDF_SLIM);
+ fprintf (dump_file, " optimized into: ");
+ print_generic_stmt (dump_file, init, TDF_SLIM);
+ if (TREE_READONLY (var))
+ fprintf (dump_file, " and making it read-only\n");
+ fprintf (dump_file, "\n");
+ }
+ if (initializer_zerop (init))
+ DECL_INITIAL (var) = NULL_TREE;
+ else
+ DECL_INITIAL (var) = init;
+ gsi = gsi_for_stmt (g);
+ gsi_next (&gsi);
+ do
+ {
+ gimple *stmt = gsi_stmt (gsi);
+ if (is_gimple_debug (stmt))
+ {
+ gsi_next (&gsi);
+ continue;
+ }
+ if (is_gimple_call (stmt))
+ break;
+ /* Remove now all the stores for the dynamic initialization. */
+ unlink_stmt_vdef (stmt);
+ gsi_remove (&gsi, true);
+ if (gimple_vdef (stmt))
+ release_ssa_name (gimple_vdef (stmt));
+ }
+ while (1);
+ }
+ }
+ delete map;
+ for (gimple *g : ifns)
+ {
+ gimple_stmt_iterator gsi = gsi_for_stmt (g);
+ unlink_stmt_vdef (g);
+ gsi_remove (&gsi, true);
+ if (gimple_vdef (g))
+ release_ssa_name (gimple_vdef (g));
+ }
+ return 0;
+}
} // anon namespace
/* Construct and return a store merging pass object. */
@@ -5475,6 +5805,14 @@ make_pass_store_merging (gcc::context *c
return new pass_store_merging (ctxt);
}
+/* Construct and return a dyninit pass object. */
+
+gimple_opt_pass *
+make_pass_dyninit (gcc::context *ctxt)
+{
+ return new pass_dyninit (ctxt);
+}
+
#if CHECKING_P
namespace selftest {
--- gcc/cp/decl2.c.jj 2021-11-02 09:05:47.004664566 +0100
+++ gcc/cp/decl2.c 2021-11-03 17:18:11.395288518 +0100
@@ -4133,13 +4133,36 @@ one_static_initialization_or_destruction
{
if (init)
{
+ bool sanitize = sanitize_flags_p (SANITIZE_ADDRESS, decl);
+ if (optimize && guard == NULL_TREE && !sanitize)
+ {
+ tree t = build_fold_addr_expr (decl);
+ tree type = TREE_TYPE (decl);
+ tree is_const
+ = constant_boolean_node (TYPE_READONLY (type)
+ && !cp_has_mutable_p (type),
+ boolean_type_node);
+ t = build_call_expr_internal_loc (DECL_SOURCE_LOCATION (decl),
+ IFN_DYNAMIC_INIT_START,
+ void_type_node, 2, t,
+ is_const);
+ finish_expr_stmt (t);
+ }
finish_expr_stmt (init);
- if (sanitize_flags_p (SANITIZE_ADDRESS, decl))
+ if (sanitize)
{
varpool_node *vnode = varpool_node::get (decl);
if (vnode)
vnode->dynamically_initialized = 1;
}
+ else if (optimize && guard == NULL_TREE)
+ {
+ tree t = build_fold_addr_expr (decl);
+ t = build_call_expr_internal_loc (DECL_SOURCE_LOCATION (decl),
+ IFN_DYNAMIC_INIT_END,
+ void_type_node, 1, t);
+ finish_expr_stmt (t);
+ }
}
/* If we're using __cxa_atexit, register a function that calls the
--- gcc/testsuite/g++.dg/opt/init3.C.jj 2021-11-03 17:53:01.872472570 +0100
+++ gcc/testsuite/g++.dg/opt/init3.C 2021-11-03 17:52:57.484535115 +0100
@@ -0,0 +1,31 @@
+// PR c++/102876
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-dyninit" }
+// { dg-final { scan-tree-dump "dynamic initialization of b\[\n\r]* optimized
into: 1" "dyninit" } }
+// { dg-final { scan-tree-dump "dynamic initialization of e\[\n\r]* optimized
into: {.e=5, .f={.a=1, .b=2, .c=3, .d=6}, .g=6}\[\n\r]* and making it
read-only" "dyninit" } }
+// { dg-final { scan-tree-dump "dynamic initialization of f\[\n\r]* optimized
into: {.e=7, .f={.a=1, .b=2, .c=3, .d=6}, .g=1}" "dyninit" } }
+// { dg-final { scan-tree-dump "dynamic initialization of h\[\n\r]* optimized
into: {.h=8, .i={.a=1, .b=2, .c=3, .d=6}, .j=9}" "dyninit" } }
+// { dg-final { scan-tree-dump-times "dynamic initialization of " 4 "dyninit"
} }
+// { dg-final { scan-tree-dump-times "and making it read-only" 1 "dyninit" } }
+
+struct S { S () : a(1), b(2), c(3), d(4) { d += 2; } int a, b, c, d; };
+struct T { int e; S f; int g; };
+struct U { int h; mutable S i; int j; };
+extern int b;
+int foo (int &);
+int bar (int &);
+int baz () { return 1; }
+int qux () { return b = 2; }
+// Dynamic initialization of a shouldn't be optimized, foo can't be inlined.
+int a = foo (b);
+int b = baz ();
+// Likewise for c.
+int c = bar (b);
+// While qux is inlined, the dynamic initialization modifies another
+// variable, so punt for d as well.
+int d = qux ();
+const T e = { 5, S (), 6 };
+T f = { 7, S (), baz () };
+const T &g = e;
+const U h = { 8, S (), 9 };
+const U &i = h;
Jakub
