New parameters to control stringop expansion libcall strategy
Michael V. Zolotukhin
michael.v.zolotukhin@gmail.com
Mon Aug 5 10:57:00 GMT 2013
Hi,
This is a really convenient option, thanks for working on it.
I can't approve it as I'm not a maintainer, but it looks ok to me,
except fot a small nitpicking: afair, comments should end with
dot-space-space.
Michael
On 04 Aug 20:01, Xinliang David Li wrote:
> The attached is a new patch implementing the stringop inline strategy
> control using two new -m options:
>
> -mmemcpy-strategy=
> -mmemset-strategy=
>
> See changes in doc/invoke.texi for description of the new options. Example:
> -mmemcpy-strategy=rep_8byte:64:unaligned,unrolled_loop:2048:unaligned,libcall:-1:unaligned
>
> tells compiler to inline memcpy using rep_8byte when the size is no
> larger than 64 byte, using unrolled_loop when size is no larger than
> 2048, and for size > 2048, using library call. In all cases,
> destination alignment adjustment is not done.
>
> Tested on x86-64/linux. Ok for trunk?
>
> thanks,
>
> David
>
> 2013-08-02 Xinliang David Li <davidxl@google.com>
>
> * config/i386/stringop.def: New file.
> * config/i386/stringop.opt: New file.
> * config/i386/i386-opts.h: Include stringopt.def.
> * config/i386/i386.opt: Include stringopt.opt.
> * config/i386/i386.c (ix86_option_override_internal):
> Override default size based stringop inline strategies
> with options.
> * config/i386/i386.c (ix86_parse_stringop_strategy_string):
> New function.
>
> 2013-08-04 Xinliang David Li <davidxl@google.com>
>
> * testsuite/gcc.target/i386/memcpy-strategy-1.c: New test.
> * testsuite/gcc.target/i386/memcpy-strategy-2.c: Ditto.
> * testsuite/gcc.target/i386/memset-strategy-1.c: Ditto.
> * testsuite/gcc.target/i386/memcpy-strategy-3.c: Ditto.
>
>
>
>
> On Fri, Aug 2, 2013 at 9:21 PM, Xinliang David Li <davidxl@google.com> wrote:
> > On x86_64, when the expected size of memcpy/memset is known (e.g, with
> > FDO), libcall strategy is used with the size is > 8192. This value is
> > hard coded, which makes it hard to do performance tuning. This patch
> > adds two new parameters to do that. Potential usage includes
> > per-application libcall strategy min-size tuning based on summary data
> > with FDO (e.g, instruction workset size).
> >
> > Bootstrap and tested on x86_64/linux. Ok for trunk?
> >
> > thanks,
> >
> > David
> >
> >
> > 2013-08-02 Xinliang David Li <davidxl@google.com>
> >
> > * params.def: New parameters.
> > * config/i386/i386.c (ix86_option_override_internal):
> > Override default libcall size limit with parameters.
> Index: config/i386/stringop.def
> ===================================================================
> --- config/i386/stringop.def (revision 0)
> +++ config/i386/stringop.def (revision 0)
> @@ -0,0 +1,42 @@
> +/* Definitions for option handling for IA-32.
> + Copyright (C) 2013 Free Software Foundation, Inc.
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify
> +it under the terms of the GNU General Public License as published by
> +the Free Software Foundation; either version 3, or (at your option)
> +any later version.
> +
> +GCC is distributed in the hope that it will be useful,
> +but WITHOUT ANY WARRANTY; without even the implied warranty of
> +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +GNU General Public License for more details.
> +
> +Under Section 7 of GPL version 3, you are granted additional
> +permissions described in the GCC Runtime Library Exception, version
> +3.1, as published by the Free Software Foundation.
> +
> +You should have received a copy of the GNU General Public License and
> +a copy of the GCC Runtime Library Exception along with this program;
> +see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> +<http://www.gnu.org/licenses/>. */
> +
> +DEF_ENUM
> +DEF_ALG (no_stringop, no_stringop)
> +DEF_ENUM
> +DEF_ALG (libcall, libcall)
> +DEF_ENUM
> +DEF_ALG (rep_prefix_1_byte, rep_byte)
> +DEF_ENUM
> +DEF_ALG (rep_prefix_4_byte, rep_4byte)
> +DEF_ENUM
> +DEF_ALG (rep_prefix_8_byte, rep_8byte)
> +DEF_ENUM
> +DEF_ALG (loop_1_byte, byte_loop)
> +DEF_ENUM
> +DEF_ALG (loop, loop)
> +DEF_ENUM
> +DEF_ALG (unrolled_loop, unrolled_loop)
> +DEF_ENUM
> +DEF_ALG (vector_loop, vector_loop)
> Index: config/i386/i386.opt
> ===================================================================
> --- config/i386/i386.opt (revision 201458)
> +++ config/i386/i386.opt (working copy)
> @@ -316,6 +316,14 @@ mstack-arg-probe
> Target Report Mask(STACK_PROBE) Save
> Enable stack probing
>
> +mmemcpy-strategy=
> +Target RejectNegative Joined Var(ix86_tune_memcpy_strategy)
> +Specify memcpy expansion strategy when expected size is known
> +
> +mmemset-strategy=
> +Target RejectNegative Joined Var(ix86_tune_memset_strategy)
> +Specify memset expansion strategy when expected size is known
> +
> mstringop-strategy=
> Target RejectNegative Joined Enum(stringop_alg) Var(ix86_stringop_alg) Init(no_stringop)
> Chose strategy to generate stringop using
> Index: config/i386/stringop.opt
> ===================================================================
> --- config/i386/stringop.opt (revision 0)
> +++ config/i386/stringop.opt (revision 0)
> @@ -0,0 +1,36 @@
> +/* Definitions for option handling for IA-32.
> + Copyright (C) 2013 Free Software Foundation, Inc.
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify
> +it under the terms of the GNU General Public License as published by
> +the Free Software Foundation; either version 3, or (at your option)
> +any later version.
> +
> +GCC is distributed in the hope that it will be useful,
> +but WITHOUT ANY WARRANTY; without even the implied warranty of
> +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +GNU General Public License for more details.
> +
> +Under Section 7 of GPL version 3, you are granted additional
> +permissions described in the GCC Runtime Library Exception, version
> +3.1, as published by the Free Software Foundation.
> +
> +You should have received a copy of the GNU General Public License and
> +a copy of the GCC Runtime Library Exception along with this program;
> +see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> +<http://www.gnu.org/licenses/>. */
> +
> +Enum(stringop_alg) String(rep_byte) Value(rep_prefix_1_byte)
> +
> +#undef DEF_ENUM
> +#define DEF_ENUM EnumValue
> +
> +#undef DEF_ALG
> +#define DEF_ALG(alg, name) Enum(stringop_alg) String(name) Value(alg)
> +
> +#include "stringop.def"
> +
> +#undef DEF_ENUM
> +#undef DEF_ALG
> Index: config/i386/i386.c
> ===================================================================
> --- config/i386/i386.c (revision 201458)
> +++ config/i386/i386.c (working copy)
> @@ -156,7 +156,7 @@ struct processor_costs ix86_size_cost =
> };
>
> /* Processor costs (relative to an add) */
> -static const
> +static
> struct processor_costs i386_cost = { /* 386 specific costs */
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -226,7 +226,7 @@ struct processor_costs i386_cost = { /*
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs i486_cost = { /* 486 specific costs */
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -298,7 +298,7 @@ struct processor_costs i486_cost = { /*
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs pentium_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -368,7 +368,7 @@ struct processor_costs pentium_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs pentiumpro_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -447,7 +447,7 @@ struct processor_costs pentiumpro_cost =
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs geode_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -518,7 +518,7 @@ struct processor_costs geode_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs k6_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (2), /* cost of a lea instruction */
> @@ -591,7 +591,7 @@ struct processor_costs k6_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs athlon_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (2), /* cost of a lea instruction */
> @@ -664,7 +664,7 @@ struct processor_costs athlon_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs k8_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (2), /* cost of a lea instruction */
> @@ -1265,7 +1265,7 @@ struct processor_costs btver2_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs pentium4_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (3), /* cost of a lea instruction */
> @@ -1336,7 +1336,7 @@ struct processor_costs pentium4_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs nocona_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1), /* cost of a lea instruction */
> @@ -1409,7 +1409,7 @@ struct processor_costs nocona_cost = {
> 1, /* cond_not_taken_branch_cost. */
> };
>
> -static const
> +static
> struct processor_costs atom_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1) + 1, /* cost of a lea instruction */
> @@ -1556,7 +1556,7 @@ struct processor_costs slm_cost = {
> };
>
> /* Generic64 should produce code tuned for Nocona and K8. */
> -static const
> +static
> struct processor_costs generic64_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> /* On all chips taken into consideration lea is 2 cycles and more. With
> @@ -1635,7 +1635,7 @@ struct processor_costs generic64_cost =
> };
>
> /* core_cost should produce code tuned for Core familly of CPUs. */
> -static const
> +static
> struct processor_costs core_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> /* On all chips taken into consideration lea is 2 cycles and more. With
> @@ -1717,7 +1717,7 @@ struct processor_costs core_cost = {
>
> /* Generic32 should produce code tuned for PPro, Pentium4, Nocona,
> Athlon and K8. */
> -static const
> +static
> struct processor_costs generic32_cost = {
> COSTS_N_INSNS (1), /* cost of an add instruction */
> COSTS_N_INSNS (1) + 1, /* cost of a lea instruction */
> @@ -2900,6 +2900,150 @@ ix86_debug_options (void)
>
> return;
> }
> +
> +static const char *stringop_alg_names[] = {
> +#define DEF_ENUM
> +#define DEF_ALG(alg, name) #name,
> +#include "stringop.def"
> +#undef DEF_ENUM
> +#undef DEF_ALG
> +};
> +
> +/* Parse parameter string passed to -mmemcpy-strategy= or -mmemset-strategy=.
> + The string is of the following form (or comma separated list of it):
> +
> + strategy_alg:max_size:[align|noalign]
> +
> + where the full size range for the strategy is either [0, max_size] or
> + [min_size, max_size], in which min_size is the max_size + 1 of the
> + preceding range. The last size range must have max_size == -1.
> +
> + Examples:
> +
> + 1.
> + -mmemcpy-strategy=libcall:-1:noalign
> +
> + this is equivalent to (for known size memcpy) -mstringop-strategy=libcall
> +
> +
> + 2.
> + -mmemset-strategy=rep_8byte:16:noalign,vector_loop:2048:align,libcall:-1:noalign
> +
> + This is to tell the compiler to use the following strategy for memset
> + 1) when the expected size is between [1, 16], use rep_8byte strategy;
> + 2) when the size is between [17, 2048], use vector_loop;
> + 3) when the size is > 2048, use libcall.
> +
> +*/
> +
> +struct stringop_size_range
> +{
> + int min;
> + int max;
> + stringop_alg alg;
> + bool noalign;
> +};
> +
> +static void
> +ix86_parse_stringop_strategy_string (char *strategy_str, bool is_memset)
> +{
> + const struct stringop_algs *default_algs;
> + stringop_size_range input_ranges[MAX_STRINGOP_ALGS];
> + char *curr_range_str, *next_range_str;
> + int i = 0, n = 0;
> +
> + if (is_memset)
> + default_algs = &ix86_cost->memset[TARGET_64BIT != 0];
> + else
> + default_algs = &ix86_cost->memcpy[TARGET_64BIT != 0];
> +
> + curr_range_str = strategy_str;
> +
> + do {
> +
> + int mins, maxs;
> + stringop_alg alg;
> + char alg_name[128];
> + char align[16];
> +
> + next_range_str = strchr (curr_range_str, ',');
> + if (next_range_str)
> + *next_range_str++ = '\0';
> +
> + if (3 != sscanf (curr_range_str, "%[^:]:%d:%s", alg_name, &maxs, align))
> + {
> + warning (0, "Wrong arg %s to option %s", curr_range_str,
> + is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> +
> + if (n > 0 && (maxs < (mins = input_ranges[n - 1].max + 1) && maxs != -1))
> + {
> + warning (0, "Size ranges of option %s should be increasing",
> + is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> +
> + for (i = 0; i < last_alg; i++)
> + {
> + if (!strcmp (alg_name, stringop_alg_names[i]))
> + {
> + alg = (stringop_alg) i;
> + break;
> + }
> + }
> +
> + if (i == last_alg)
> + {
> + warning (0, "Wrong stringop strategy name %s specified for option %s",
> + alg_name,
> + is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> +
> + input_ranges[n].min = mins;
> + input_ranges[n].max = maxs;
> + input_ranges[n].alg = alg;
> + if (!strcmp (align, "align"))
> + input_ranges[n].noalign = false;
> + else if (!strcmp (align, "noalign"))
> + input_ranges[n].noalign = true;
> + else
> + {
> + warning (0, "Unknown alignment %s specified for option %s",
> + align, is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> + n++;
> + curr_range_str = next_range_str;
> + } while (curr_range_str);
> +
> + if (input_ranges[n - 1].max != -1)
> + {
> + warning (0, "The max value for the last size range should be -1"
> + " for option %s",
> + is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> +
> + if (n > MAX_STRINGOP_ALGS)
> + {
> + warning (0, "Too many size ranges specified in option %s",
> + is_memset ? "-mmemset_strategy=" : "-mmemcpy_strategy=");
> + return;
> + }
> +
> + /* Now override the default algs array */
> + for (i = 0; i < n; i++)
> + {
> + *const_cast<int *>(&default_algs->size[i].max) = input_ranges[i].max;
> + *const_cast<stringop_alg *>(&default_algs->size[i].alg)
> + = input_ranges[i].alg;
> + *const_cast<int *>(&default_algs->size[i].noalign)
> + = input_ranges[i].noalign;
> + }
> +}
> +
>
> /* Override various settings based on options. If MAIN_ARGS_P, the
> options are from the command line, otherwise they are from
> @@ -4021,6 +4165,21 @@ ix86_option_override_internal (bool main
> /* Handle stack protector */
> if (!global_options_set.x_ix86_stack_protector_guard)
> ix86_stack_protector_guard = TARGET_HAS_BIONIC ? SSP_GLOBAL : SSP_TLS;
> +
> + /* Handle -mmemcpy-strategy= and -mmemset-strategy= */
> + if (ix86_tune_memcpy_strategy)
> + {
> + char *str = xstrdup (ix86_tune_memcpy_strategy);
> + ix86_parse_stringop_strategy_string (str, false);
> + free (str);
> + }
> +
> + if (ix86_tune_memset_strategy)
> + {
> + char *str = xstrdup (ix86_tune_memset_strategy);
> + ix86_parse_stringop_strategy_string (str, true);
> + free (str);
> + }
> }
>
> /* Implement the TARGET_OPTION_OVERRIDE hook. */
> @@ -22903,6 +23062,7 @@ ix86_expand_movmem (rtx dst, rtx src, rt
> {
> case libcall:
> case no_stringop:
> + case last_alg:
> gcc_unreachable ();
> case loop_1_byte:
> need_zero_guard = true;
> @@ -23093,6 +23253,7 @@ ix86_expand_movmem (rtx dst, rtx src, rt
> {
> case libcall:
> case no_stringop:
> + case last_alg:
> gcc_unreachable ();
> case loop_1_byte:
> case loop:
> @@ -23304,6 +23465,7 @@ ix86_expand_setmem (rtx dst, rtx count_e
> {
> case libcall:
> case no_stringop:
> + case last_alg:
> gcc_unreachable ();
> case loop:
> need_zero_guard = true;
> @@ -23481,6 +23643,7 @@ ix86_expand_setmem (rtx dst, rtx count_e
> {
> case libcall:
> case no_stringop:
> + case last_alg:
> gcc_unreachable ();
> case loop_1_byte:
> case loop:
> Index: config/i386/i386-opts.h
> ===================================================================
> --- config/i386/i386-opts.h (revision 201458)
> +++ config/i386/i386-opts.h (working copy)
> @@ -28,15 +28,17 @@ see the files COPYING3 and COPYING.RUNTI
> /* Algorithm to expand string function with. */
> enum stringop_alg
> {
> - no_stringop,
> - libcall,
> - rep_prefix_1_byte,
> - rep_prefix_4_byte,
> - rep_prefix_8_byte,
> - loop_1_byte,
> - loop,
> - unrolled_loop,
> - vector_loop
> +#undef DEF_ENUM
> +#define DEF_ENUM
> +
> +#undef DEF_ALG
> +#define DEF_ALG(alg, name) alg,
> +
> +#include "stringop.def"
> +last_alg
> +
> +#undef DEF_ENUM
> +#undef DEF_ALG
> };
>
> /* Available call abi. */
> Index: doc/invoke.texi
> ===================================================================
> --- doc/invoke.texi (revision 201458)
> +++ doc/invoke.texi (working copy)
> @@ -649,6 +649,7 @@ Objective-C and Objective-C++ Dialects}.
> -mbmi2 -mrtm -mlwp -mthreads @gol
> -mno-align-stringops -minline-all-stringops @gol
> -minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol
> +-mmemcpy-strategy=@var{strategy} -mmemset-strategy=@var{strategy}
> -mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
> -m96bit-long-double -mlong-double-64 -mlong-double-80 @gol
> -mregparm=@var{num} -msseregparm @gol
> @@ -14598,6 +14599,24 @@ Expand into an inline loop.
> Always use a library call.
> @end table
>
> +@item -mmemcpy-strategy=@var{strategy}
> +@opindex mmemcpy-strategy=@var{strategy}
> +Override the internal decision heuristic to decide if @code{__builtin_memcpy}
> +should be inlined and what inline algorithm to use when the expected size
> +of the copy operation is known. @var{strategy}
> +is a comma-separated list of @var{alg}:@var{max_size}:@var{dest_align} triplets.
> +@var{alg} is specified in @option{-mstringop-strategy}, @var{max_size} specifies
> +the max byte size with which inline algorithm @var{alg} is allowed. For the last
> +triplet, the @var{max_size} must be @code{-1}. The @var{max_size} of the triplets
> +in the list must be specified in increasing order. The minimal byte size for
> +@var{alg} is @code{0} for the first triplet and @code{@var{max_size} + 1} of the
> +preceding range.
> +
> +@item -mmemset-strategy=@var{strategy}
> +@opindex mmemset-strategy=@var{strategy}
> +The option is similar to @option{-mmemcpy-strategy=} except that it is to control
> +@code{__builtin_memset} expansion.
> +
> @item -momit-leaf-frame-pointer
> @opindex momit-leaf-frame-pointer
> Don't keep the frame pointer in a register for leaf functions. This
> Index: testsuite/gcc.target/i386/memcpy-strategy-1.c
> ===================================================================
> --- testsuite/gcc.target/i386/memcpy-strategy-1.c (revision 0)
> +++ testsuite/gcc.target/i386/memcpy-strategy-1.c (revision 0)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=atom -mmemcpy-strategy=vector_loop:-1:align" } */
> +/* { dg-final { scan-assembler-times "movdqa" 8 { target { ! { ia32 } } } } } */
> +/* { dg-final { scan-assembler-times "movdqa" 4 { target { ia32 } } } } */
> +
> +char a[2048];
> +char b[2048];
> +void t (void)
> +{
> + __builtin_memcpy (a, b, 2048);
> +}
> +
> Index: testsuite/gcc.target/i386/memcpy-strategy-2.c
> ===================================================================
> --- testsuite/gcc.target/i386/memcpy-strategy-2.c (revision 0)
> +++ testsuite/gcc.target/i386/memcpy-strategy-2.c (revision 0)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=atom -mmemcpy-strategy=vector_loop:3000:align,libcall:-1:align" } */
> +/* { dg-final { scan-assembler-times "movdqa" 8 { target { ! { ia32 } } } } } */
> +/* { dg-final { scan-assembler-times "movdqa" 4 { target { ia32 } } } } */
> +
> +char a[2048];
> +char b[2048];
> +void t (void)
> +{
> + __builtin_memcpy (a, b, 2048);
> +}
> +
> Index: testsuite/gcc.target/i386/memset-strategy-1.c
> ===================================================================
> --- testsuite/gcc.target/i386/memset-strategy-1.c (revision 0)
> +++ testsuite/gcc.target/i386/memset-strategy-1.c (revision 0)
> @@ -0,0 +1,10 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=atom -mmemset-strategy=libcall:-1:align" } */
> +/* { dg-final { scan-assembler-times "memset" 2 } } */
> +
> +char a[2048];
> +void t (void)
> +{
> + __builtin_memset (a, 1, 2048);
> +}
> +
> Index: testsuite/gcc.target/i386/memcpy-strategy-3.c
> ===================================================================
> --- testsuite/gcc.target/i386/memcpy-strategy-3.c (revision 0)
> +++ testsuite/gcc.target/i386/memcpy-strategy-3.c (revision 0)
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=atom -mmemcpy-strategy=vector_loop:2000:align,libcall:-1:align" } */
> +/* { dg-final { scan-assembler-times "memcpy" 2 } } */
> +
> +char a[2048];
> +char b[2048];
> +void t (void)
> +{
> + __builtin_memcpy (a, b, 2048);
> +}
> +
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