¿Cómo eliminar el "ruido" de la salida del conjunto GCC / clang?
Quiero inspeccionar el resultado del ensamblaje de aplicarboost::variant
en mi código para ver qué llamadas intermedias están optimizada
Cuando compilo el siguiente ejemplo (con GCC 5.3 usandog++ -O3 -std=c++14 -S
), parece que el compilador optimiza todo y devuelve directamente 100:
(...)
main:
.LFB9320:
.cfi_startproc
movl $100, %eax
ret
.cfi_endproc
(...)
#include <boost/variant.hpp>
struct Foo
{
int get() { return 100; }
};
struct Bar
{
int get() { return 999; }
};
using Variant = boost::variant<Foo, Bar>;
int run(Variant v)
{
return boost::apply_visitor([](auto& x){return x.get();}, v);
}
int main()
{
Foo f;
return run(f);
}
Sin embargo, la salida del ensamblaje completo contiene mucho más que el extracto anterior, que para mí parece que nunca se llama. @ ¿Hay alguna manera de decirle a GCC / clang que elimine todo ese "ruido" y simplemente genere lo que realmente se llama cuando se ejecuta el programa?
full conjunto de salida:
.file "main1.cpp"
.section .rodata.str1.8,"aMS",@progbits,1
.align 8
.LC0:
.string "/opt/boost/include/boost/variant/detail/forced_return.hpp"
.section .rodata.str1.1,"aMS",@progbits,1
.LC1:
.string "false"
.section .text.unlikely._ZN5boost6detail7variant13forced_returnIvEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIvEET_v,comdat
.LCOLDB2:
.section .text._ZN5boost6detail7variant13forced_returnIvEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIvEET_v,comdat
.LHOTB2:
.p2align 4,,15
.weak _ZN5boost6detail7variant13forced_returnIvEET_v
.type _ZN5boost6detail7variant13forced_returnIvEET_v, @function
_ZN5boost6detail7variant13forced_returnIvEET_v:
.LFB1197:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
movl $_ZZN5boost6detail7variant13forced_returnIvEET_vE19__PRETTY_FUNCTION__, %ecx
movl $49, %edx
movl $.LC0, %esi
movl $.LC1, %edi
call __assert_fail
.cfi_endproc
.LFE1197:
.size _ZN5boost6detail7variant13forced_returnIvEET_v, .-_ZN5boost6detail7variant13forced_returnIvEET_v
.section .text.unlikely._ZN5boost6detail7variant13forced_returnIvEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIvEET_v,comdat
.LCOLDE2:
.section .text._ZN5boost6detail7variant13forced_returnIvEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIvEET_v,comdat
.LHOTE2:
.section .text.unlikely._ZN5boost6detail7variant13forced_returnIiEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIiEET_v,comdat
.LCOLDB3:
.section .text._ZN5boost6detail7variant13forced_returnIiEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIiEET_v,comdat
.LHOTB3:
.p2align 4,,15
.weak _ZN5boost6detail7variant13forced_returnIiEET_v
.type _ZN5boost6detail7variant13forced_returnIiEET_v, @function
_ZN5boost6detail7variant13forced_returnIiEET_v:
.LFB9757:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
movl $_ZZN5boost6detail7variant13forced_returnIiEET_vE19__PRETTY_FUNCTION__, %ecx
movl $39, %edx
movl $.LC0, %esi
movl $.LC1, %edi
call __assert_fail
.cfi_endproc
.LFE9757:
.size _ZN5boost6detail7variant13forced_returnIiEET_v, .-_ZN5boost6detail7variant13forced_returnIiEET_v
.section .text.unlikely._ZN5boost6detail7variant13forced_returnIiEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIiEET_v,comdat
.LCOLDE3:
.section .text._ZN5boost6detail7variant13forced_returnIiEET_v,"axG",@progbits,_ZN5boost6detail7variant13forced_returnIiEET_v,comdat
.LHOTE3:
.section .text.unlikely,"ax",@progbits
.LCOLDB4:
.text
.LHOTB4:
.p2align 4,,15
.globl _Z3runN5boost7variantI3FooJ3BarEEE
.type _Z3runN5boost7variantI3FooJ3BarEEE, @function
_Z3runN5boost7variantI3FooJ3BarEEE:
.LFB9310:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
movl (%rdi), %eax
cltd
xorl %edx, %eax
cmpl $19, %eax
ja .L7
jmp *.L9(,%rax,8)
.section .rodata
.align 8
.align 4
.L9:
.quad .L30
.quad .L10
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.quad .L7
.text
.p2align 4,,10
.p2align 3
.L7:
call _ZN5boost6detail7variant13forced_returnIiEET_v
.p2align 4,,10
.p2align 3
.L30:
movl $100, %eax
.L8:
addq $8, %rsp
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.p2align 4,,10
.p2align 3
.L10:
.cfi_restore_state
movl $999, %eax
jmp .L8
.cfi_endproc
.LFE9310:
.size _Z3runN5boost7variantI3FooJ3BarEEE, .-_Z3runN5boost7variantI3FooJ3BarEEE
.section .text.unlikely
.LCOLDE4:
.text
.LHOTE4:
.globl _Z3runN5boost7variantI3FooI3BarEEE
.set _Z3runN5boost7variantI3FooI3BarEEE,_Z3runN5boost7variantI3FooJ3BarEEE
.section .text.unlikely
.LCOLDB5:
.section .text.startup,"ax",@progbits
.LHOTB5:
.p2align 4,,15
.globl main
.type main, @function
main:
.LFB9320:
.cfi_startproc
movl $100, %eax
ret
.cfi_endproc
.LFE9320:
.size main, .-main
.section .text.unlikely
.LCOLDE5:
.section .text.startup
.LHOTE5:
.section .rodata
.align 32
.type _ZZN5boost6detail7variant13forced_returnIvEET_vE19__PRETTY_FUNCTION__, @object
.size _ZZN5boost6detail7variant13forced_returnIvEET_vE19__PRETTY_FUNCTION__, 58
_ZZN5boost6detail7variant13forced_returnIvEET_vE19__PRETTY_FUNCTION__:
.string "T boost::detail::variant::forced_return() [with T = void]"
.align 32
.type _ZZN5boost6detail7variant13forced_returnIiEET_vE19__PRETTY_FUNCTION__, @object
.size _ZZN5boost6detail7variant13forced_returnIiEET_vE19__PRETTY_FUNCTION__, 57
_ZZN5boost6detail7variant13forced_returnIiEET_vE19__PRETTY_FUNCTION__:
.string "T boost::detail::variant::forced_return() [with T = int]"
.ident "GCC: (Ubuntu 5.3.0-3ubuntu1~14.04) 5.3.0 20151204"
.section .note.GNU-stack,"",@progbits