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verbose-asm.md

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生成有详细信息的汇编文件

例子

#include <stdio.h>

int main(void)
{
  int i;

  for (i = 0; i < 10; i++)
    printf("%d ", i);
  putchar ('\n');

  return 0;
}

技巧

使用-fverbose-asm选项就可以生成带有详细信息的汇编文件：

$ gcc -S -fverbose-asm foo.c
$ cat foo.s
	.file	"foo.c"
# GNU C (Ubuntu/Linaro 4.6.3-1ubuntu5) version 4.6.3 (x86_64-linux-gnu)
#	compiled by GNU C version 4.6.3, GMP version 5.0.2, MPFR version 3.1.0-p3, MPC version 0.9
# GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
# options passed:  -imultilib . -imultiarch x86_64-linux-gnu foo.c
# -mtune=generic -march=x86-64 -fverbose-asm -fstack-protector
# options enabled:  -fasynchronous-unwind-tables -fauto-inc-dec
# -fbranch-count-reg -fcommon -fdelete-null-pointer-checks -fdwarf2-cfi-asm
# -fearly-inlining -feliminate-unused-debug-types -ffunction-cse -fgcse-lm
# -fident -finline-functions-called-once -fira-share-save-slots
# -fira-share-spill-slots -fivopts -fkeep-static-consts
# -fleading-underscore -fmath-errno -fmerge-debug-strings
# -fmove-loop-invariants -fpeephole -fprefetch-loop-arrays
# -freg-struct-return -fsched-critical-path-heuristic
# -fsched-dep-count-heuristic -fsched-group-heuristic -fsched-interblock
# -fsched-last-insn-heuristic -fsched-rank-heuristic -fsched-spec
# -fsched-spec-insn-heuristic -fsched-stalled-insns-dep -fshow-column
# -fsigned-zeros -fsplit-ivs-in-unroller -fstack-protector
# -fstrict-volatile-bitfields -ftrapping-math -ftree-cselim -ftree-forwprop
# -ftree-loop-if-convert -ftree-loop-im -ftree-loop-ivcanon
# -ftree-loop-optimize -ftree-parallelize-loops= -ftree-phiprop -ftree-pta
# -ftree-reassoc -ftree-scev-cprop -ftree-slp-vectorize
# -ftree-vect-loop-version -funit-at-a-time -funwind-tables
# -fvect-cost-model -fverbose-asm -fzero-initialized-in-bss
# -m128bit-long-double -m64 -m80387 -maccumulate-outgoing-args
# -malign-stringops -mfancy-math-387 -mfp-ret-in-387 -mglibc -mieee-fp
# -mmmx -mno-sse4 -mpush-args -mred-zone -msse -msse2 -mtls-direct-seg-refs

# Compiler executable checksum: 75e879ed14f91af504f4150eadeaa0e6

	.section	.rodata
.LC0:
	.string	"%d "
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp	#
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp	#,
	.cfi_def_cfa_register 6
	subq	$16, %rsp	#,
	movl	$0, -4(%rbp)	#, i
	jmp	.L2	#
.L3:
	movl	$.LC0, %eax	#, D.2049
	movl	-4(%rbp), %edx	# i, tmp62
	movl	%edx, %esi	# tmp62,
	movq	%rax, %rdi	# D.2049,
	movl	$0, %eax	#,
	call	printf	#
	addl	$1, -4(%rbp)	#, i
.L2:
	cmpl	$9, -4(%rbp)	#, i
	jle	.L3	#,
	movl	$10, %edi	#,
	call	putchar	#
	movl	$0, %eax	#, D.2050
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3"
	.section	.note.GNU-stack,"",@progbits

可以看到，在汇编文件中给出了gcc所使用的具体选项，以及汇编指令操作数所对应的源程序（或中间代码）中的变量。

详情参见gcc手册

贡献者

xmj