标签:.section 标准 size end return rgs fst ref ext
http://blog.csdn.net/liujia2100/article/details/27236477
NEON:SIMD(Single Instruction Multiple Data 单指令多重数据) 指令集, 其针对多媒体和讯号处理程式具备标准化的加速能力。
VFP: (Vector Float Point), 向量浮点运算单元,arm11(s3c6410 支持VFPv2),Cortex-A8(s5pv210)支持VFPv3.
NEON和VFPv3 浮点协处理器共享寄存器组,所以在汇编时,指令是一样的。
编译选项:
-mfpu = name(neon or vfpvx)指定FPU 单元
-mfloat-abi = name(soft、hard、 softfp):指定软件浮点或硬件浮点或兼容软浮点调用接口
如果只指定 -mfpu,那么默认编译不会选择选择硬件浮点指令集
如果只指定 -mfloat-abi = hard或者softfp,那么编译会使用硬件浮点指令集
测试C文件
- int main(void)
- {
- float f1, f2, f3;
- f1 = 1.2;
- f2 = 1.3;
- f3 = f1 / f2;
- return 0;
- }
1、 arm-eabi-gcc -S hello.c -mfpu=neon
- .arch armv5te
- .fpu softvfp
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .global __aeabi_fdiv
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- stmfd sp!, {fp, lr}
- .save {fp, lr}
- .LCFI0:
- .setfp fp, sp, #4
- add fp, sp, #4
- .LCFI1:
- .pad #16
- sub sp, sp, #16
- .LCFI2:
- ldr r3, .L3 @ float
- str r3, [fp, #-16] @ float
- ldr r3, .L3+4 @ float
- str r3, [fp, #-12] @ float
- ldr r0, [fp, #-16] @ float
- ldr r1, [fp, #-12] @ float
- bl __aeabi_fdiv
- mov r3, r0
- str r3, [fp, #-8] @ float
- mov r3, #0
- mov r0, r3
- sub sp, fp, #4
- ldmfd sp!, {fp, pc}
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
2、 arm-eabi-gcc -S hello.c -mfpu=vfp
- .arch armv5te
- .fpu softvfp
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .global __aeabi_fdiv
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- stmfd sp!, {fp, lr}
- .save {fp, lr}
- .LCFI0:
- .setfp fp, sp, #4
- add fp, sp, #4
- .LCFI1:
- .pad #16
- sub sp, sp, #16
- .LCFI2:
- ldr r3, .L3 @ float
- str r3, [fp, #-16] @ float
- ldr r3, .L3+4 @ float
- str r3, [fp, #-12] @ float
- ldr r0, [fp, #-16] @ float
- ldr r1, [fp, #-12] @ float
- bl __aeabi_fdiv
- mov r3, r0
- str r3, [fp, #-8] @ float
- mov r3, #0
- mov r0, r3
- sub sp, fp, #4
- ldmfd sp!, {fp, pc}
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
可以看到上面两个例子,使用的是 .fpu softvfp
3、 arm-eabi-gcc -S hello.c -mfpu=neon -mfloat-abi=hard
- .arch armv5te
- .eabi_attribute 27, 3
- .eabi_attribute 28, 1
- .fpu neon
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- @ link register save eliminated.
- str fp, [sp, #-4]!
- .save {fp}
- .LCFI0:
- .setfp fp, sp, #0
- add fp, sp, #0
- .LCFI1:
- .pad #20
- sub sp, sp, #20
- .LCFI2:
- flds s15, .L3
- fsts s15, [fp, #-16]
- flds s15, .L3+4
- fsts s15, [fp, #-12]
- flds s14, [fp, #-16]
- flds s15, [fp, #-12]
- fdivs s15, s14, s15
- fsts s15, [fp, #-8]
- mov r3, #0
- mov r0, r3
- add sp, fp, #0
- ldmfd sp!, {fp}
- bx lr
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
4、 arm-eabi-gcc -S hello.c -mfpu=neon -mfloat-abi=softfp
- .arch armv5te
- .eabi_attribute 27, 3
- .fpu neon
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- @ link register save eliminated.
- str fp, [sp, #-4]!
- .save {fp}
- .LCFI0:
- .setfp fp, sp, #0
- add fp, sp, #0
- .LCFI1:
- .pad #20
- sub sp, sp, #20
- .LCFI2:
- flds s15, .L3
- fsts s15, [fp, #-16]
- flds s15, .L3+4
- fsts s15, [fp, #-12]
- flds s14, [fp, #-16]
- flds s15, [fp, #-12]
- fdivs s15, s14, s15
- fsts s15, [fp, #-8]
- mov r3, #0
- mov r0, r3
- add sp, fp, #0
- ldmfd sp!, {fp}
- bx lr
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
5、 arm-eabi-gcc -S hello.c -mfpu=vfpv3 -mfloat-abi=softfp
- .arch armv5te
- .eabi_attribute 27, 3
- .fpu vfpv3
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- @ link register save eliminated.
- str fp, [sp, #-4]!
- .save {fp}
- .LCFI0:
- .setfp fp, sp, #0
- add fp, sp, #0
- .LCFI1:
- .pad #20
- sub sp, sp, #20
- .LCFI2:
- flds s15, .L3
- fsts s15, [fp, #-16]
- flds s15, .L3+4
- fsts s15, [fp, #-12]
- flds s14, [fp, #-16]
- flds s15, [fp, #-12]
- fdivs s15, s14, s15
- fsts s15, [fp, #-8]
- mov r3, #0
- mov r0, r3
- add sp, fp, #0
- ldmfd sp!, {fp}
- bx lr
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
6、 arm-eabi-gcc -S hello.c -mfpu=vfpv3 -mfloat-abi=hard
- .arch armv5te
- .eabi_attribute 27, 3
- .eabi_attribute 28, 1
- .fpu vfpv3
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- @ link register save eliminated.
- str fp, [sp, #-4]!
- .save {fp}
- .LCFI0:
- .setfp fp, sp, #0
- add fp, sp, #0
- .LCFI1:
- .pad #20
- sub sp, sp, #20
- .LCFI2:
- flds s15, .L3
- fsts s15, [fp, #-16]
- flds s15, .L3+4
- fsts s15, [fp, #-12]
- flds s14, [fp, #-16]
- flds s15, [fp, #-12]
- fdivs s15, s14, s15
- fsts s15, [fp, #-8]
- mov r3, #0
- mov r0, r3
- add sp, fp, #0
- ldmfd sp!, {fp}
- bx lr
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
从上面可以看到,使用softfp和hard使用的指令集是一样的,都是硬件浮点, neon和vfp的区别,仅仅体现在.fpu vfpv3和.fpu neon.
7、 arm-eabi-gcc -S hello.c -mfloat-abi=hard
- .arch armv5te
- .eabi_attribute 27, 3
- .eabi_attribute 28, 1
- .fpu vfp
- .eabi_attribute 20, 1
- .eabi_attribute 21, 1
- .eabi_attribute 23, 3
- .eabi_attribute 24, 1
- .eabi_attribute 25, 1
- .eabi_attribute 26, 2
- .eabi_attribute 30, 6
- .eabi_attribute 18, 4
- .file "hello.c"
- .text
- .align 2
- .global main
- .type main, %function
- main:
- .fnstart
- .LFB0:
- @ args = 0, pretend = 0, frame = 16
- @ frame_needed = 1, uses_anonymous_args = 0
- @ link register save eliminated.
- str fp, [sp, #-4]!
- .save {fp}
- .LCFI0:
- .setfp fp, sp, #0
- add fp, sp, #0
- .LCFI1:
- .pad #20
- sub sp, sp, #20
- .LCFI2:
- flds s15, .L3
- fsts s15, [fp, #-16]
- flds s15, .L3+4
- fsts s15, [fp, #-12]
- flds s14, [fp, #-16]
- flds s15, [fp, #-12]
- fdivs s15, s14, s15
- fsts s15, [fp, #-8]
- mov r3, #0
- mov r0, r3
- add sp, fp, #0
- ldmfd sp!, {fp}
- bx lr
- .L4:
- .align 2
- .L3:
- .word 1067030938
- .word 1067869798
- .LFE0:
- .fnend
- .size main, .-main
- .ident "GCC: (Sourcery G++ Lite 2009q3-67) 4.4.1"
- .section .note.GNU-stack,"",%progbits
当直接使用-mfloat-abi=hard时,会默认使用.fpu vfp硬件浮点。
Linux下VFP NEON浮点编译
标签:.section 标准 size end return rgs fst ref ext
原文地址:http://www.cnblogs.com/leaven/p/6244697.html