整数除法对照表(变量/2的幂)

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前言

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试验代码

// hw.cpp : Defines the entry point for the console application.// 整数除法对照表(变量/2的幂)// 特殊处理// a / 2^0// a / 2^1// a / 2^31// 其他都符合公式// 变量除以2的幂 公式: 对零取整[X / 2^n] = 下取整[(x + 2^n - 1)/2^n]#include "stdafx.h"#include <stdlib.h>#include <stdio.h>int fn_div_2_0(int a);int fn_div_2_1(int a);int fn_div_2_2(int a);int fn_div_2_3(int a);int fn_div_2_4(int a);int fn_div_2_5(int a);int fn_div_2_6(int a);int fn_div_2_7(int a);int fn_div_2_8(int a);int fn_div_2_9(int a);int fn_div_2_10(int a);int fn_div_2_11(int a);int fn_div_2_12(int a);int fn_div_2_13(int a);int fn_div_2_14(int a);int fn_div_2_15(int a);int fn_div_2_16(int a);int fn_div_2_17(int a);int fn_div_2_18(int a);int fn_div_2_19(int a);int fn_div_2_20(int a);int fn_div_2_21(int a);int fn_div_2_22(int a);int fn_div_2_23(int a);int fn_div_2_24(int a);int fn_div_2_25(int a);int fn_div_2_26(int a);int fn_div_2_27(int a);int fn_div_2_28(int a);int fn_div_2_29(int a);int fn_div_2_30(int a);int fn_div_2_31(int a);int main(int argc, char* argv[]){    printf("argc = %d\r\n", argc);    if (argc > 1) {        printf("agrv[1] = %s\r\n", argv[1]);    }    int a = (argc > 1) ? atoi(argv[1]) : 2147483648;    printf("%d\r\n", fn_div_2_0(a));    printf("%d\r\n", fn_div_2_1(a));    printf("%d\r\n", fn_div_2_2(a));    printf("%d\r\n", fn_div_2_3(a));    printf("%d\r\n", fn_div_2_4(a));    printf("%d\r\n", fn_div_2_5(a));    printf("%d\r\n", fn_div_2_6(a));    printf("%d\r\n", fn_div_2_7(a));    printf("%d\r\n", fn_div_2_8(a));    printf("%d\r\n", fn_div_2_9(a));    printf("%d\r\n", fn_div_2_10(a));    printf("%d\r\n", fn_div_2_11(a));    printf("%d\r\n", fn_div_2_12(a));    printf("%d\r\n", fn_div_2_13(a));    printf("%d\r\n", fn_div_2_14(a));    printf("%d\r\n", fn_div_2_15(a));    printf("%d\r\n", fn_div_2_16(a));    printf("%d\r\n", fn_div_2_17(a));    printf("%d\r\n", fn_div_2_18(a));    printf("%d\r\n", fn_div_2_19(a));    printf("%d\r\n", fn_div_2_20(a));    printf("%d\r\n", fn_div_2_21(a));    printf("%d\r\n", fn_div_2_22(a));    printf("%d\r\n", fn_div_2_23(a));    printf("%d\r\n", fn_div_2_24(a));    printf("%d\r\n", fn_div_2_25(a));    printf("%d\r\n", fn_div_2_26(a));    printf("%d\r\n", fn_div_2_27(a));    printf("%d\r\n", fn_div_2_28(a));    printf("%d\r\n", fn_div_2_29(a));    printf("%d\r\n", fn_div_2_30(a));    printf("%d\r\n", fn_div_2_31(a));    printf("END\r\n");    system ("pause");    return 0;}int fn_div_2_0(int a) {    return a / 1;// 004012E0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004012E4  \.  C3            retn}int fn_div_2_1(int a) {    return a / 2;// 004012F0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004012F4  |.  99            cdq// 004012F5  |.  2BC2          sub     eax, edx// 004012F7  |.  D1F8          sar     eax, 1// 004012F9  \.  C3            retn}int fn_div_2_2(int a) {    return a / 4;// 00401300 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401304  |.  99            cdq// 00401305  |.  83E2 03       and     edx, 3// 00401308  |.  03C2          add     eax, edx// 0040130A  |.  C1F8 02       sar     eax, 2// 0040130D  \.  C3            retn}int fn_div_2_3(int a) {    return a / 8;// 00401310 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401314  |.  99            cdq// 00401315  |.  83E2 07       and     edx, 7// 00401318  |.  03C2          add     eax, edx// 0040131A  |.  C1F8 03       sar     eax, 3// 0040131D  \.  C3            retn}int fn_div_2_4(int a) {    return a / 16;// 00401320 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401324  |.  99            cdq// 00401325  |.  83E2 0F       and     edx, 0F// 00401328  |.  03C2          add     eax, edx// 0040132A  |.  C1F8 04       sar     eax, 4// 0040132D  \.  C3            retn}int fn_div_2_5(int a) {    return a / 32;// 00401330 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401334  |.  99            cdq// 00401335  |.  83E2 1F       and     edx, 1F// 00401338  |.  03C2          add     eax, edx// 0040133A  |.  C1F8 05       sar     eax, 5// 0040133D  \.  C3            retn}int fn_div_2_6(int a) {    return a / 64;// 00401340 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401344  |.  99            cdq// 00401345  |.  83E2 3F       and     edx, 3F// 00401348  |.  03C2          add     eax, edx// 0040134A  |.  C1F8 06       sar     eax, 6// 0040134D  \.  C3            retn}int fn_div_2_7(int a) {    return a / 128;// 00401350 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401354  |.  99            cdq// 00401355  |.  83E2 7F       and     edx, 7F// 00401358  |.  03C2          add     eax, edx// 0040135A  |.  C1F8 07       sar     eax, 7// 0040135D  \.  C3            retn}int fn_div_2_8(int a) {    return a / 256;// 00401360 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401364  |.  99            cdq// 00401365  |.  81E2 FF000000 and     edx, 0FF// 0040136B  |.  03C2          add     eax, edx// 0040136D  |.  C1F8 08       sar     eax, 8// 00401370  \.  C3            retn}int fn_div_2_9(int a) {    return a / 512;// 00401380 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401384  |.  99            cdq// 00401385  |.  81E2 FF010000 and     edx, 1FF// 0040138B  |.  03C2          add     eax, edx// 0040138D  |.  C1F8 09       sar     eax, 9// 00401390  \.  C3            retn}int fn_div_2_10(int a) {    return a / 1024;// 004013A0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004013A4  |.  99            cdq// 004013A5  |.  81E2 FF030000 and     edx, 3FF// 004013AB  |.  03C2          add     eax, edx// 004013AD  |.  C1F8 0A       sar     eax, 0A// 004013B0  \.  C3            retn}int fn_div_2_11(int a) {    return a / 2048;// 004013C0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004013C4  |.  99            cdq// 004013C5  |.  81E2 FF070000 and     edx, 7FF// 004013CB  |.  03C2          add     eax, edx// 004013CD  |.  C1F8 0B       sar     eax, 0B// 004013D0  \.  C3            retn}int fn_div_2_12(int a) {    return a / 4096;// 004013E0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004013E4  |.  99            cdq// 004013E5  |.  81E2 FF0F0000 and     edx, 0FFF// 004013EB  |.  03C2          add     eax, edx// 004013ED  |.  C1F8 0C       sar     eax, 0C// 004013F0  \.  C3            retn}int fn_div_2_13(int a) {    return a / 8192;// 00401400 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401404  |.  99            cdq// 00401405  |.  81E2 FF1F0000 and     edx, 1FFF// 0040140B  |.  03C2          add     eax, edx// 0040140D  |.  C1F8 0D       sar     eax, 0D// 00401410  \.  C3            retn}int fn_div_2_14(int a) {    return a / 16384;// 00401420 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401424  |.  99            cdq// 00401425  |.  81E2 FF3F0000 and     edx, 3FFF// 0040142B  |.  03C2          add     eax, edx// 0040142D  |.  C1F8 0E       sar     eax, 0E// 00401430  \.  C3            retn}int fn_div_2_15(int a) {    return a / 32768;// 00401440 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401444  |.  99            cdq// 00401445  |.  81E2 FF7F0000 and     edx, 7FFF// 0040144B  |.  03C2          add     eax, edx// 0040144D  |.  C1F8 0F       sar     eax, 0F// 00401450  \.  C3            retn}int fn_div_2_16(int a) {    return a / 65536;// 00401460 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401464  |.  99            cdq// 00401465  |.  81E2 FFFF0000 and     edx, 0FFFF// 0040146B  |.  03C2          add     eax, edx// 0040146D  |.  C1F8 10       sar     eax, 10// 00401470  \.  C3            retn}int fn_div_2_17(int a) {    return a / 131072;// 00401480 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401484  |.  99            cdq// 00401485  |.  81E2 FFFF0100 and     edx, 1FFFF// 0040148B  |.  03C2          add     eax, edx// 0040148D  |.  C1F8 11       sar     eax, 11// 00401490  \.  C3            retn}int fn_div_2_18(int a) {    return a / 262144;// 004014A0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004014A4  |.  99            cdq// 004014A5  |.  81E2 FFFF0300 and     edx, 3FFFF// 004014AB  |.  03C2          add     eax, edx// 004014AD  |.  C1F8 12       sar     eax, 12// 004014B0  \.  C3            retn}int fn_div_2_19(int a) {    return a / 524288;// 004014C0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004014C4  |.  99            cdq// 004014C5  |.  81E2 FFFF0700 and     edx, 7FFFF// 004014CB  |.  03C2          add     eax, edx// 004014CD  |.  C1F8 13       sar     eax, 13// 004014D0  \.  C3            retn}int fn_div_2_20(int a) {    return a / 1048576;// 004014E0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004014E4  |.  99            cdq// 004014E5  |.  81E2 FFFF0F00 and     edx, 0FFFFF// 004014EB  |.  03C2          add     eax, edx// 004014ED  |.  C1F8 14       sar     eax, 14// 004014F0  \.  C3            retn}int fn_div_2_21(int a) {    return a / 2097152;// 00401500 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401504  |.  99            cdq// 00401505  |.  81E2 FFFF1F00 and     edx, 1FFFFF// 0040150B  |.  03C2          add     eax, edx// 0040150D  |.  C1F8 15       sar     eax, 15// 00401510  \.  C3            retn}int fn_div_2_22(int a) {    return a / 4194304;// 00401520 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401524  |.  99            cdq// 00401525  |.  81E2 FFFF3F00 and     edx, 3FFFFF// 0040152B  |.  03C2          add     eax, edx// 0040152D  |.  C1F8 16       sar     eax, 16// 00401530  \.  C3            retn}int fn_div_2_23(int a) {    return a / 8388608;// 00401540 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401544  |.  99            cdq// 00401545  |.  81E2 FFFF7F00 and     edx, 7FFFFF// 0040154B  |.  03C2          add     eax, edx// 0040154D  |.  C1F8 17       sar     eax, 17// 00401550  \.  C3            retn}int fn_div_2_24(int a) {    return a / 16777216;// 00401560 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401564  |.  99            cdq// 00401565  |.  81E2 FFFFFF00 and     edx, 0FFFFFF// 0040156B  |.  03C2          add     eax, edx// 0040156D  |.  C1F8 18       sar     eax, 18// 00401570  \.  C3            retn}int fn_div_2_25(int a) {    return a / 33554432;// 00401580 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401584  |.  99            cdq// 00401585  |.  81E2 FFFFFF01 and     edx, 1FFFFFF// 0040158B  |.  03C2          add     eax, edx// 0040158D  |.  C1F8 19       sar     eax, 19// 00401590  \.  C3            retn}int fn_div_2_26(int a) {    return a / 67108864;// 004015A0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004015A4  |.  99            cdq// 004015A5  |.  81E2 FFFFFF03 and     edx, 3FFFFFF// 004015AB  |.  03C2          add     eax, edx// 004015AD  |.  C1F8 1A       sar     eax, 1A// 004015B0  \.  C3            retn}int fn_div_2_27(int a) {    return a / 134217728;// 004015C0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004015C4  |.  99            cdq// 004015C5  |.  81E2 FFFFFF07 and     edx, 7FFFFFF// 004015CB  |.  03C2          add     eax, edx// 004015CD  |.  C1F8 1B       sar     eax, 1B// 004015D0  \.  C3            retn}int fn_div_2_28(int a) {    return a / 268435456;// 004015E0 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 004015E4  |.  99            cdq// 004015E5  |.  81E2 FFFFFF0F and     edx, 0FFFFFFF// 004015EB  |.  03C2          add     eax, edx// 004015ED  |.  C1F8 1C       sar     eax, 1C// 004015F0  \.  C3            retn}int fn_div_2_29(int a) {    return a / 536870912;// 00401600 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401604  |.  99            cdq// 00401605  |.  81E2 FFFFFF1F and     edx, 1FFFFFFF// 0040160B  |.  03C2          add     eax, edx// 0040160D  |.  C1F8 1D       sar     eax, 1D// 00401610  \.  C3            retn}int fn_div_2_30(int a) {    return a / 1073741824;// 00401620 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401624  |.  99            cdq// 00401625  |.  81E2 FFFFFF3F and     edx, 3FFFFFFF// 0040162B  |.  03C2          add     eax, edx// 0040162D  |.  C1F8 1E       sar     eax, 1E// 00401630  \.  C3            retn}int fn_div_2_31(int a) {    return a / 2147483648;// 00401640 >/$  8B4424 04     mov     eax, dword ptr [esp+4]// 00401644  |.  C1E8 1F       shr     eax, 1F// 00401647  \.  C3            retn}
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