1156cd587Sjoerg// This file is dual licensed under the MIT and the University of Illinois Open 2156cd587Sjoerg// Source Licenses. See LICENSE.TXT for details. 3156cd587Sjoerg 4156cd587Sjoerg#include "../assembly.h" 5156cd587Sjoerg 6156cd587Sjoerg// du_int __udivdi3(du_int a, du_int b); 7156cd587Sjoerg 8156cd587Sjoerg// result = a / b. 9156cd587Sjoerg// both inputs and the output are 64-bit unsigned integers. 10156cd587Sjoerg// This will do whatever the underlying hardware is set to do on division by zero. 11156cd587Sjoerg// No other exceptions are generated, as the divide cannot overflow. 12156cd587Sjoerg// 13156cd587Sjoerg// This is targeted at 32-bit x86 *only*, as this can be done directly in hardware 14156cd587Sjoerg// on x86_64. The performance goal is ~40 cycles per divide, which is faster than 15156cd587Sjoerg// currently possible via simulation of integer divides on the x87 unit. 16156cd587Sjoerg// 17156cd587Sjoerg// Stephen Canon, December 2008 18156cd587Sjoerg 19156cd587Sjoerg#ifdef __i386__ 20156cd587Sjoerg 21156cd587Sjoerg.text 22*61f2f256Sjoerg.balign 4 23156cd587SjoergDEFINE_COMPILERRT_FUNCTION(__udivdi3) 24156cd587Sjoerg 25156cd587Sjoerg pushl %ebx 26156cd587Sjoerg movl 20(%esp), %ebx // Find the index i of the leading bit in b. 27156cd587Sjoerg bsrl %ebx, %ecx // If the high word of b is zero, jump to 28156cd587Sjoerg jz 9f // the code to handle that special case [9]. 29156cd587Sjoerg 30156cd587Sjoerg /* High word of b is known to be non-zero on this branch */ 31156cd587Sjoerg 32156cd587Sjoerg movl 16(%esp), %eax // Construct bhi, containing bits [1+i:32+i] of b 33156cd587Sjoerg 34156cd587Sjoerg shrl %cl, %eax // Practically, this means that bhi is given by: 35156cd587Sjoerg shrl %eax // 36156cd587Sjoerg notl %ecx // bhi = (high word of b) << (31 - i) | 37156cd587Sjoerg shll %cl, %ebx // (low word of b) >> (1 + i) 38156cd587Sjoerg orl %eax, %ebx // 39156cd587Sjoerg movl 12(%esp), %edx // Load the high and low words of a, and jump 40156cd587Sjoerg movl 8(%esp), %eax // to [1] if the high word is larger than bhi 41156cd587Sjoerg cmpl %ebx, %edx // to avoid overflowing the upcoming divide. 42156cd587Sjoerg jae 1f 43156cd587Sjoerg 44156cd587Sjoerg /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */ 45156cd587Sjoerg 46156cd587Sjoerg divl %ebx // eax <-- qs, edx <-- r such that ahi:alo = bs*qs + r 47156cd587Sjoerg 48156cd587Sjoerg pushl %edi 49156cd587Sjoerg notl %ecx 50156cd587Sjoerg shrl %eax 51156cd587Sjoerg shrl %cl, %eax // q = qs >> (1 + i) 52156cd587Sjoerg movl %eax, %edi 53156cd587Sjoerg mull 20(%esp) // q*blo 54156cd587Sjoerg movl 12(%esp), %ebx 55156cd587Sjoerg movl 16(%esp), %ecx // ECX:EBX = a 56156cd587Sjoerg subl %eax, %ebx 57156cd587Sjoerg sbbl %edx, %ecx // ECX:EBX = a - q*blo 58156cd587Sjoerg movl 24(%esp), %eax 59156cd587Sjoerg imull %edi, %eax // q*bhi 60156cd587Sjoerg subl %eax, %ecx // ECX:EBX = a - q*b 61156cd587Sjoerg sbbl $0, %edi // decrement q if remainder is negative 62156cd587Sjoerg xorl %edx, %edx 63156cd587Sjoerg movl %edi, %eax 64156cd587Sjoerg popl %edi 65156cd587Sjoerg popl %ebx 66156cd587Sjoerg retl 67156cd587Sjoerg 68156cd587Sjoerg 69156cd587Sjoerg1: /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */ 70156cd587Sjoerg 71156cd587Sjoerg subl %ebx, %edx // subtract bhi from ahi so that divide will not 72156cd587Sjoerg divl %ebx // overflow, and find q and r such that 73156cd587Sjoerg // 74156cd587Sjoerg // ahi:alo = (1:q)*bhi + r 75156cd587Sjoerg // 76156cd587Sjoerg // Note that q is a number in (31-i).(1+i) 77156cd587Sjoerg // fix point. 78156cd587Sjoerg 79156cd587Sjoerg pushl %edi 80156cd587Sjoerg notl %ecx 81156cd587Sjoerg shrl %eax 82156cd587Sjoerg orl $0x80000000, %eax 83156cd587Sjoerg shrl %cl, %eax // q = (1:qs) >> (1 + i) 84156cd587Sjoerg movl %eax, %edi 85156cd587Sjoerg mull 20(%esp) // q*blo 86156cd587Sjoerg movl 12(%esp), %ebx 87156cd587Sjoerg movl 16(%esp), %ecx // ECX:EBX = a 88156cd587Sjoerg subl %eax, %ebx 89156cd587Sjoerg sbbl %edx, %ecx // ECX:EBX = a - q*blo 90156cd587Sjoerg movl 24(%esp), %eax 91156cd587Sjoerg imull %edi, %eax // q*bhi 92156cd587Sjoerg subl %eax, %ecx // ECX:EBX = a - q*b 93156cd587Sjoerg sbbl $0, %edi // decrement q if remainder is negative 94156cd587Sjoerg xorl %edx, %edx 95156cd587Sjoerg movl %edi, %eax 96156cd587Sjoerg popl %edi 97156cd587Sjoerg popl %ebx 98156cd587Sjoerg retl 99156cd587Sjoerg 100156cd587Sjoerg 101156cd587Sjoerg9: /* High word of b is zero on this branch */ 102156cd587Sjoerg 103156cd587Sjoerg movl 12(%esp), %eax // Find qhi and rhi such that 104156cd587Sjoerg movl 16(%esp), %ecx // 105156cd587Sjoerg xorl %edx, %edx // ahi = qhi*b + rhi with 0 ≤ rhi < b 106156cd587Sjoerg divl %ecx // 107156cd587Sjoerg movl %eax, %ebx // 108156cd587Sjoerg movl 8(%esp), %eax // Find qlo such that 109156cd587Sjoerg divl %ecx // 110156cd587Sjoerg movl %ebx, %edx // rhi:alo = qlo*b + rlo with 0 ≤ rlo < b 111156cd587Sjoerg popl %ebx // 112156cd587Sjoerg retl // and return qhi:qlo 113156cd587SjoergEND_COMPILERRT_FUNCTION(__udivdi3) 114156cd587Sjoerg 115156cd587Sjoerg#endif // __i386__ 116