1222656Sed// This file is dual licensed under the MIT and the University of Illinois Open 2222656Sed// Source Licenses. See LICENSE.TXT for details. 3214152Sed 4214152Sed#include "../assembly.h" 5214152Sed 6214152Sed// du_int __umoddi3(du_int a, du_int b); 7214152Sed 8214152Sed// result = remainder of a / b. 9214152Sed// both inputs and the output are 64-bit unsigned integers. 10214152Sed// This will do whatever the underlying hardware is set to do on division by zero. 11214152Sed// No other exceptions are generated, as the divide cannot overflow. 12214152Sed// 13214152Sed// This is targeted at 32-bit x86 *only*, as this can be done directly in hardware 14214152Sed// on x86_64. The performance goal is ~40 cycles per divide, which is faster than 15214152Sed// currently possible via simulation of integer divides on the x87 unit. 16214152Sed// 17214152Sed 18214152Sed// Stephen Canon, December 2008 19214152Sed 20214152Sed#ifdef __i386__ 21214152Sed 22214152Sed.text 23214152Sed.align 4 24214152SedDEFINE_COMPILERRT_FUNCTION(__umoddi3) 25214152Sed 26214152Sed pushl %ebx 27214152Sed movl 20(%esp), %ebx // Find the index i of the leading bit in b. 28214152Sed bsrl %ebx, %ecx // If the high word of b is zero, jump to 29214152Sed jz 9f // the code to handle that special case [9]. 30214152Sed 31214152Sed /* High word of b is known to be non-zero on this branch */ 32214152Sed 33214152Sed movl 16(%esp), %eax // Construct bhi, containing bits [1+i:32+i] of b 34214152Sed 35214152Sed shrl %cl, %eax // Practically, this means that bhi is given by: 36214152Sed shrl %eax // 37214152Sed notl %ecx // bhi = (high word of b) << (31 - i) | 38214152Sed shll %cl, %ebx // (low word of b) >> (1 + i) 39214152Sed orl %eax, %ebx // 40214152Sed movl 12(%esp), %edx // Load the high and low words of a, and jump 41214152Sed movl 8(%esp), %eax // to [2] if the high word is larger than bhi 42214152Sed cmpl %ebx, %edx // to avoid overflowing the upcoming divide. 43214152Sed jae 2f 44214152Sed 45214152Sed /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */ 46214152Sed 47214152Sed divl %ebx // eax <-- qs, edx <-- r such that ahi:alo = bs*qs + r 48214152Sed 49214152Sed pushl %edi 50214152Sed notl %ecx 51214152Sed shrl %eax 52214152Sed shrl %cl, %eax // q = qs >> (1 + i) 53214152Sed movl %eax, %edi 54214152Sed mull 20(%esp) // q*blo 55214152Sed movl 12(%esp), %ebx 56214152Sed movl 16(%esp), %ecx // ECX:EBX = a 57214152Sed subl %eax, %ebx 58214152Sed sbbl %edx, %ecx // ECX:EBX = a - q*blo 59214152Sed movl 24(%esp), %eax 60214152Sed imull %edi, %eax // q*bhi 61214152Sed subl %eax, %ecx // ECX:EBX = a - q*b 62214152Sed 63214152Sed jnc 1f // if positive, this is the result. 64214152Sed addl 20(%esp), %ebx // otherwise 65214152Sed adcl 24(%esp), %ecx // ECX:EBX = a - (q-1)*b = result 66214152Sed1: movl %ebx, %eax 67214152Sed movl %ecx, %edx 68214152Sed 69214152Sed popl %edi 70214152Sed popl %ebx 71214152Sed retl 72214152Sed 73214152Sed 74214152Sed2: /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */ 75214152Sed 76214152Sed subl %ebx, %edx // subtract bhi from ahi so that divide will not 77214152Sed divl %ebx // overflow, and find q and r such that 78214152Sed // 79214152Sed // ahi:alo = (1:q)*bhi + r 80214152Sed // 81214152Sed // Note that q is a number in (31-i).(1+i) 82214152Sed // fix point. 83214152Sed 84214152Sed pushl %edi 85214152Sed notl %ecx 86214152Sed shrl %eax 87214152Sed orl $0x80000000, %eax 88214152Sed shrl %cl, %eax // q = (1:qs) >> (1 + i) 89214152Sed movl %eax, %edi 90214152Sed mull 20(%esp) // q*blo 91214152Sed movl 12(%esp), %ebx 92214152Sed movl 16(%esp), %ecx // ECX:EBX = a 93214152Sed subl %eax, %ebx 94214152Sed sbbl %edx, %ecx // ECX:EBX = a - q*blo 95214152Sed movl 24(%esp), %eax 96214152Sed imull %edi, %eax // q*bhi 97214152Sed subl %eax, %ecx // ECX:EBX = a - q*b 98214152Sed 99214152Sed jnc 3f // if positive, this is the result. 100214152Sed addl 20(%esp), %ebx // otherwise 101214152Sed adcl 24(%esp), %ecx // ECX:EBX = a - (q-1)*b = result 102214152Sed3: movl %ebx, %eax 103214152Sed movl %ecx, %edx 104214152Sed 105214152Sed popl %edi 106214152Sed popl %ebx 107214152Sed retl 108214152Sed 109214152Sed 110214152Sed 111214152Sed9: /* High word of b is zero on this branch */ 112214152Sed 113214152Sed movl 12(%esp), %eax // Find qhi and rhi such that 114214152Sed movl 16(%esp), %ecx // 115214152Sed xorl %edx, %edx // ahi = qhi*b + rhi with 0 ��� rhi < b 116214152Sed divl %ecx // 117214152Sed movl %eax, %ebx // 118214152Sed movl 8(%esp), %eax // Find rlo such that 119214152Sed divl %ecx // 120214152Sed movl %edx, %eax // rhi:alo = qlo*b + rlo with 0 ��� rlo < b 121214152Sed popl %ebx // 122214152Sed xorl %edx, %edx // and return 0:rlo 123214152Sed retl // 124214152Sed 125214152Sed#endif // __i386__ 126