1353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 2353358Sdim// See https://llvm.org/LICENSE.txt for license information. 3353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 4276789Sdim 5276789Sdim#include "../assembly.h" 6276789Sdim 7276789Sdim// di_int __moddi3(di_int a, di_int b); 8276789Sdim 9276789Sdim// result = remainder of a / b. 10276789Sdim// both inputs and the output are 64-bit signed integers. 11276789Sdim// This will do whatever the underlying hardware is set to do on division by zero. 12276789Sdim// No other exceptions are generated, as the divide cannot overflow. 13276789Sdim// 14276789Sdim// This is targeted at 32-bit x86 *only*, as this can be done directly in hardware 15276789Sdim// on x86_64. The performance goal is ~40 cycles per divide, which is faster than 16276789Sdim// currently possible via simulation of integer divides on the x87 unit. 17276789Sdim// 18276789Sdim 19276789Sdim// Stephen Canon, December 2008 20276789Sdim 21276789Sdim#ifdef __i386__ 22276789Sdim 23276789Sdim.text 24276789Sdim.balign 4 25276789SdimDEFINE_COMPILERRT_FUNCTION(__moddi3) 26276789Sdim 27353358Sdim// This is currently implemented by wrapping the unsigned modulus up in an absolute 28353358Sdim// value. This could certainly be improved upon. 29276789Sdim 30276789Sdim pushl %esi 31276789Sdim movl 20(%esp), %edx // high word of b 32276789Sdim movl 16(%esp), %eax // low word of b 33276789Sdim movl %edx, %ecx 34276789Sdim sarl $31, %ecx // (b < 0) ? -1 : 0 35276789Sdim xorl %ecx, %eax 36276789Sdim xorl %ecx, %edx // EDX:EAX = (b < 0) ? not(b) : b 37276789Sdim subl %ecx, %eax 38276789Sdim sbbl %ecx, %edx // EDX:EAX = abs(b) 39276789Sdim movl %edx, 20(%esp) 40276789Sdim movl %eax, 16(%esp) // store abs(b) back to stack 41353358Sdim 42276789Sdim movl 12(%esp), %edx // high word of b 43276789Sdim movl 8(%esp), %eax // low word of b 44276789Sdim movl %edx, %ecx 45276789Sdim sarl $31, %ecx // (a < 0) ? -1 : 0 46276789Sdim xorl %ecx, %eax 47276789Sdim xorl %ecx, %edx // EDX:EAX = (a < 0) ? not(a) : a 48276789Sdim subl %ecx, %eax 49276789Sdim sbbl %ecx, %edx // EDX:EAX = abs(a) 50276789Sdim movl %edx, 12(%esp) 51276789Sdim movl %eax, 8(%esp) // store abs(a) back to stack 52276789Sdim movl %ecx, %esi // set aside sign of a 53276789Sdim 54276789Sdim pushl %ebx 55276789Sdim movl 24(%esp), %ebx // Find the index i of the leading bit in b. 56276789Sdim bsrl %ebx, %ecx // If the high word of b is zero, jump to 57276789Sdim jz 9f // the code to handle that special case [9]. 58353358Sdim 59353358Sdim // High word of b is known to be non-zero on this branch 60353358Sdim 61276789Sdim movl 20(%esp), %eax // Construct bhi, containing bits [1+i:32+i] of b 62353358Sdim 63276789Sdim shrl %cl, %eax // Practically, this means that bhi is given by: 64276789Sdim shrl %eax // 65276789Sdim notl %ecx // bhi = (high word of b) << (31 - i) | 66276789Sdim shll %cl, %ebx // (low word of b) >> (1 + i) 67276789Sdim orl %eax, %ebx // 68276789Sdim movl 16(%esp), %edx // Load the high and low words of a, and jump 69276789Sdim movl 12(%esp), %eax // to [2] if the high word is larger than bhi 70276789Sdim cmpl %ebx, %edx // to avoid overflowing the upcoming divide. 71353358Sdim jae 2f 72353358Sdim 73353358Sdim // High word of a is greater than or equal to (b >> (1 + i)) on this branch 74353358Sdim 75276789Sdim divl %ebx // eax <-- qs, edx <-- r such that ahi:alo = bs*qs + r 76276789Sdim 77276789Sdim pushl %edi 78276789Sdim notl %ecx 79276789Sdim shrl %eax 80276789Sdim shrl %cl, %eax // q = qs >> (1 + i) 81276789Sdim movl %eax, %edi 82276789Sdim mull 24(%esp) // q*blo 83276789Sdim movl 16(%esp), %ebx 84276789Sdim movl 20(%esp), %ecx // ECX:EBX = a 85276789Sdim subl %eax, %ebx 86276789Sdim sbbl %edx, %ecx // ECX:EBX = a - q*blo 87276789Sdim movl 28(%esp), %eax 88276789Sdim imull %edi, %eax // q*bhi 89276789Sdim subl %eax, %ecx // ECX:EBX = a - q*b 90353358Sdim 91276789Sdim jnc 1f // if positive, this is the result. 92276789Sdim addl 24(%esp), %ebx // otherwise 93276789Sdim adcl 28(%esp), %ecx // ECX:EBX = a - (q-1)*b = result 94276789Sdim1: movl %ebx, %eax 95276789Sdim movl %ecx, %edx 96353358Sdim 97276789Sdim addl %esi, %eax // Restore correct sign to result 98276789Sdim adcl %esi, %edx 99276789Sdim xorl %esi, %eax 100276789Sdim xorl %esi, %edx 101276789Sdim popl %edi // Restore callee-save registers 102276789Sdim popl %ebx 103276789Sdim popl %esi 104276789Sdim retl // Return 105276789Sdim 106353358Sdim2: // High word of a is greater than or equal to (b >> (1 + i)) on this branch 107353358Sdim 108276789Sdim subl %ebx, %edx // subtract bhi from ahi so that divide will not 109276789Sdim divl %ebx // overflow, and find q and r such that 110276789Sdim // 111276789Sdim // ahi:alo = (1:q)*bhi + r 112276789Sdim // 113276789Sdim // Note that q is a number in (31-i).(1+i) 114276789Sdim // fix point. 115276789Sdim 116276789Sdim pushl %edi 117276789Sdim notl %ecx 118276789Sdim shrl %eax 119276789Sdim orl $0x80000000, %eax 120276789Sdim shrl %cl, %eax // q = (1:qs) >> (1 + i) 121276789Sdim movl %eax, %edi 122276789Sdim mull 24(%esp) // q*blo 123276789Sdim movl 16(%esp), %ebx 124276789Sdim movl 20(%esp), %ecx // ECX:EBX = a 125276789Sdim subl %eax, %ebx 126276789Sdim sbbl %edx, %ecx // ECX:EBX = a - q*blo 127276789Sdim movl 28(%esp), %eax 128276789Sdim imull %edi, %eax // q*bhi 129276789Sdim subl %eax, %ecx // ECX:EBX = a - q*b 130276789Sdim 131276789Sdim jnc 3f // if positive, this is the result. 132276789Sdim addl 24(%esp), %ebx // otherwise 133276789Sdim adcl 28(%esp), %ecx // ECX:EBX = a - (q-1)*b = result 134276789Sdim3: movl %ebx, %eax 135276789Sdim movl %ecx, %edx 136353358Sdim 137276789Sdim addl %esi, %eax // Restore correct sign to result 138276789Sdim adcl %esi, %edx 139276789Sdim xorl %esi, %eax 140276789Sdim xorl %esi, %edx 141276789Sdim popl %edi // Restore callee-save registers 142276789Sdim popl %ebx 143276789Sdim popl %esi 144276789Sdim retl // Return 145276789Sdim 146353358Sdim9: // High word of b is zero on this branch 147353358Sdim 148276789Sdim movl 16(%esp), %eax // Find qhi and rhi such that 149276789Sdim movl 20(%esp), %ecx // 150276789Sdim xorl %edx, %edx // ahi = qhi*b + rhi with 0 ��� rhi < b 151276789Sdim divl %ecx // 152276789Sdim movl %eax, %ebx // 153276789Sdim movl 12(%esp), %eax // Find rlo such that 154276789Sdim divl %ecx // 155276789Sdim movl %edx, %eax // rhi:alo = qlo*b + rlo with 0 ��� rlo < b 156276789Sdim popl %ebx // 157276789Sdim xorl %edx, %edx // and return 0:rlo 158276789Sdim 159276789Sdim addl %esi, %eax // Restore correct sign to result 160276789Sdim adcl %esi, %edx 161276789Sdim xorl %esi, %eax 162276789Sdim xorl %esi, %edx 163276789Sdim popl %esi 164276789Sdim retl // Return 165276789SdimEND_COMPILERRT_FUNCTION(__moddi3) 166276789Sdim 167276789Sdim#endif // __i386__ 168309124Sdim 169309124SdimNO_EXEC_STACK_DIRECTIVE 170309124Sdim 171