forked from OSchip/llvm-project
162 lines
4.9 KiB
ArmAsm
162 lines
4.9 KiB
ArmAsm
// This file is dual licensed under the MIT and the University of Illinois Open
|
|
// Source Licenses. See LICENSE.TXT for details.
|
|
|
|
#include "../assembly.h"
|
|
|
|
// di_int __divdi3(di_int a, di_int b);
|
|
|
|
// result = a / b.
|
|
// both inputs and the output are 64-bit signed integers.
|
|
// This will do whatever the underlying hardware is set to do on division by zero.
|
|
// No other exceptions are generated, as the divide cannot overflow.
|
|
//
|
|
// This is targeted at 32-bit x86 *only*, as this can be done directly in hardware
|
|
// on x86_64. The performance goal is ~40 cycles per divide, which is faster than
|
|
// currently possible via simulation of integer divides on the x87 unit.
|
|
//
|
|
// Stephen Canon, December 2008
|
|
|
|
#ifdef __i386__
|
|
|
|
.text
|
|
.align 4
|
|
DEFINE_COMPILERRT_FUNCTION(__divdi3)
|
|
|
|
/* This is currently implemented by wrapping the unsigned divide up in an absolute
|
|
value, then restoring the correct sign at the end of the computation. This could
|
|
certainly be improved upon. */
|
|
|
|
pushl %esi
|
|
movl 20(%esp), %edx // high word of b
|
|
movl 16(%esp), %eax // low word of b
|
|
movl %edx, %ecx
|
|
sarl $31, %ecx // (b < 0) ? -1 : 0
|
|
xorl %ecx, %eax
|
|
xorl %ecx, %edx // EDX:EAX = (b < 0) ? not(b) : b
|
|
subl %ecx, %eax
|
|
sbbl %ecx, %edx // EDX:EAX = abs(b)
|
|
movl %edx, 20(%esp)
|
|
movl %eax, 16(%esp) // store abs(b) back to stack
|
|
movl %ecx, %esi // set aside sign of b
|
|
|
|
movl 12(%esp), %edx // high word of b
|
|
movl 8(%esp), %eax // low word of b
|
|
movl %edx, %ecx
|
|
sarl $31, %ecx // (a < 0) ? -1 : 0
|
|
xorl %ecx, %eax
|
|
xorl %ecx, %edx // EDX:EAX = (a < 0) ? not(a) : a
|
|
subl %ecx, %eax
|
|
sbbl %ecx, %edx // EDX:EAX = abs(a)
|
|
movl %edx, 12(%esp)
|
|
movl %eax, 8(%esp) // store abs(a) back to stack
|
|
xorl %ecx, %esi // sign of result = (sign of a) ^ (sign of b)
|
|
|
|
pushl %ebx
|
|
movl 24(%esp), %ebx // Find the index i of the leading bit in b.
|
|
bsrl %ebx, %ecx // If the high word of b is zero, jump to
|
|
jz 9f // the code to handle that special case [9].
|
|
|
|
/* High word of b is known to be non-zero on this branch */
|
|
|
|
movl 20(%esp), %eax // Construct bhi, containing bits [1+i:32+i] of b
|
|
|
|
shrl %cl, %eax // Practically, this means that bhi is given by:
|
|
shrl %eax //
|
|
notl %ecx // bhi = (high word of b) << (31 - i) |
|
|
shll %cl, %ebx // (low word of b) >> (1 + i)
|
|
orl %eax, %ebx //
|
|
movl 16(%esp), %edx // Load the high and low words of a, and jump
|
|
movl 12(%esp), %eax // to [1] if the high word is larger than bhi
|
|
cmpl %ebx, %edx // to avoid overflowing the upcoming divide.
|
|
jae 1f
|
|
|
|
/* High word of a is greater than or equal to (b >> (1 + i)) on this branch */
|
|
|
|
divl %ebx // eax <-- qs, edx <-- r such that ahi:alo = bs*qs + r
|
|
|
|
pushl %edi
|
|
notl %ecx
|
|
shrl %eax
|
|
shrl %cl, %eax // q = qs >> (1 + i)
|
|
movl %eax, %edi
|
|
mull 24(%esp) // q*blo
|
|
movl 16(%esp), %ebx
|
|
movl 20(%esp), %ecx // ECX:EBX = a
|
|
subl %eax, %ebx
|
|
sbbl %edx, %ecx // ECX:EBX = a - q*blo
|
|
movl 28(%esp), %eax
|
|
imull %edi, %eax // q*bhi
|
|
subl %eax, %ecx // ECX:EBX = a - q*b
|
|
sbbl $0, %edi // decrement q if remainder is negative
|
|
xorl %edx, %edx
|
|
movl %edi, %eax
|
|
|
|
addl %esi, %eax // Restore correct sign to result
|
|
adcl %esi, %edx
|
|
xorl %esi, %eax
|
|
xorl %esi, %edx
|
|
popl %edi // Restore callee-save registers
|
|
popl %ebx
|
|
popl %esi
|
|
retl // Return
|
|
|
|
|
|
1: /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */
|
|
|
|
subl %ebx, %edx // subtract bhi from ahi so that divide will not
|
|
divl %ebx // overflow, and find q and r such that
|
|
//
|
|
// ahi:alo = (1:q)*bhi + r
|
|
//
|
|
// Note that q is a number in (31-i).(1+i)
|
|
// fix point.
|
|
|
|
pushl %edi
|
|
notl %ecx
|
|
shrl %eax
|
|
orl $0x80000000, %eax
|
|
shrl %cl, %eax // q = (1:qs) >> (1 + i)
|
|
movl %eax, %edi
|
|
mull 24(%esp) // q*blo
|
|
movl 16(%esp), %ebx
|
|
movl 20(%esp), %ecx // ECX:EBX = a
|
|
subl %eax, %ebx
|
|
sbbl %edx, %ecx // ECX:EBX = a - q*blo
|
|
movl 28(%esp), %eax
|
|
imull %edi, %eax // q*bhi
|
|
subl %eax, %ecx // ECX:EBX = a - q*b
|
|
sbbl $0, %edi // decrement q if remainder is negative
|
|
xorl %edx, %edx
|
|
movl %edi, %eax
|
|
|
|
addl %esi, %eax // Restore correct sign to result
|
|
adcl %esi, %edx
|
|
xorl %esi, %eax
|
|
xorl %esi, %edx
|
|
popl %edi // Restore callee-save registers
|
|
popl %ebx
|
|
popl %esi
|
|
retl // Return
|
|
|
|
|
|
9: /* High word of b is zero on this branch */
|
|
|
|
movl 16(%esp), %eax // Find qhi and rhi such that
|
|
movl 20(%esp), %ecx //
|
|
xorl %edx, %edx // ahi = qhi*b + rhi with 0 ≤ rhi < b
|
|
divl %ecx //
|
|
movl %eax, %ebx //
|
|
movl 12(%esp), %eax // Find qlo such that
|
|
divl %ecx //
|
|
movl %ebx, %edx // rhi:alo = qlo*b + rlo with 0 ≤ rlo < b
|
|
|
|
addl %esi, %eax // Restore correct sign to result
|
|
adcl %esi, %edx
|
|
xorl %esi, %eax
|
|
xorl %esi, %edx
|
|
popl %ebx // Restore callee-save registers
|
|
popl %esi
|
|
retl // Return
|
|
|
|
#endif // __i386__
|