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Diffstat (limited to 'lib/i386/divdi3.S')
| -rw-r--r-- | lib/i386/divdi3.S | 161 |
1 files changed, 0 insertions, 161 deletions
diff --git a/lib/i386/divdi3.S b/lib/i386/divdi3.S deleted file mode 100644 index 69593e32e9e39..0000000000000 --- a/lib/i386/divdi3.S +++ /dev/null @@ -1,161 +0,0 @@ -// 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__ |