diff options
Diffstat (limited to 'lib/builtins/i386/divdi3.S')
| -rw-r--r-- | lib/builtins/i386/divdi3.S | 43 |
1 files changed, 22 insertions, 21 deletions
diff --git a/lib/builtins/i386/divdi3.S b/lib/builtins/i386/divdi3.S index 2fb4bdcad90d..09e1e42eb719 100644 --- a/lib/builtins/i386/divdi3.S +++ b/lib/builtins/i386/divdi3.S @@ -1,5 +1,6 @@ -// This file is dual licensed under the MIT and the University of Illinois Open -// Source Licenses. See LICENSE.TXT for details. +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception #include "../assembly.h" @@ -22,9 +23,9 @@ .balign 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. */ +// 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 @@ -38,7 +39,7 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 @@ -55,11 +56,11 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 */ - + + // 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) | @@ -68,10 +69,10 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 */ - + 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 @@ -90,7 +91,7 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 @@ -101,8 +102,8 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) retl // Return -1: /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */ - +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 // @@ -128,7 +129,7 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 @@ -138,8 +139,8 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) popl %esi retl // Return - -9: /* High word of b is zero on this branch */ + +9: // High word of b is zero on this branch movl 16(%esp), %eax // Find qhi and rhi such that movl 20(%esp), %ecx // @@ -149,7 +150,7 @@ DEFINE_COMPILERRT_FUNCTION(__divdi3) 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 |