diff options
Diffstat (limited to 'xorg-server/hw/xfree86/x86emu/prim_ops.c')
| -rw-r--r-- | xorg-server/hw/xfree86/x86emu/prim_ops.c | 70 |
1 files changed, 35 insertions, 35 deletions
diff --git a/xorg-server/hw/xfree86/x86emu/prim_ops.c b/xorg-server/hw/xfree86/x86emu/prim_ops.c index 24f76b47f..5604c7e81 100644 --- a/xorg-server/hw/xfree86/x86emu/prim_ops.c +++ b/xorg-server/hw/xfree86/x86emu/prim_ops.c @@ -883,9 +883,9 @@ rcl_byte(u8 d, u8 s) /* s is the rotate distance. It varies from 0 - 8. */ /* have - CF B_7 B_6 B_5 B_4 B_3 B_2 B_1 B_0 + CF B_7 B_6 B_5 B_4 B_3 B_2 B_1 B_0 - want to rotate through the carry by "s" bits. We could + want to rotate through the carry by "s" bits. We could loop, but that's inefficient. So the width is 9, and we split into three parts: @@ -895,12 +895,12 @@ rcl_byte(u8 d, u8 s) The new rotate is done mod 9, and given this, for a rotation of n bits (mod 9) the new carry flag is - then located n bits from the MSB. The low part is + then located n bits from the MSB. The low part is then shifted up cnt bits, and the high part is or'd - in. Using CAPS for new values, and lowercase for the + in. Using CAPS for new values, and lowercase for the original values, this can be expressed as: - IF n > 0 + IF n > 0 1) CF <- b_(8-n) 2) B_(7) .. B_(n) <- b_(8-(n+1)) .. b_0 3) B_(n-1) <- cf @@ -912,17 +912,17 @@ rcl_byte(u8 d, u8 s) /* CF <- b_(8-n) */ cf = (d >> (8 - cnt)) & 0x1; - /* get the low stuff which rotated + /* get the low stuff which rotated into the range B_7 .. B_cnt */ /* B_(7) .. B_(n) <- b_(8-(n+1)) .. b_0 */ /* note that the right hand side done by the mask */ res = (d << cnt) & 0xff; - /* now the high stuff which rotated around + /* now the high stuff which rotated around into the positions B_cnt-2 .. B_0 */ /* B_(n-2) .. B_0 <- b_7 .. b_(8-(n-1)) */ - /* shift it downward, 7-(n-2) = 9-n positions. - and mask off the result before or'ing in. + /* shift it downward, 7-(n-2) = 9-n positions. + and mask off the result before or'ing in. */ mask = (1 << (cnt - 1)) - 1; res |= (d >> (9 - cnt)) & mask; @@ -934,7 +934,7 @@ rcl_byte(u8 d, u8 s) } /* set the new carry flag, based on the variable "cf" */ CONDITIONAL_SET_FLAG(cf, F_CF); - /* OVERFLOW is set *IFF* cnt==1, then it is the + /* OVERFLOW is set *IFF* cnt==1, then it is the xor of CF and the most significant bit. Blecck. */ /* parenthesized this expression since it appears to be causing OF to be misset */ @@ -1003,22 +1003,22 @@ rcr_byte(u8 d, u8 s) u32 mask, cf, ocf = 0; /* rotate right through carry */ - /* + /* s is the rotate distance. It varies from 0 - 8. - d is the byte object rotated. + d is the byte object rotated. - have + have - CF B_7 B_6 B_5 B_4 B_3 B_2 B_1 B_0 + CF B_7 B_6 B_5 B_4 B_3 B_2 B_1 B_0 The new rotate is done mod 9, and given this, for a rotation of n bits (mod 9) the new carry flag is - then located n bits from the LSB. The low part is + then located n bits from the LSB. The low part is then shifted up cnt bits, and the high part is or'd - in. Using CAPS for new values, and lowercase for the + in. Using CAPS for new values, and lowercase for the original values, this can be expressed as: - IF n > 0 + IF n > 0 1) CF <- b_(n-1) 2) B_(8-(n+1)) .. B_(0) <- b_(7) .. b_(n) 3) B_(8-n) <- cf @@ -1033,7 +1033,7 @@ rcr_byte(u8 d, u8 s) /* note hackery here. Access_flag(..) evaluates to either 0 if flag not set non-zero if flag is set. - doing access_flag(..) != 0 casts that into either + doing access_flag(..) != 0 casts that into either 0..1 in any representation of the flags register (i.e. packed bit array or unpacked.) */ @@ -1044,19 +1044,19 @@ rcr_byte(u8 d, u8 s) /* B_(8-(n+1)) .. B_(0) <- b_(7) .. b_n */ /* note that the right hand side done by the mask - This is effectively done by shifting the + This is effectively done by shifting the object to the right. The result must be masked, - in case the object came in and was treated + in case the object came in and was treated as a negative number. Needed??? */ mask = (1 << (8 - cnt)) - 1; res = (d >> cnt) & mask; - /* now the high stuff which rotated around + /* now the high stuff which rotated around into the positions B_cnt-2 .. B_0 */ /* B_(7) .. B_(8-(n-1)) <- b_(n-2) .. b_(0) */ - /* shift it downward, 7-(n-2) = 9-n positions. - and mask off the result before or'ing in. + /* shift it downward, 7-(n-2) = 9-n positions. + and mask off the result before or'ing in. */ res |= (d << (9 - cnt)); @@ -1067,7 +1067,7 @@ rcr_byte(u8 d, u8 s) } /* set the new carry flag, based on the variable "cf" */ CONDITIONAL_SET_FLAG(cf, F_CF); - /* OVERFLOW is set *IFF* cnt==1, then it is the + /* OVERFLOW is set *IFF* cnt==1, then it is the xor of CF and the most significant bit. Blecck. */ /* parenthesized... */ if (cnt == 1) { @@ -1154,18 +1154,18 @@ rol_byte(u8 d, u8 s) register unsigned int res, cnt, mask; /* rotate left */ - /* + /* s is the rotate distance. It varies from 0 - 8. - d is the byte object rotated. + d is the byte object rotated. - have + have - CF B_7 ... B_0 + CF B_7 ... B_0 The new rotate is done mod 8. Much simpler than the "rcl" or "rcr" operations. - IF n > 0 + IF n > 0 1) B_(7) .. B_(n) <- b_(8-(n+1)) .. b_(0) 2) B_(n-1) .. B_(0) <- b_(7) .. b_(8-n) */ @@ -1256,17 +1256,17 @@ ror_byte(u8 d, u8 s) register unsigned int res, cnt, mask; /* rotate right */ - /* + /* s is the rotate distance. It varies from 0 - 8. - d is the byte object rotated. + d is the byte object rotated. - have + have - B_7 ... B_0 + B_7 ... B_0 The rotate is done mod 8. - IF n > 0 + IF n > 0 1) B_(8-(n+1)) .. B_(0) <- b_(7) .. b_(n) 2) B_(7) .. B_(8-n) <- b_(n-1) .. b_(0) */ @@ -1279,7 +1279,7 @@ ror_byte(u8 d, u8 s) mask = (1 << (8 - cnt)) - 1; res |= (d >> (cnt)) & mask; - /* set the new carry flag, Note that it is the low order + /* set the new carry flag, Note that it is the low order bit of the result!!! */ CONDITIONAL_SET_FLAG(res & 0x80, F_CF); /* OVERFLOW is set *IFF* s==1, then it is the |