| /* Copyright (C) 2004-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "div_libc.h" |
| |
| |
| /* 64-bit signed long remainder. These are not normal C functions. Argument |
| registers are t10 and t11, the result goes in t12. Only t12 and AT may |
| be clobbered. |
| |
| Theory of operation here is that we can use the FPU divider for virtually |
| all operands that we see: all dividend values between -2**53 and 2**53-1 |
| can be computed directly. Note that divisor values need not be checked |
| against that range because the rounded fp value will be close enough such |
| that the quotient is < 1, which will properly be truncated to zero when we |
| convert back to integer. |
| |
| When the dividend is outside the range for which we can compute exact |
| results, we use the fp quotent as an estimate from which we begin refining |
| an exact integral value. This reduces the number of iterations in the |
| shift-and-subtract loop significantly. |
| |
| The FPCR save/restore is due to the fact that the EV6 _will_ set FPCR_INE |
| for cvttq/c even without /sui being set. It will not, however, properly |
| raise the exception, so we don't have to worry about FPCR_INED being clear |
| and so dying by SIGFPE. */ |
| |
| .text |
| .align 4 |
| .globl __remq |
| .type __remq, @funcnoplt |
| .usepv __remq, no |
| |
| cfi_startproc |
| cfi_return_column (RA) |
| __remq: |
| lda sp, -FRAME(sp) |
| cfi_def_cfa_offset (FRAME) |
| CALL_MCOUNT |
| |
| /* Get the fp divide insn issued as quickly as possible. After |
| that's done, we have at least 22 cycles until its results are |
| ready -- all the time in the world to figure out how we're |
| going to use the results. */ |
| stt $f0, 0(sp) |
| excb |
| beq Y, DIVBYZERO |
| |
| stt $f1, 8(sp) |
| stt $f3, 48(sp) |
| cfi_rel_offset ($f0, 0) |
| cfi_rel_offset ($f1, 8) |
| cfi_rel_offset ($f3, 48) |
| mf_fpcr $f3 |
| |
| _ITOFT2 X, $f0, 16, Y, $f1, 24 |
| cvtqt $f0, $f0 |
| cvtqt $f1, $f1 |
| divt/c $f0, $f1, $f0 |
| |
| /* Check to see if X fit in the double as an exact value. */ |
| sll X, (64-53), AT |
| ldt $f1, 8(sp) |
| sra AT, (64-53), AT |
| cmpeq X, AT, AT |
| beq AT, $x_big |
| |
| /* If we get here, we're expecting exact results from the division. |
| Do nothing else besides convert, compute remainder, clean up. */ |
| cvttq/c $f0, $f0 |
| excb |
| mt_fpcr $f3 |
| _FTOIT $f0, AT, 16 |
| mulq AT, Y, AT |
| ldt $f0, 0(sp) |
| ldt $f3, 48(sp) |
| cfi_restore ($f1) |
| cfi_remember_state |
| cfi_restore ($f0) |
| cfi_restore ($f3) |
| cfi_def_cfa_offset (0) |
| lda sp, FRAME(sp) |
| subq X, AT, RV |
| ret $31, (RA), 1 |
| |
| .align 4 |
| cfi_restore_state |
| $x_big: |
| /* If we get here, X is large enough that we don't expect exact |
| results, and neither X nor Y got mis-translated for the fp |
| division. Our task is to take the fp result, figure out how |
| far it's off from the correct result and compute a fixup. */ |
| stq t0, 16(sp) |
| stq t1, 24(sp) |
| stq t2, 32(sp) |
| stq t5, 40(sp) |
| cfi_rel_offset (t0, 16) |
| cfi_rel_offset (t1, 24) |
| cfi_rel_offset (t2, 32) |
| cfi_rel_offset (t5, 40) |
| |
| #define Q t0 /* quotient */ |
| #define R RV /* remainder */ |
| #define SY t1 /* scaled Y */ |
| #define S t2 /* scalar */ |
| #define QY t3 /* Q*Y */ |
| |
| /* The fixup code below can only handle unsigned values. */ |
| or X, Y, AT |
| mov $31, t5 |
| blt AT, $fix_sign_in |
| $fix_sign_in_ret1: |
| cvttq/c $f0, $f0 |
| |
| _FTOIT $f0, Q, 8 |
| .align 3 |
| $fix_sign_in_ret2: |
| ldt $f0, 0(sp) |
| stq t3, 0(sp) |
| cfi_restore ($f0) |
| cfi_rel_offset (t3, 0) |
| |
| mulq Q, Y, QY |
| excb |
| stq t4, 8(sp) |
| mt_fpcr $f3 |
| cfi_rel_offset (t4, 8) |
| |
| subq QY, X, R |
| mov Y, SY |
| mov 1, S |
| bgt R, $q_high |
| |
| $q_high_ret: |
| subq X, QY, R |
| mov Y, SY |
| mov 1, S |
| bgt R, $q_low |
| |
| $q_low_ret: |
| ldq t0, 16(sp) |
| ldq t1, 24(sp) |
| ldq t2, 32(sp) |
| bne t5, $fix_sign_out |
| |
| $fix_sign_out_ret: |
| ldq t3, 0(sp) |
| ldq t4, 8(sp) |
| ldq t5, 40(sp) |
| ldt $f3, 48(sp) |
| lda sp, FRAME(sp) |
| cfi_remember_state |
| cfi_restore (t0) |
| cfi_restore (t1) |
| cfi_restore (t2) |
| cfi_restore (t3) |
| cfi_restore (t4) |
| cfi_restore (t5) |
| cfi_restore ($f3) |
| cfi_def_cfa_offset (0) |
| ret $31, (RA), 1 |
| |
| .align 4 |
| cfi_restore_state |
| /* The quotient that we computed was too large. We need to reduce |
| it by S such that Y*S >= R. Obviously the closer we get to the |
| correct value the better, but overshooting high is ok, as we'll |
| fix that up later. */ |
| 0: |
| addq SY, SY, SY |
| addq S, S, S |
| $q_high: |
| cmpult SY, R, AT |
| bne AT, 0b |
| |
| subq Q, S, Q |
| unop |
| subq QY, SY, QY |
| br $q_high_ret |
| |
| .align 4 |
| /* The quotient that we computed was too small. Divide Y by the |
| current remainder (R) and add that to the existing quotient (Q). |
| The expectation, of course, is that R is much smaller than X. */ |
| /* Begin with a shift-up loop. Compute S such that Y*S >= R. We |
| already have a copy of Y in SY and the value 1 in S. */ |
| 0: |
| addq SY, SY, SY |
| addq S, S, S |
| $q_low: |
| cmpult SY, R, AT |
| bne AT, 0b |
| |
| /* Shift-down and subtract loop. Each iteration compares our scaled |
| Y (SY) with the remainder (R); if SY <= R then X is divisible by |
| Y's scalar (S) so add it to the quotient (Q). */ |
| 2: addq Q, S, t3 |
| srl S, 1, S |
| cmpule SY, R, AT |
| subq R, SY, t4 |
| |
| cmovne AT, t3, Q |
| cmovne AT, t4, R |
| srl SY, 1, SY |
| bne S, 2b |
| |
| br $q_low_ret |
| |
| .align 4 |
| $fix_sign_in: |
| /* If we got here, then X|Y is negative. Need to adjust everything |
| such that we're doing unsigned division in the fixup loop. */ |
| /* T5 records the changes we had to make: |
| bit 0: set if X was negated. Note that the sign of the |
| remainder follows the sign of the divisor. |
| bit 2: set if Y was negated. |
| */ |
| xor X, Y, t1 |
| cmplt X, 0, t5 |
| negq X, t0 |
| cmovne t5, t0, X |
| |
| cmplt Y, 0, AT |
| negq Y, t0 |
| s4addq AT, t5, t5 |
| cmovne AT, t0, Y |
| |
| bge t1, $fix_sign_in_ret1 |
| cvttq/c $f0, $f0 |
| _FTOIT $f0, Q, 8 |
| .align 3 |
| negq Q, Q |
| br $fix_sign_in_ret2 |
| |
| .align 4 |
| $fix_sign_out: |
| /* Now we get to undo what we did above. */ |
| /* ??? Is this really faster than just increasing the size of |
| the stack frame and storing X and Y in memory? */ |
| and t5, 4, AT |
| negq Y, t4 |
| cmovne AT, t4, Y |
| |
| negq X, t4 |
| cmovlbs t5, t4, X |
| negq RV, t4 |
| cmovlbs t5, t4, RV |
| |
| br $fix_sign_out_ret |
| |
| cfi_endproc |
| .size __remq, .-__remq |
| |
| DO_DIVBYZERO |
