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-rw-r--r--sysdeps/alpha/remq.S265
1 files changed, 260 insertions, 5 deletions
diff --git a/sysdeps/alpha/remq.S b/sysdeps/alpha/remq.S
index cd1064af4e..ce527d1055 100644
--- a/sysdeps/alpha/remq.S
+++ b/sysdeps/alpha/remq.S
@@ -1,6 +1,261 @@
-#define IS_REM 1
-#define SIZE 8
-#define UFUNC_NAME __remqu
-#define SFUNC_NAME __remq
+/* Copyright (C) 2004 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
-#include "divrem.h"
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#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. */
+
+ .text
+ .align 4
+ .globl __remq
+ .type __remq, @function
+ .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. */
+ stq X, 16(sp)
+ stq Y, 24(sp)
+ beq Y, DIVBYZERO
+
+ stt $f0, 0(sp)
+ stt $f1, 8(sp)
+ cfi_rel_offset ($f0, 0)
+ cfi_rel_offset ($f1, 8)
+ ldt $f0, 16(sp)
+ ldt $f1, 24(sp)
+
+ 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
+ stt $f0, 16(sp)
+
+ ldq AT, 16(sp)
+ mulq AT, Y, AT
+ ldt $f0, 0(sp)
+ cfi_restore ($f1)
+ cfi_remember_state
+ cfi_restore ($f0)
+ 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
+
+ stt $f0, 8(sp)
+ ldq Q, 8(sp)
+$fix_sign_in_ret2:
+ mulq Q, Y, QY
+ stq t4, 8(sp)
+
+ ldt $f0, 0(sp)
+ unop
+ cfi_rel_offset (t4, 8)
+ cfi_restore ($f0)
+ stq t3, 0(sp)
+ unop
+ cfi_rel_offset (t3, 0)
+
+ 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)
+ 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_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
+ stt $f0, 8(sp)
+ ldq Q, 8(sp)
+
+ 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