1 files changed, 273 insertions, 0 deletions
diff --git a/ports/sysdeps/alpha/divq.S b/ports/sysdeps/alpha/divq.S
new file mode 100644
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+++ b/ports/sysdeps/alpha/divq.S
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+/* Copyright (C) 2004 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 divide.  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	__divq
+	.type	__divq, @funcnoplt
+	.usepv	__divq, no
+
+	cfi_startproc
+	cfi_return_column (RA)
+__divq:
+	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 and clean up.  */
+	cvttq/c	$f0, $f0
+	excb
+	mt_fpcr	$f3
+	_FTOIT	$f0, RV, 16
+
+	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)
+	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	RV		/* quotient */
+#define R	t0		/* 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 result should be negative.
+		bit 2:	set if X was negated.
+		bit 3:	set if Y was negated.
+	*/
+	xor	X, Y, AT
+	cmplt	AT, 0, t5
+	cmplt	X, 0, AT
+	negq	X, t0
+
+	s4addq	AT, t5, t5
+	cmovne	AT, t0, X
+	cmplt	Y, 0, AT
+	negq	Y, t0
+
+	s8addq	AT, t5, t5
+	cmovne	AT, t0, Y
+	unop
+	blbc	t5, $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, 8, AT
+	negq	Y, t4
+	cmovne	AT, t4, Y
+
+	and	t5, 4, AT
+	negq	X, t4
+	cmovne	AT, t4, X
+
+	negq	RV, t4
+	cmovlbs	t5, t4, RV
+
+	br	$fix_sign_out_ret
+
+	cfi_endproc
+	.size	__divq, .-__divq
+
+	DO_DIVBYZERO