Move udiv32_arm.S into libdemac, as this divider is specialized for the APE codec and an optimized divider is already provided for general use in codeclib.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24506 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 300 insertions, 0 deletions

diff --git a/apps/codecs/demac/libdemac/udiv32_arm.S b/apps/codecs/demac/libdemac/udiv32_arm.S
new file mode 100644
index 0000000000..4492492d30
--- /dev/null
+++ b/apps/codecs/demac/libdemac/udiv32_arm.S
@@ -0,0 +1,300 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2008 by Jens Arnold
+ * Copyright (C) 2009 by Andrew Mahone
+ *
+ * Optimised unsigned integer division for ARMv4
+ *
+ * Based on: libgcc routines for ARM cpu, additional algorithms from ARM System
+ *           Developer's Guide
+ * Division routines, written by Richard Earnshaw, (rearnsha@armltd.co.uk)
+ * Copyright 1995, 1996, 1998, 1999, 2000, 2003, 2004, 2005
+ * Free Software Foundation, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "config.h"
+/* Codecs should not normally do this, but we need to check a macro, and
+ * codecs.h would confuse the assembler. */
+
+#ifdef USE_IRAM
+#define DIV_RECIP
+    .section    .icode,"ax",%progbits
+#else
+    .text
+#endif
+    .align
+    .global udiv32_arm
+    .type   udiv32_arm,%function
+
+#if ARM_ARCH < 5
+/* Adapted from an algorithm given in ARM System Developer's Guide (7.3.1.2)
+   for dividing a 30-bit value by a 15-bit value, with two operations per
+   iteration by storing quotient and remainder together and adding the previous
+   quotient bit during trial subtraction. Modified to work with any dividend
+   and divisor both less than 1 << 30, and skipping trials by calculating bits
+   in output. */
+.macro ARM_DIV_31_BODY dividend, divisor, result, bits, curbit, quotient, remainder
+
+    mov     \bits, #1
+    /* Shift the divisor left until it aligns with the numerator. If it already
+       has the high bit set, this is fine, everything inside .rept will be
+       skipped, and the add before and adcs after will set the one-bit result
+       to zero. */
+    cmn     \divisor, \dividend, lsr #16
+    movcs   \divisor, \divisor, lsl #16
+    addcs   \bits, \bits, #16
+    cmn     \divisor, \dividend, lsr #8
+    movcs   \divisor, \divisor, lsl #8
+    addcs   \bits, \bits, #8
+    cmn     \divisor, \dividend, lsr #4
+    movcs   \divisor, \divisor, lsl #4
+    addcs   \bits, \bits, #4
+    cmn     \divisor, \dividend, lsr #2
+    movcs   \divisor, \divisor, lsl #2
+    addcs   \bits, \bits, #2
+    cmn     \divisor, \dividend, lsr #1
+    movcs   \divisor, \divisor, lsl #1
+    addcs   \bits, \bits, #1
+    adds    \result, \dividend, \divisor
+    subcc   \result, \result, \divisor
+    rsb     \curbit, \bits, #31
+    add     pc, pc, \curbit, lsl #3
+    nop
+    .rept   30
+    adcs    \result, \divisor, \result, lsl #1
+    /* Fix the remainder portion of the result. This must be done because the
+       handler for 32-bit numerators needs the remainder. */
+    subcc   \result, \result, \divisor
+    .endr
+    /* Shift remainder/quotient left one, add final quotient bit */
+    adc     \result, \result, \result
+    mov     \remainder, \result, lsr \bits
+    eor     \quotient, \result, \remainder, lsl \bits
+.endm
+
+#ifdef CPU_PP
+#if CONFIG_CPU == PP5020
+.set recip_max, 8384
+#elif CONFIG_CPU == PP5002
+.set recip_max, 4608
+#else
+.set recip_max, 16384
+#endif
+#elif CONFIG_CPU == AS3525
+.set recip_max, 42752
+#elif CONFIG_CPU == S5L8701
+.set recip_max, 12800
+#elif CONFIG_CPU == S5L8700
+.set recip_max, 9088
+#endif
+
+udiv32_arm:
+#ifdef DIV_RECIP
+    cmp     r1, #3
+    bcc     .L_udiv_tiny
+    cmp     r1, #recip_max
+    bhi     .L_udiv
+    adr     r3, .L_udiv_recip_table-12
+    ldr     r2, [r3, r1, lsl #2]
+    mov     r3, r0
+    umull   ip, r0, r2, r0
+    mul     r2, r0, r1
+    cmp     r3, r2
+    bxcs    lr
+    sub     r0, r0, #1
+    bx      lr
+.L_udiv_tiny:
+    cmp     r1, #1
+    movhi   r0, r0, lsr #1
+    bxcs    lr
+    b       .L_div0
+#endif
+.L_udiv:
+    /* Invert divisor. ARM_DIV_31_BODY uses adc to both subtract the divisor
+       and add the next bit of the result. The correction code at .L_udiv32
+       does not need the divisor inverted, but can be modified to work with it,
+       and this allows the zero divisor test to be done early and without an
+       explicit comparison. */
+    rsbs    r1, r1, #0
+#ifndef DIV_RECIP
+    beq .L_div0
+#endif
+    tst     r0, r0
+    /* High bit must be unset, otherwise shift numerator right, calculate,
+       and correct results. As this case is very uncommon we want to avoid
+       any other delays on the main path in handling it, so the long divide
+       calls the short divide as a function. */
+    bmi     .L_udiv32
+.L_udiv31:
+    ARM_DIV_31_BODY r0, r1, r2, r3, ip, r0, r1
+    bx      lr
+.L_udiv32:
+    /* store original numerator and divisor, we'll need them to correct the
+       result, */
+    stmdb   sp, { r0, r1, lr }
+    /* Call __div0 here if divisor is zero, otherwise it would report the wrong
+       address. */
+    mov     r0, r0, lsr #1
+    bl      .L_udiv31
+    ldmdb   sp, { r2, r3, lr }
+    /* Move the low bit of the original numerator to the carry bit */
+    movs    r2, r2, lsr #1
+    /* Shift the remainder left one and add in the carry bit */
+    adc     r1, r1, r1
+    /* Subtract the original divisor from the remainder, setting carry if the
+       result is non-negative */
+    adds    r1, r1, r3
+    /* Shift quotient left one and add carry bit */
+    adc     r0, r0, r0
+    bx      lr
+.L_div0:
+    /* __div0 expects the calling address on the top of the stack */
+    stmdb sp!, { lr }
+    mov     r0, #0
+#if defined(__ARM_EABI__) || !defined(USE_IRAM)
+    bl      __div0
+#else
+    ldr     pc, [pc, #-4]
+    .word   __div0
+#endif
+#ifdef DIV_RECIP
+.L_udiv_recip_table:
+    .set div, 3
+    .rept recip_max - 2
+        .if (div - 1) & div
+            .set q, 0x40000000 / div
+            .set r, (0x40000000 - (q * div))<<1
+            .set q, q << 1
+            .if r >= div
+                .set q, q + 1
+                .set r, r - div
+            .endif
+            .set r, r << 1
+            .set q, q << 1
+            .if r >= div
+                .set q, q + 1
+                .set r, r - div
+            .endif
+            .set q, q + 1
+        .else
+            .set q, 0x40000000 / div * 4
+        .endif
+        .word q
+        .set div, div+1
+    .endr
+#endif
+    .size udiv32_arm, . - udiv32_arm
+
+#else
+.macro ARMV5_UDIV32_BODY numerator, divisor, quotient, bits, inv, neg, div0label
+    cmp     \numerator, \divisor
+    clz     \bits, \divisor
+    bcc     30f
+    mov     \inv, \divisor, lsl \bits
+    add     \neg, pc, \inv, lsr #25
+    cmp     \inv, #1<<31
+    ldrhib  \inv, [\neg, #.L_udiv_est_table-.-64]
+    bls     20f
+    subs    \bits, \bits, #7
+    rsb     \neg, \divisor, #0
+    movpl   \divisor, \inv, lsl \bits
+    bmi     10f
+    mul     \inv, \divisor, \neg
+    smlawt  \divisor, \divisor, \inv, \divisor
+    mul     \inv, \divisor, \neg
+    /* This will save a cycle on ARMv6, but does not produce a correct result
+       if numerator sign bit is set. This case accounts for about 1 in 10^7 of
+       divisions, done by the APE decoder, so we specialize for the more common
+       case and handle the uncommon large-numerator separately */
+#if ARM_ARCH >= 6
+    tst     \numerator, \numerator
+    smmla   \divisor, \divisor, \inv, \divisor
+    bmi     40f
+    smmul   \inv, \numerator, \divisor
+#else
+    mov     \bits, #0
+    smlal   \bits, \divisor, \inv, \divisor
+    umull   \bits, \inv, \numerator, \divisor
+#endif
+    add     \numerator, \numerator, \neg
+    mla     \divisor, \inv, \neg, \numerator
+    mov     \quotient, \inv
+    cmn     \divisor, \neg
+    addcc   \quotient, \quotient, #1
+    addpl   \quotient, \quotient, #2
+    bx      lr
+10:
+    rsb     \bits, \bits, #0
+    sub     \inv, \inv, #4
+    mov     \divisor, \inv, lsr \bits
+    umull   \bits, \inv, \numerator, \divisor
+    mla     \divisor, \inv, \neg, \numerator
+    mov     \quotient, \inv
+    cmn     \neg, \divisor, lsr #1
+    addcs   \divisor, \divisor, \neg, lsl #1
+    addcs   \quotient, \quotient, #2
+    cmn     \neg, \divisor
+    addcs   \quotient, \quotient, #1
+    bx      lr
+20:
+.ifnc "", "\div0label"
+    rsb     \bits, \bits, #31
+    bne     \div0label
+.endif
+    mov     \quotient, \numerator, lsr \bits
+    bx      lr
+30:
+    mov     \quotient, #0
+    bx      lr
+#if ARM_ARCH >= 6
+40:
+    umull   \bits, \inv, \numerator, \divisor
+    add     \numerator, \numerator, \neg
+    mla     \divisor, \inv, \neg, \numerator
+    mov     \quotient, \inv
+    cmn     \divisor, \neg
+    addcc   \quotient, \quotient, #1
+    addpl   \quotient, \quotient, #2
+    bx      lr
+#endif
+.endm
+
+udiv32_arm:
+    ARMV5_UDIV32_BODY r0, r1, r0, r2, r3, ip, .L_div0
+.L_div0:
+    /* __div0 expects the calling address on the top of the stack */
+    stmdb sp!, { lr }
+    mov     r0, #0
+#if defined(__ARM_EABI__) || !defined(USE_IRAM)
+    bl      __div0
+#else
+    ldr     pc, [pc, #-4]
+    .word   __div0
+#endif
+.L_udiv_est_table:
+    .byte 0xff, 0xfc, 0xf8, 0xf4, 0xf0, 0xed, 0xea, 0xe6
+    .byte 0xe3, 0xe0, 0xdd, 0xda, 0xd7, 0xd4, 0xd2, 0xcf
+    .byte 0xcc, 0xca, 0xc7, 0xc5, 0xc3, 0xc0, 0xbe, 0xbc
+    .byte 0xba, 0xb8, 0xb6, 0xb4, 0xb2, 0xb0, 0xae, 0xac
+    .byte 0xaa, 0xa8, 0xa7, 0xa5, 0xa3, 0xa2, 0xa0, 0x9f
+    .byte 0x9d, 0x9c, 0x9a, 0x99, 0x97, 0x96, 0x94, 0x93
+    .byte 0x92, 0x90, 0x8f, 0x8e, 0x8d, 0x8c, 0x8a, 0x89
+    .byte 0x88, 0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81
+#endif
+    .size udiv32_arm, . - udiv32_arm