ARM assembler optimised LPC decode routine for FLAC (not yet enabled).
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@8927 a1c6a512-1295-4272-9138-f99709370657
diff --git a/apps/codecs/libffmpegFLAC/arm.S b/apps/codecs/libffmpegFLAC/arm.S
new file mode 100644
index 0000000..eba2251
--- /dev/null
+++ b/apps/codecs/libffmpegFLAC/arm.S
@@ -0,0 +1,265 @@
+/***************************************************************************
+ * __________ __ ___.
+ * Open \______ \ ____ ____ | | _\_ |__ _______ ___
+ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
+ * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
+ * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
+ * \/ \/ \/ \/ \/
+ * $Id$
+ *
+ * Copyright (C) 2006 by Thom Johansen
+ *
+ * All files in this archive are subject to the GNU General Public License.
+ * See the file COPYING in the source tree root for full license agreement.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+/* The following is an assembler optimised version of the LPC filtering
+ routines needed for FLAC decoding. It is optimised for use with ARM
+ processors.
+ All LPC filtering up to order 9 is done in specially optimised unrolled
+ loops, while every order above this is handled by a slower default routine.
+ */
+ .section .icode,"ax",%progbits
+ .global lpc_decode_arm
+lpc_decode_arm:
+ stmdb sp!, { r4-r11, lr }
+ ldr r4, [sp, #36]
+ /* r0 = blocksize, r1 = qlevel, r2 = pred_order
+ r3 = data, r4 = coeffs
+ */
+
+ /* the data pointer always lags behind history pointer by 'pred_order'
+ samples. since we have one loop for each order, we can hard code this
+ and free a register by not saving data pointer.
+ */
+ sub r3, r3, r2, lsl #2 @ r3 = history
+ cmp r0, #0 @ no samples to process
+ beq .exit
+ cmp r2, #9 @ check if order is too high for unrolled loops
+ addls pc, pc, r2, lsl #2 @ jump to our unrolled decode loop if it exists
+@ jumptable:
+ b .default @ order too high, go to default routine
+ b .exit @ zero order filter isn't possible, exit function
+ b .order1
+ b .order2
+ b .order3
+ b .order4
+ b .order5
+ b .order6
+ b .order7
+ b .order8
+
+@ last jump table entry coincides with target, so leave it out
+.order9:
+ ldmia r4, { r5-r12, r14 } @ fetch coefs
+.loop9:
+ ldr r4, [r3], #4 @ load first history sample
+ mul r2, r4, r14 @ multiply with last coef
+ ldr r4, [r3], #4 @ rinse and repeat while accumulating sum in r2
+ mla r2, r4, r12, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r11, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r10, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r9, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r8, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r7, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r6, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r5, r2
+ ldr r4, [r3] @ r4 = residual
+ add r2, r4, r2, asr r1 @ shift sum by qlevel bits and add residual
+ str r2, [r3], #-8*4 @ save result and wrap history pointer back
+ subs r0, r0, #1 @ check if we're done
+ bne .loop9 @ nope, jump back
+ b .exit
+
+.order8:
+ ldmia r4, { r5-r12 }
+.loop8:
+ @ we have more registers to spare here, so start block reading
+ ldmia r3!, { r4, r14 }
+ mul r2, r4, r12
+ mla r2, r14, r11, r2
+ ldmia r3!, { r4, r14 }
+ mla r2, r4, r10, r2
+ mla r2, r14, r9, r2
+ ldmia r3!, { r4, r14 }
+ mla r2, r4, r8, r2
+ mla r2, r14, r7, r2
+ ldmia r3!, { r4, r14 }
+ mla r2, r4, r6, r2
+ mla r2, r14, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-7*4
+ subs r0, r0, #1
+ bne .loop8
+ b .exit
+
+.order7:
+ ldmia r4, { r5-r11 }
+.loop7:
+ ldmia r3!, { r4, r12, r14 }
+ mul r2, r4, r11
+ mla r2, r12, r10, r2
+ mla r2, r14, r9, r2
+ ldmia r3!, { r4, r12, r14 }
+ mla r2, r4, r8, r2
+ mla r2, r12, r7, r2
+ mla r2, r14, r6, r2
+ ldr r4, [r3], #4
+ mla r2, r4, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-6*4
+ subs r0, r0, #1
+ bne .loop7
+ b .exit
+
+.order6:
+ ldmia r4, { r5-r10 }
+.loop6:
+ ldmia r3!, { r4, r11-r12, r14 }
+ mul r2, r4, r10
+ mla r2, r11, r9, r2
+ mla r2, r12, r8, r2
+ mla r2, r14, r7, r2
+ ldmia r3!, { r4, r11 }
+ mla r2, r4, r6, r2
+ mla r2, r11, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-5*4
+ subs r0, r0, #1
+ bne .loop6
+ b .exit
+
+.order5:
+ ldmia r4, { r5-r9 }
+.loop5:
+ ldmia r3!, { r4, r10-r12, r14 }
+ mul r2, r4, r9
+ mla r2, r10, r8, r2
+ mla r2, r11, r7, r2
+ mla r2, r12, r6, r2
+ mla r2, r14, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-4*4
+ subs r0, r0, #1
+ bne .loop5
+ b .exit
+
+.order4:
+ ldmia r4, { r5-r8 }
+.loop4:
+ ldmia r3!, { r4, r11-r12, r14 }
+ mul r2, r4, r8
+ mla r2, r11, r7, r2
+ mla r2, r12, r6, r2
+ mla r2, r14, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-3*4
+ subs r0, r0, #1
+ bne .loop4
+ b .exit
+
+.order3:
+ ldmia r4, { r5-r7 }
+.loop3:
+ ldmia r3!, { r4, r12, r14 }
+ mul r2, r4, r7
+ mla r2, r12, r6, r2
+ mla r2, r14, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-2*4
+ subs r0, r0, #1
+ bne .loop3
+ b .exit
+
+.order2:
+ ldmia r4, { r5-r6 }
+.loop2:
+ ldmia r3!, { r4, r14 }
+ mul r2, r4, r6
+ mla r2, r14, r5, r2
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #-1*4
+ subs r0, r0, #1
+ bne .loop2
+ b .exit
+
+.order1:
+ ldr r5, [r4]
+ ldr r4, [r3], #4
+.loop1:
+ mul r2, r4, r5
+ ldr r4, [r3]
+ add r2, r4, r2, asr r1
+ str r2, [r3], #4
+ subs r0, r0, #1
+ bne .loop1
+ b .exit
+
+.default:
+ /* we do the filtering in an unrolled by 4 loop as far as we can, and then
+ do the rest by jump table. */
+ add r5, r4, r2, lsl #2 @ need to start in the other end of coefs
+ mov r6, r3 @ working copy of history pointer
+ mov r7, r2, lsr #2 @ r7 = coefs/4
+ mov r14, #0 @ init accumulator
+.dloop1:
+ ldmdb r5!, { r8-r11 }
+ ldr r12, [r6], #4
+ mla r14, r12, r11, r14
+ ldr r12, [r6], #4
+ mla r14, r12, r10, r14
+ ldr r12, [r6], #4
+ mla r14, r12, r9, r14
+ ldr r12, [r6], #4
+ mla r14, r12, r8, r14
+ subs r7, r7, #1
+ bne .dloop1
+
+ and r7, r2, #3 @ get remaining samples to be filtered
+ add pc, pc, r7, lsl #2 @ jump into accumulator chain
+@ jumptable:
+ b .dsave @ padding
+ b .dsave
+ b .oneleft
+ b .twoleft
+@ implicit .threeleft
+ ldr r12, [r5, #-4]!
+ ldr r8, [r6], #4
+ mla r14, r12, r8, r14
+.twoleft:
+ ldr r12, [r5, #-4]!
+ ldr r8, [r6], #4
+ mla r14, r12, r8, r14
+.oneleft:
+ ldr r12, [r5, #-4]!
+ ldr r8, [r6], #4
+ mla r14, r12, r8, r14
+
+.dsave:
+ ldr r12, [r6] @ load residual
+ add r14, r12, r14, asr r1 @ shift sum by qlevel bits and add residual
+ str r14, [r6] @ store result
+ add r3, r3, #4 @ increment history pointer
+ subs r0, r0, #1 @ are we done?
+ bne .default @ no, prepare for next sample
+
+.exit:
+ ldmia sp!, { r4-r11, pc }
diff --git a/apps/codecs/libffmpegFLAC/arm.h b/apps/codecs/libffmpegFLAC/arm.h
new file mode 100644
index 0000000..39080d7
--- /dev/null
+++ b/apps/codecs/libffmpegFLAC/arm.h
@@ -0,0 +1,8 @@
+#ifndef _FLAC_ARM_H
+#define _FLAC_ARM_H
+
+#include "bitstream.h"
+
+void lpc_decode_arm(int blocksize, int qlevel, int pred_order, int32_t* data, int* coeffs);
+
+#endif