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atrac3: use the QMF window's symmetry in the ARMv4 filter
The dewindowing loop is 72% of ATRAC3 decoding on ARM7TDMI. The window is symmetric, so read only its first half: each pair of coefficients serves two inputs from the front of the 48 and, with the two swapped, two from the back. That halves the coefficient loads and lets them be done four at a time. The sums are kept in 64 bits, so the new order of the additions does not change the result: the PCM output of seven files is byte-identical. Estimated with perfsim for the Sansa e200v1 (not measured on the device), atrac3_lp2_132.oma: 53.74 -> 48.81 MHz. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Michael Giacomelli
parent
b8861e3f09
commit
3966b420a3
1 changed files with 44 additions and 51 deletions
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@ -92,48 +92,35 @@ atrac3_iqmf_matrixing:
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* in += 2;
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* out += 2;
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* }
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*
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* The window is symmetric, win[i] = win[47-i], so only its first half is
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* read: win[2k] and win[2k+1] serve in[2k] and in[2k+1] from the front of
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* the 48 inputs and, swapped, in[46-2k] and in[47-2k] from the back. That
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* is 24 coefficient loads for an output pair where there were 48, and
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* they can be loaded four at a time. The sums are kept in 64 bits, so the
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* order of the additions does not change the result.
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*
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* Note: r12 is a scratch register and can be used without restorage.
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****************************************************************************/
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/* To be called as first block to call smull for initial filling of the result
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* registers lr/r9 and r12/r8. */
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#define DEWIN_8_SAMPLES_MUL_ASM \
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ldmia r2!, {r4, r5}; /* load win[0..1] */ \
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ldmia r1!, {r6, r7}; /* load in [0..1] */ \
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smull lr , r9, r4, r6; /* s1 = win[0] * in[0] */ \
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smull r12, r8, r5, r7; /* s2 = win[1] * in[1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */
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/* Called after first block. Will always multiply-add to the result registers
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* lr/r9 and r12/r8. */
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#define DEWIN_8_SAMPLES_MLA_ASM \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */ \
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ldmia r2!, {r4, r5}; /* load win[i..i+1] */ \
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ldmia r1!, {r6, r7}; /* load in [i..i+1] */ \
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smlal lr , r9, r4, r6; /* s1 = win[i ] * in[i ] */ \
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smlal r12, r8, r5, r7; /* s2 = win[i+1] * in[i+1] */
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/* Eight taps: coefficients win[2k..2k+3], two input pairs from the front
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* (r1) and two from the back (r3). s1 is lr/r9 and s2 is r12/r8. The
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* samples are the last operand of the multiplies, as they are the smaller
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* one and that is what the multiplier's early termination goes by. */
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#define DEWIN_8_SAMPLES_ASM(first1, first2) \
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ldmia r2!, {r4-r7}; /* load win[2k..2k+3] */ \
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ldmia r1!, {r10, r11}; /* load in[2k], in[2k+1] */ \
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first1 lr , r9, r4, r10; /* s1 += win[2k ] * in[2k ] */ \
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first2 r12, r8, r5, r11; /* s2 += win[2k+1] * in[2k+1] */ \
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ldmdb r3!, {r10, r11}; /* load in[46-2k], in[47-2k] */ \
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smlal lr , r9, r5, r10; /* s1 += win[2k+1] * in[46-2k] */ \
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smlal r12, r8, r4, r11; /* s2 += win[2k ] * in[47-2k] */ \
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ldmia r1!, {r10, r11}; /* load in[2k+2], in[2k+3] */ \
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smlal lr , r9, r6, r10; /* s1 += win[2k+2] * in[2k+2] */ \
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smlal r12, r8, r7, r11; /* s2 += win[2k+3] * in[2k+3] */ \
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ldmdb r3!, {r10, r11}; /* load in[44-2k], in[45-2k] */ \
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smlal lr , r9, r7, r10; /* s1 += win[2k+3] * in[44-2k] */ \
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smlal r12, r8, r6, r11; /* s2 += win[2k+2] * in[45-2k] */
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.align 2
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.global atrac3_iqmf_dewindowing
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@ -144,16 +131,19 @@ atrac3_iqmf_dewindowing:
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/* r1 = input samples */
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/* r2 = window coefficients */
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/* r3 = counter */
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stmfd sp!, {r4-r9, lr} /* save non-scratch registers */
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stmfd sp!, {r4-r11, lr} /* save non-scratch registers */
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add r3, r0, r3, lsl #3 /* end of dest: two words a count */
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stmfd sp!, {r3}
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add r3, r1, #192 /* r3 = end of the 48 inputs */
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.iqmf_dewindow_outer_loop: /* outer loop 0...counter-1 */
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DEWIN_8_SAMPLES_MUL_ASM /* 0.. 7, use "MUL" macro here! */
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DEWIN_8_SAMPLES_MLA_ASM /* 8..15 */
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DEWIN_8_SAMPLES_MLA_ASM /* 16..23 */
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DEWIN_8_SAMPLES_MLA_ASM /* 24..31 */
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DEWIN_8_SAMPLES_MLA_ASM /* 32..39 */
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DEWIN_8_SAMPLES_MLA_ASM /* 40..47 */
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DEWIN_8_SAMPLES_ASM(smull, smull) /* in[ 0.. 3], in[44..47] */
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DEWIN_8_SAMPLES_ASM(smlal, smlal) /* in[ 4.. 7], in[40..43] */
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DEWIN_8_SAMPLES_ASM(smlal, smlal) /* in[ 8..11], in[36..39] */
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DEWIN_8_SAMPLES_ASM(smlal, smlal) /* in[12..15], in[32..35] */
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DEWIN_8_SAMPLES_ASM(smlal, smlal) /* in[16..19], in[28..31] */
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DEWIN_8_SAMPLES_ASM(smlal, smlal) /* in[20..23], in[24..27] */
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mov lr , lr , lsr #31
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orr r9, lr , r9, lsl #1 /* s1 = low>>31 || hi<<1 */
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@ -161,13 +151,16 @@ atrac3_iqmf_dewindowing:
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orr r8, r12, r8, lsl #1 /* s2 = low>>31 || hi<<1 */
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stmia r0!, {r8, r9} /* store result out[0]=s2, out[1]=s1 */
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sub r1, r1, #184 /* roll back 46 entries = 184 bytes */
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sub r2, r2, #192 /* roll back 48 entries = 192 bytes = win[0] */
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ldr r4, [sp] /* end of dest */
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sub r1, r1, #88 /* back 24 entries, on 2: in += 2 */
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add r3, r3, #104 /* on 24 entries, and 2 more */
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sub r2, r2, #96 /* roll back 24 entries = win[0] */
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subs r3, r3, #1 /* outer loop -= 1 */
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bgt .iqmf_dewindow_outer_loop
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cmp r0, r4
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bne .iqmf_dewindow_outer_loop
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ldmpc regs=r4-r9 /* restore registers */
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add sp, sp, #4
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ldmpc regs=r4-r11 /* restore registers */
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.atrac3_iqmf_dewindowing_end:
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.size atrac3_iqmf_dewindowing,.atrac3_iqmf_dewindowing_end-atrac3_iqmf_dewindowing
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