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Diffstat (limited to 'libjpegtwrp/armv6_idct.S')
| -rw-r--r-- | libjpegtwrp/armv6_idct.S | 366 |
1 files changed, 0 insertions, 366 deletions
diff --git a/libjpegtwrp/armv6_idct.S b/libjpegtwrp/armv6_idct.S deleted file mode 100644 index 18e4e8a18..000000000 --- a/libjpegtwrp/armv6_idct.S +++ /dev/null @@ -1,366 +0,0 @@ -/* - * Copyright (C) 2010 The Android Open Source Project - * - * Licensed under the Apache License, Version 2.0 (the "License"); - * you may not use this file except in compliance with the License. - * You may obtain a copy of the License at - * - * http://www.apache.org/licenses/LICENSE-2.0 - * - * Unless required by applicable law or agreed to in writing, software - * distributed under the License is distributed on an "AS IS" BASIS, - * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - * See the License for the specific language governing permissions and - * limitations under the License. - */ - -/* - * This is a fast-and-accurate implementation of inverse Discrete Cosine - * Transform (IDCT) for ARMv6+. It also performs dequantization of the input - * coefficients just like other methods. - * - * This implementation is based on the scaled 1-D DCT algorithm proposed by - * Arai, Agui, and Nakajima. The following code is based on the figure 4-8 - * on page 52 of the JPEG textbook by Pennebaker and Mitchell. Coefficients - * are (almost) directly mapped into registers. - * - * The accuracy is achieved by using SMULWy and SMLAWy instructions. Both - * multiply 32 bits by 16 bits and store the top 32 bits of the result. It - * makes 32-bit fixed-point arithmetic possible without overflow. That is - * why jpeg_idct_ifast(), which is written in C, cannot be improved. - * - * More tricks are used to gain more speed. First of all, we use as many - * registers as possible. ARM processor has 16 registers including sp (r13) - * and pc (r15), so only 14 registers can be used without limitations. In - * general, we let r0 to r7 hold the coefficients; r10 and r11 hold four - * 16-bit constants; r12 and r14 hold two of the four arguments; and r8 hold - * intermediate value. In the second pass, r9 is the loop counter. In the - * first pass, r8 to r11 are used to hold quantization values, so the loop - * counter is held by sp. Yes, the stack pointer. Since it must be aligned - * to 4-byte boundary all the time, we align it to 32-byte boundary and use - * bit 3 to bit 5. As the result, we actually use 14.1 registers. :-) - * - * Second, we rearrange quantization values to access them sequentially. The - * table is first transposed, and the new columns are placed in the order of - * 7, 5, 1, 3, 0, 2, 4, 6. Thus we can use LDMDB to load four values at a - * time. Rearranging coefficients also helps, but that requires to change a - * dozen of files, which seems not worth it. In addition, we choose to scale - * up quantization values by 13 bits, so the coefficients are scaled up by - * 16 bits after both passes. Then we can pack and saturate them two at a - * time using PKHTB and USAT16 instructions. - * - * Third, we reorder the instructions to avoid bubbles in the pipeline. This - * is done by hand accroding to the cycle timings and the interlock behavior - * described in the technical reference manual of ARM1136JF-S. We also take - * advantage of dual issue processors by interleaving instructions with - * dependencies. It has been benchmarked on four devices and all the results - * showed distinguishable improvements. Note that PLD instructions actually - * slow things down, so they are removed at the last minute. In the future, - * this might be futher improved using a system profiler. - */ - -#ifdef __arm__ -#include <machine/cpu-features.h> -#endif - -#if __ARM_ARCH__ >= 6 - -// void armv6_idct(short *coefs, int *quans, unsigned char *rows, int col) - .arm - .text - .align - .global armv6_idct - .func armv6_idct - -armv6_idct: - // Push everything except sp (r13) and pc (r15). - stmdb sp!, {r4, r5, r6, r7, r8, r9, r10, r11, r12, r14} - - // r12 = quans, r14 = coefs. - sub r4, sp, #236 - bic sp, r4, #31 - add r5, sp, #224 - add r12, r1, #256 - stm r5, {r2, r3, r4} - add r14, r0, #16 - -pass1_head: - // Load quantization values. (q[0, 2, 4, 6]) - ldmdb r12!, {r8, r9, r10, r11} - - // Load coefficients. (c[4, 1, 2, 3, 0, 5, 6, 7]) - ldrsh r4, [r14, #-2] ! - ldrsh r1, [r14, #16] - ldrsh r2, [r14, #32] - ldrsh r3, [r14, #48] - ldrsh r0, [r14, #64] - ldrsh r5, [r14, #80] - ldrsh r6, [r14, #96] - ldrsh r7, [r14, #112] - - // r4 = q[0] * c[0]; - mul r4, r8, r4 - - // Check if ACs are all zero. - cmp r0, #0 - orreqs r8, r1, r2 - orreqs r8, r3, r5 - orreqs r8, r6, r7 - beq pass1_zero - - // Step 1: Dequantizations. - - // r2 = q[2] * c[2]; - // r0 = q[4] * c[4] + r4; - // r6 = q[6] * c[6] + r2; - mul r2, r9, r2 - mla r0, r10, r0, r4 - mla r6, r11, r6, r2 - - // Load quantization values. (q[7, 5, 1, 3]) - ldmdb r12!, {r8, r9, r10, r11} - - // r4 = r4 * 2 - r0 = -(r0 - r4 * 2); - // r2 = r2 * 2 - r6 = -(r6 - r2 * 2); - rsb r4, r0, r4, lsl #1 - rsb r2, r6, r2, lsl #1 - - // r7 = q[7] * c[7]; - // r5 = q[5] * c[5]; - // r1 = q[1] * c[1] + r7; - // r3 = q[3] * c[3] + r5; - mul r7, r8, r7 - mul r5, r9, r5 - mla r1, r10, r1, r7 - mla r3, r11, r3, r5 - - // Load constants. - ldrd r10, constants - - // Step 2: Rotations and Butterflies. - - // r7 = r1 - r7 * 2; - // r1 = r1 - r3; - // r5 = r5 * 2 - r3 = -(r3 - r5 * 2); - // r3 = r1 + r3 * 2; - // r8 = r5 + r7; - sub r7, r1, r7, lsl #1 - sub r1, r1, r3 - rsb r5, r3, r5, lsl #1 - add r3, r1, r3, lsl #1 - add r8, r5, r7 - - // r2 = r2 * 1.41421 = r2 * 27146 / 65536 + r2; - // r8 = r8 * 1.84776 / 8 = r8 * 15137 / 65536; - // r1 = r1 * 1.41421 = r1 * 27146 / 65536 + r1; - smlawt r2, r2, r10, r2 - smulwb r8, r8, r10 - smlawt r1, r1, r10, r1 - - // r0 = r0 + r6; - // r2 = r2 - r6; - // r6 = r0 - r6 * 2; - add r0, r0, r6 - sub r2, r2, r6 - sub r6, r0, r6, lsl #1 - - // r5 = r5 * -2.61313 / 8 + r8 = r5 * -21407 / 65536 + r8; - // r8 = r7 * -1.08239 / 8 + r8 = r7 * -8867 / 65536 + r8; - smlawt r5, r5, r11, r8 - smlawb r8, r7, r11, r8 - - // r4 = r4 + r2; - // r0 = r0 + r3; - // r2 = r4 - r2 * 2; - add r4, r4, r2 - add r0, r0, r3 - sub r2, r4, r2, lsl #1 - - // r7 = r5 * 8 - r3 = -(r3 - r5 * 8); - // r3 = r0 - r3 * 2; - // r1 = r1 - r7; - // r4 = r4 + r7; - // r5 = r8 * 8 - r1 = -(r1 - r8 * 8); - // r7 = r4 - r7 * 2; - rsb r7, r3, r5, lsl #3 - sub r3, r0, r3, lsl #1 - sub r1, r1, r7 - add r4, r4, r7 - rsb r5, r1, r8, lsl #3 - sub r7, r4, r7, lsl #1 - - // r2 = r2 + r1; - // r6 = r6 + r5; - // r1 = r2 - r1 * 2; - // r5 = r6 - r5 * 2; - add r2, r2, r1 - add r6, r6, r5 - sub r1, r2, r1, lsl #1 - sub r5, r6, r5, lsl #1 - - // Step 3: Reorder and Save. - - str r0, [sp, #-4] ! - str r4, [sp, #32] - str r2, [sp, #64] - str r6, [sp, #96] - str r5, [sp, #128] - str r1, [sp, #160] - str r7, [sp, #192] - str r3, [sp, #224] - b pass1_tail - - // Precomputed 16-bit constants: 27146, 15137, -21407, -8867. - // Put them in the middle since LDRD only accepts offsets from -255 to 255. - .align 3 -constants: - .word 0x6a0a3b21 - .word 0xac61dd5d - -pass1_zero: - str r4, [sp, #-4] ! - str r4, [sp, #32] - str r4, [sp, #64] - str r4, [sp, #96] - str r4, [sp, #128] - str r4, [sp, #160] - str r4, [sp, #192] - str r4, [sp, #224] - sub r12, r12, #16 - -pass1_tail: - ands r9, sp, #31 - bne pass1_head - - // r12 = rows, r14 = col. - ldr r12, [sp, #256] - ldr r14, [sp, #260] - - // Load constants. - ldrd r10, constants - -pass2_head: - // Load coefficients. (c[0, 1, 2, 3, 4, 5, 6, 7]) - ldmia sp!, {r0, r1, r2, r3, r4, r5, r6, r7} - - // r0 = r0 + 0x00808000; - add r0, r0, #0x00800000 - add r0, r0, #0x00008000 - - // Step 1: Analog to the first pass. - - // r0 = r0 + r4; - // r6 = r6 + r2; - add r0, r0, r4 - add r6, r6, r2 - - // r4 = r0 - r4 * 2; - // r2 = r2 * 2 - r6 = -(r6 - r2 * 2); - sub r4, r0, r4, lsl #1 - rsb r2, r6, r2, lsl #1 - - // r1 = r1 + r7; - // r3 = r3 + r5; - add r1, r1, r7 - add r3, r3, r5 - - // Step 2: Rotations and Butterflies. - - // r7 = r1 - r7 * 2; - // r1 = r1 - r3; - // r5 = r5 * 2 - r3 = -(r3 - r5 * 2); - // r3 = r1 + r3 * 2; - // r8 = r5 + r7; - sub r7, r1, r7, lsl #1 - sub r1, r1, r3 - rsb r5, r3, r5, lsl #1 - add r3, r1, r3, lsl #1 - add r8, r5, r7 - - // r2 = r2 * 1.41421 = r2 * 27146 / 65536 + r2; - // r8 = r8 * 1.84776 / 8 = r8 * 15137 / 65536; - // r1 = r1 * 1.41421 = r1 * 27146 / 65536 + r1; - smlawt r2, r2, r10, r2 - smulwb r8, r8, r10 - smlawt r1, r1, r10, r1 - - // r0 = r0 + r6; - // r2 = r2 - r6; - // r6 = r0 - r6 * 2; - add r0, r0, r6 - sub r2, r2, r6 - sub r6, r0, r6, lsl #1 - - // r5 = r5 * -2.61313 / 8 + r8 = r5 * -21407 / 65536 + r8; - // r8 = r7 * -1.08239 / 8 + r8 = r7 * -8867 / 65536 + r8; - smlawt r5, r5, r11, r8 - smlawb r8, r7, r11, r8 - - // r4 = r4 + r2; - // r0 = r0 + r3; - // r2 = r4 - r2 * 2; - add r4, r4, r2 - add r0, r0, r3 - sub r2, r4, r2, lsl #1 - - // r7 = r5 * 8 - r3 = -(r3 - r5 * 8); - // r3 = r0 - r3 * 2; - // r1 = r1 - r7; - // r4 = r4 + r7; - // r5 = r8 * 8 - r1 = -(r1 - r8 * 8); - // r7 = r4 - r7 * 2; - rsb r7, r3, r5, lsl #3 - sub r3, r0, r3, lsl #1 - sub r1, r1, r7 - add r4, r4, r7 - rsb r5, r1, r8, lsl #3 - sub r7, r4, r7, lsl #1 - - // r2 = r2 + r1; - // r6 = r6 + r5; - // r1 = r2 - r1 * 2; - // r5 = r6 - r5 * 2; - add r2, r2, r1 - add r6, r6, r5 - sub r1, r2, r1, lsl #1 - sub r5, r6, r5, lsl #1 - - // Step 3: Reorder and Save. - - // Load output pointer. - ldr r8, [r12], #4 - - // For little endian: r6, r2, r4, r0, r3, r7, r1, r5. - pkhtb r6, r6, r4, asr #16 - pkhtb r2, r2, r0, asr #16 - pkhtb r3, r3, r1, asr #16 - pkhtb r7, r7, r5, asr #16 - usat16 r6, #8, r6 - usat16 r2, #8, r2 - usat16 r3, #8, r3 - usat16 r7, #8, r7 - orr r0, r2, r6, lsl #8 - orr r1, r7, r3, lsl #8 - -#ifdef __ARMEB__ - // Reverse bytes for big endian. - rev r0, r0 - rev r1, r1 -#endif - - // Use STR instead of STRD to support unaligned access. - str r0, [r8, r14] ! - str r1, [r8, #4] - -pass2_tail: - adds r9, r9, #0x10000000 - bpl pass2_head - - ldr sp, [sp, #8] - add sp, sp, #236 - - ldmia sp!, {r4, r5, r6, r7, r8, r9, r10, r11, r12, r14} - bx lr - .endfunc - -#endif |