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Code Issues Releases Activity

avfilter/vf_fsppdsp: Fix left shifts of negative numbers

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They are undefined behavior and UBSan warns about them
(in the checkasm test). Put the shifts in the constants
instead. This even gives a tiny speedup here:

Old benchmarks:
column_fidct_c:                                       3369.9 ( 1.00x)
column_fidct_sse2:                                     829.1 ( 4.06x)
New benchmarks:
column_fidct_c:                                       3304.2 ( 1.00x)
column_fidct_sse2:                                     827.9 ( 3.99x)

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-11-13 11:57:02 +01:00
parent f8bcea4946
commit ddf443f1e9
1 changed files with 23 additions and 23 deletions
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40
libavfilter/vf_fsppdsp.c
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@@ -165,7 +165,7 @@ void ff_column_fidct_c(const int16_t *restrict thr_adr, const int16_t *restrict
d0 = tmp10 + tmp11;
d4 = tmp10 - tmp11;
z1 = MULTIPLY16H((tmp12 + tmp13) << 2, FIX_0_707106781);
z1 = MULTIPLY16H(tmp12 + tmp13, FIX_0_707106781 << 2);
d2 = tmp13 + z1;
d6 = tmp13 - z1;
@@ -193,10 +193,10 @@ void ff_column_fidct_c(const int16_t *restrict thr_adr, const int16_t *restrict
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;
z5 = MULTIPLY16H((tmp10 - tmp12) << 2, FIX_0_382683433);
z2 = MULTIPLY16H(tmp10 << 2, FIX_0_541196100) + z5;
z4 = MULTIPLY16H(tmp12 << 2, FIX_1_306562965) + z5;
z3 = MULTIPLY16H(tmp11 << 2, FIX_0_707106781);
z5 = MULTIPLY16H(tmp10 - tmp12, FIX_0_382683433 << 2);
z2 = MULTIPLY16H(tmp10, FIX_0_541196100 << 2) + z5;
z4 = MULTIPLY16H(tmp12, FIX_1_306562965 << 2) + z5;
z3 = MULTIPLY16H(tmp11, FIX_0_707106781 << 2);
z11 = tmp7 + z3;
z13 = tmp7 - z3;
@@ -215,12 +215,12 @@ void ff_column_fidct_c(const int16_t *restrict thr_adr, const int16_t *restrict
//Simd version uses here a shortcut for the tmp5,tmp6,tmp7 == 0
z13 = tmp6 + tmp5;
z10 = (tmp6 - tmp5) << 1;
z10 = (tmp6 - tmp5) * 2;
z11 = tmp4 + tmp7;
z12 = (tmp4 - tmp7) << 1;
z12 = (tmp4 - tmp7) * 2;
tmp7 = (z11 + z13) >> 2; //+2 !
tmp11 = MULTIPLY16H((z11 - z13) << 1, FIX_1_414213562);
tmp11 = MULTIPLY16H(z11 - z13, FIX_1_414213562 << 1);
z5 = MULTIPLY16H(z10 + z12, FIX_1_847759065);
tmp10 = MULTIPLY16H(z12, FIX_1_082392200) - z5;
tmp12 = MULTIPLY16H(z10, FIX_2_613125930) + z5; // - !!
@@ -264,7 +264,7 @@ void ff_row_idct_c(const int16_t *restrict wsptr, int16_t *restrict output_adr,
tmp11 = wsptr[2] - wsptr[3];
tmp13 = wsptr[0] + wsptr[1];
tmp12 = (MULTIPLY16H(wsptr[0] - wsptr[1], FIX_1_414213562_A) << 2) - tmp13;//this shift order to avoid overflow
tmp12 = (MULTIPLY16H(wsptr[0] - wsptr[1], FIX_1_414213562_A) * 4) - tmp13;//this shift order to avoid overflow
tmp0 = tmp10 + tmp13; //->temps
tmp3 = tmp10 - tmp13; //->temps
@@ -289,9 +289,9 @@ void ff_row_idct_c(const int16_t *restrict wsptr, int16_t *restrict output_adr,
tmp10 = MULTIPLY16H(z12, FIX_1_082392200) - z5;
tmp12 = MULTIPLY16H(z10, FIX_2_613125930) + z5; // - FIX_
tmp6 = (tmp12 << 3) - tmp7;
tmp5 = (tmp11 << 3) - tmp6;
tmp4 = (tmp10 << 3) + tmp5;
tmp6 = tmp12 * 8 - tmp7;
tmp5 = tmp11 * 8 - tmp6;
tmp4 = tmp10 * 8 + tmp5;
// Final output stage: descale and write column
outptr[0 * output_stride] += DESCALE(tmp0 + tmp7, 3);
@@ -342,20 +342,20 @@ void ff_row_fdct_c(int16_t *restrict data, const uint8_t *restrict pixels,
dataptr[2] = tmp10 + tmp11;
dataptr[3] = tmp10 - tmp11;
z1 = MULTIPLY16H((tmp12 + tmp13) << 2, FIX_0_707106781);
z1 = MULTIPLY16H(tmp12 + tmp13, FIX_0_707106781 << 2);
dataptr[0] = tmp13 + z1;
dataptr[1] = tmp13 - z1;
// Odd part
tmp10 = (tmp4 + tmp5) << 2;
tmp11 = (tmp5 + tmp6) << 2;
tmp12 = (tmp6 + tmp7) << 2;
tmp10 = tmp4 + tmp5;
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;
z5 = MULTIPLY16H(tmp10 - tmp12, FIX_0_382683433);
z2 = MULTIPLY16H(tmp10, FIX_0_541196100) + z5;
z4 = MULTIPLY16H(tmp12, FIX_1_306562965) + z5;
z3 = MULTIPLY16H(tmp11, FIX_0_707106781);
z5 = MULTIPLY16H(tmp10 - tmp12, FIX_0_382683433 << 2);
z2 = MULTIPLY16H(tmp10, FIX_0_541196100 << 2) + z5;
z4 = MULTIPLY16H(tmp12, FIX_1_306562965 << 2) + z5;
z3 = MULTIPLY16H(tmp11, FIX_0_707106781 << 2);
z11 = tmp7 + z3;
z13 = tmp7 - z3;