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| author | Katerina Barone-Adesi <katerinab@gmail.com> | 2014-05-19 17:27:52 +0200 |
|---|---|---|
| committer | Michael Niedermayer <michaelni@gmx.at> | 2014-05-20 04:21:06 +0200 |
| commit | e50ae60d46181814245f70b61b70394311e10373 (patch) | |
| tree | 84197bc05af463440414de72ca6620299e564586 /libavcodec/simple_idct_template.c | |
| parent | 7d25af1547f8d97231f1c6e4cab7ad2bbf1dd071 (diff) | |
| download | ffmpeg-e50ae60d46181814245f70b61b70394311e10373.tar.gz | |
avcodec/fate-idct8x8: Defined behavior: eliminate negative left-shifts.
The original code left-shifts negative values, which is undefined
in the C99 specification (the one used during normal FFmpeg compilation).
This change multiplies by (1 << shift), which is functionally equivalent,
but has defined behavior.
With this change, fate-idct8x8 compiled with --fsanitize=undefined works.
Bug-Id: 686
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
The assembly generated by gcc is unchanged by this commit
Diffstat (limited to 'libavcodec/simple_idct_template.c')
| -rw-r--r-- | libavcodec/simple_idct_template.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/libavcodec/simple_idct_template.c b/libavcodec/simple_idct_template.c index 95844a2f33..789db8d0ac 100644 --- a/libavcodec/simple_idct_template.c +++ b/libavcodec/simple_idct_template.c @@ -110,12 +110,12 @@ static inline void FUNC(idctRowCondDC)(int16_t *row, int extra_shift) if (((((uint64_t *)row)[0] & ~ROW0_MASK) | ((uint64_t *)row)[1]) == 0) { uint64_t temp; if (DC_SHIFT - extra_shift >= 0) { - temp = (row[0] << (DC_SHIFT - extra_shift)) & 0xffff; + temp = (row[0] * (1 << (DC_SHIFT - extra_shift))) & 0xffff; } else { temp = ((row[0] + (1<<(extra_shift - DC_SHIFT-1))) >> (extra_shift - DC_SHIFT)) & 0xffff; } - temp += temp << 16; - temp += temp << 32; + temp += temp * (1 << 16); + temp += temp * ((uint64_t) 1 << 32); ((uint64_t *)row)[0] = temp; ((uint64_t *)row)[1] = temp; return; @@ -127,11 +127,11 @@ static inline void FUNC(idctRowCondDC)(int16_t *row, int extra_shift) row[1])) { uint32_t temp; if (DC_SHIFT - extra_shift >= 0) { - temp = (row[0] << (DC_SHIFT - extra_shift)) & 0xffff; + temp = (row[0] * (1 << (DC_SHIFT - extra_shift))) & 0xffff; } else { temp = ((row[0] + (1<<(extra_shift - DC_SHIFT-1))) >> (extra_shift - DC_SHIFT)) & 0xffff; } - temp += temp << 16; + temp += temp * (1 << 16); ((uint32_t*)row)[0]=((uint32_t*)row)[1] = ((uint32_t*)row)[2]=((uint32_t*)row)[3] = temp; return; |