From e50ae60d46181814245f70b61b70394311e10373 Mon Sep 17 00:00:00 2001 From: Katerina Barone-Adesi Date: Mon, 19 May 2014 17:27:52 +0200 Subject: 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 The assembly generated by gcc is unchanged by this commit --- libavcodec/simple_idct_template.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'libavcodec/simple_idct_template.c') 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; -- cgit v1.2.3