From e50ae60d46181814245f70b61b70394311e10373 Mon Sep 17 00:00:00 2001 From: Katerina Barone-Adesi Date: Mon, 19 May 2014 17:27:52 +0200 Subject: [PATCH] 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/jfdctint_template.c | 4 ++-- libavcodec/jrevdct.c | 36 +++++++++++++++---------------- libavcodec/simple_idct_template.c | 10 ++++----- 3 files changed, 25 insertions(+), 25 deletions(-) diff --git a/libavcodec/jfdctint_template.c b/libavcodec/jfdctint_template.c index c6a1638107..3ea2f5dadc 100644 --- a/libavcodec/jfdctint_template.c +++ b/libavcodec/jfdctint_template.c @@ -216,8 +216,8 @@ static av_always_inline void FUNC(row_fdct)(int16_t *data) tmp11 = tmp1 + tmp2; tmp12 = tmp1 - tmp2; - dataptr[0] = (int16_t) ((tmp10 + tmp11) << PASS1_BITS); - dataptr[4] = (int16_t) ((tmp10 - tmp11) << PASS1_BITS); + dataptr[0] = (int16_t) ((tmp10 + tmp11) * (1 << PASS1_BITS)); + dataptr[4] = (int16_t) ((tmp10 - tmp11) * (1 << PASS1_BITS)); z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100); dataptr[2] = (int16_t) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865), diff --git a/libavcodec/jrevdct.c b/libavcodec/jrevdct.c index 91780b2e44..d4e6571acc 100644 --- a/libavcodec/jrevdct.c +++ b/libavcodec/jrevdct.c @@ -249,8 +249,8 @@ void ff_j_rev_dct(DCTBLOCK data) /* AC terms all zero */ if (d0) { /* Compute a 32 bit value to assign. */ - int16_t dcval = (int16_t) (d0 << PASS1_BITS); - register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000); + int16_t dcval = (int16_t) (d0 * (1 << PASS1_BITS)); + register int v = (dcval & 0xffff) | ((dcval * (1 << 16)) & 0xffff0000); idataptr[0] = v; idataptr[1] = v; @@ -272,8 +272,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -284,8 +284,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = MULTIPLY(-d6, FIX_1_306562965); tmp3 = MULTIPLY(d6, FIX_0_541196100); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -298,8 +298,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = MULTIPLY(d2, FIX_0_541196100); tmp3 = MULTIPLY(d2, FIX_1_306562965); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -307,8 +307,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp12 = tmp1 - tmp2; } else { /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */ - tmp10 = tmp13 = (d0 + d4) << CONST_BITS; - tmp11 = tmp12 = (d0 - d4) << CONST_BITS; + tmp10 = tmp13 = (d0 + d4) * CONST_SCALE; + tmp11 = tmp12 = (d0 - d4) * CONST_SCALE; } } @@ -618,8 +618,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -630,8 +630,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = MULTIPLY(-d6, FIX_1_306562965); tmp3 = MULTIPLY(d6, FIX_0_541196100); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -644,8 +644,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp2 = MULTIPLY(d2, FIX_0_541196100); tmp3 = MULTIPLY(d2, FIX_1_306562965); - tmp0 = (d0 + d4) << CONST_BITS; - tmp1 = (d0 - d4) << CONST_BITS; + tmp0 = (d0 + d4) * CONST_SCALE; + tmp1 = (d0 - d4) * CONST_SCALE; tmp10 = tmp0 + tmp3; tmp13 = tmp0 - tmp3; @@ -653,8 +653,8 @@ void ff_j_rev_dct(DCTBLOCK data) tmp12 = tmp1 - tmp2; } else { /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */ - tmp10 = tmp13 = (d0 + d4) << CONST_BITS; - tmp11 = tmp12 = (d0 - d4) << CONST_BITS; + tmp10 = tmp13 = (d0 + d4) * CONST_SCALE; + tmp11 = tmp12 = (d0 - d4) * CONST_SCALE; } } 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;