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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/jrevdct.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/jrevdct.c')
| -rw-r--r-- | libavcodec/jrevdct.c | 36 |
1 files changed, 18 insertions, 18 deletions
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; } } |