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lavc/vc1dsp: fix potential overflow in R-V V inv_trans_4

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Judging by the coefficients, the last round of add/sub can overflow
to 17 bits with a very small probability just as with the 8-point
transform. This is not observed under FATE, but better safe than sorry.
This commit is contained in:
Rémi Denis-Courmont 2024-06-27 22:00:05 +03:00
parent 349c49fd1b
commit b818dff8d8
1 changed files with 8 additions and 7 deletions
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15
libavcodec/riscv/vc1dsp_rvv.S
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@ -202,13 +202,14 @@ func ff_vc1_inv_trans_4_rvv, zve32x
vmul.vx v20, v1, t2
vadd.vv v26, v14, v16 # t3
vsub.vv v27, v18, v20 # t4
vadd.vv v0, v24, v26
vsub.vv v1, v25, v27
vadd.vv v2, v25, v27
vsub.vv v3, v24, v26
.irp n,0,1,2,3
vssra.vx v\n, v\n, t1 # + 4 >> 3 or + 64 >> 7
.endr
vwadd.vv v8, v24, v26
vwsub.vv v10, v25, v27
vwadd.vv v12, v25, v27
vwsub.vv v14, v24, v26
vnclip.wx v0, v8, t1
vnclip.wx v1, v10, t1
vnclip.wx v2, v12, t1
vnclip.wx v3, v14, t1
jr t0
endfunc