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Skip clipping in the inverse wht transform C implementation

The spec requires that the final residual values of a compliant
bitstream must be representable in bitdepth+1 bits, which is not
possible if intermediate values are large enough to be clipped.

--- a/src/itx_tmpl.c

+++ b/src/itx_tmpl.c

@@ -161,9 +161,6 @@

                                        coef *const coeff, const int eob

                                        HIGHBD_DECL_SUFFIX)

 {

-    const int bitdepth = bitdepth_from_max(bitdepth_max);

-    const int col_clip_max = (1 << (imax(bitdepth + 6, 16) - 1)) -1;

-    const int col_clip_min = -col_clip_max - 1;

     int32_t tmp[4 * 4], out[4], in_mem[4];

     for (int i = 0; i < 4; i++) {

@@ -171,8 +168,6 @@

             in_mem[j] = coeff[i + j * 4];

         dav1d_inv_wht4_1d_c(in_mem, 1, &tmp[i * 4], 1, 0);

     }

-    for (int k = 0; k < 4 * 4; k++)

-        tmp[k] = iclip(tmp[k], col_clip_min, col_clip_max);

     for (int i = 0; i < 4; i++) {

         dav1d_inv_wht4_1d_c(&tmp[i], 4, out, 1, 1);