Commit 7f821289 authored by Juan Suárez Romero's avatar Juan Suárez Romero

Revert "nir/lower_double_ops: relax lower mod()"

This reverts commit 8172b1fa.

This commit was done taking in account Vulkan spec, but did not realize
it was affecting OpenGL too.

Closes: #2252
parent a4db9a15
Pipeline #90882 passed with stages
in 20 minutes and 8 seconds
......@@ -426,24 +426,15 @@ lower_mod(nir_builder *b, nir_ssa_def *src0, nir_ssa_def *src1)
*
* If the division is lowered, it could add some rounding errors that make
* floor() to return the quotient minus one when x = N * y. If this is the
* case, we should return zero because mod(x, y) output value is [0, y).
* But fortunately Vulkan spec allows this kind of errors; from Vulkan
* spec, appendix A (Precision and Operation of SPIR-V instructions:
*
* "The OpFRem and OpFMod instructions use cheap approximations of
* remainder, and the error can be large due to the discontinuity in
* trunc() and floor(). This can produce mathematically unexpected
* results in some cases, such as FMod(x,x) computing x rather than 0,
* and can also cause the result to have a different sign than the
* infinitely precise result."
*
* In practice this means the output value is actually in the interval
* [0, y].
*
* case, we return zero because mod(x, y) output value is [0, y).
*/
nir_ssa_def *floor = nir_ffloor(b, nir_fdiv(b, src0, src1));
nir_ssa_def *mod = nir_fsub(b, src0, nir_fmul(b, src1, floor));
return nir_fsub(b, src0, nir_fmul(b, src1, floor));
return nir_bcsel(b,
nir_fne(b, mod, src1),
mod,
nir_imm_double(b, 0.0));
}
static nir_ssa_def *
......
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