[Mesa-dev] [PATCH] nir/opcodes: Fix constant-folding of bitfield_insert

[Matt Turner]

On Wed, Dec 6, 2017 at 3:55 AM, James Legg <jlegg at feralinteractive.com> wrote:
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104119
> CC: <mesa-stable at lists.freedesktop.org>
> CC: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/compiler/nir/nir_opcodes.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/compiler/nir/nir_opcodes.py b/src/compiler/nir/nir_opcodes.py
> index ac7333fe78..278562b2bd 100644
> --- a/src/compiler/nir/nir_opcodes.py
> +++ b/src/compiler/nir/nir_opcodes.py
> @@ -724,12 +724,12 @@ opcode("bitfield_insert", 0, tuint32, [0, 0, 0, 0],
>  unsigned base = src0, insert = src1;
>  int offset = src2, bits = src3;
>  if (bits == 0) {
> -   dst = 0;
> +   dst = base;
>  } else if (offset < 0 || bits < 0 || bits + offset > 32) {
>     dst = 0;
>  } else {
>     unsigned mask = ((1ull << bits) - 1) << offset;
> -   dst = (base & ~mask) | ((insert << bits) & mask);
> +   dst = (base & ~mask) | ((insert << offset) & mask);
>  }
>  """)

Reviewed-by: Matt Turner <mattst88 at gmail.com>