On Mon, Jan 4, 2016 at 12:44 PM, Matt Turner <matts...@gmail.com> wrote: > On Wed, Dec 30, 2015 at 4:26 PM, Ilia Mirkin <imir...@alum.mit.edu> wrote: >> On Wed, Dec 30, 2015 at 3:26 PM, Matt Turner <matts...@gmail.com> wrote: >>> The OpenGL specifications for these functions say: >>> >>> The result will be undefined if <offset> or <bits> is negative, or if >>> the sum of <offset> and <bits> is greater than the number of bits >>> used to store the operand. >>> >>> Therefore passing bits=32, offset=0 is legal and defined in GLSL. >>> >>> But the earlier DX11/SM5 bfi/ibfe/ubfe opcodes are specified to accept a >>> bitfield width ranging from 0-31. As such, Intel and AMD instructions >>> read only the low 5 bits of the width operand, making them not compliant >>> with the GLSL spec, so we have to special case the bits=32 case. >>> >>> Checking that offset=0 is not necessary, since for any other value, >>> <offset> + <bits> will be greater than 32, which is specified as >>> generating an undefined result. >>> >>> Fixes: >>> ES31-CTS.shader_bitfield_operation.bitfieldInsert.uint_2 >>> ES31-CTS.shader_bitfield_operation.bitfieldInsert.uvec4_3 >>> ES31-CTS.shader_bitfield_operation.bitfieldExtract.uvec3_0 >>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92595 >>> --- >>> Yuck. Suggestions welcome. >> >> Can you make a piglit test? Want to see if nvidia has the same >> problem. According to >> http://docs.nvidia.com/cuda/parallel-thread-execution/#integer-arithmetic-instructions-bfe, >> offset/bits can actually be up to 255 (although I can't fully imagine >> why one might want that). However perhaps the HW differs. > > I just sent: [PATCH] arb_gpu_shader5: Test corner cases of > bitfieldInsert/bitfieldExtract. > > It's not totally tested (as in, I haven't fixed i965 to make it pass > because I found out that the bfi2 instruction is also broken...) but I > am curious to see what the proprietary NVIDIA driver does.
I'm curious too. On nvc0 the new bitfieldExtract tests still pass, but bitfieldInsert now fails. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
