[Mesa-dev] [PATCH 06/45] nir: Handle fp16 rounding modes at nir_type_conversion_op
Eduardo Lima Mitev
elima at igalia.com
Fri Aug 18 11:31:05 UTC 2017
On 08/17/2017 09:08 PM, Jason Ekstrand wrote:
> On Thu, Jul 13, 2017 at 7:35 AM, Alejandro Piñeiro <apinheiro at igalia.com
> <mailto:apinheiro at igalia.com>> wrote:
>
> From: Jose Maria Casanova Crespo <jmcasanova at igalia.com
> <mailto:jmcasanova at igalia.com>>
>
> nir_type_conversion enables new operations to handle rounding modes to
> convert to fp16 values. Two new opcodes are enabled nir_op_f2f16_rtne
> and nir_op_f2f16_rtz.
>
> The undefined behaviour doesn't has any effect and uses the original
> nir_op_f2f16 operation.
> ---
> src/compiler/glsl/glsl_to_nir.cpp | 3 ++-
> src/compiler/nir/nir.h | 3 ++-
> src/compiler/nir/nir_opcodes.py | 10 ++++++++--
> src/compiler/nir/nir_opcodes_c.py | 15 ++++++++++++++-
> src/compiler/spirv/vtn_alu.c | 2 +-
> 5 files changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/src/compiler/glsl/glsl_to_nir.cpp
> b/src/compiler/glsl/glsl_to_nir.cpp
> index 2153004..23e6121 100644
> --- a/src/compiler/glsl/glsl_to_nir.cpp
> +++ b/src/compiler/glsl/glsl_to_nir.cpp
> @@ -1509,7 +1509,8 @@ nir_visitor::visit(ir_expression *ir)
> case ir_unop_u642i64: {
> nir_alu_type src_type =
> nir_get_nir_type_for_glsl_base_type(types[0]);
> nir_alu_type dst_type =
> nir_get_nir_type_for_glsl_base_type(out_type);
> - result = nir_build_alu(&b, nir_type_conversion_op(src_type,
> dst_type),
> + result = nir_build_alu(&b, nir_type_conversion_op(src_type,
> dst_type,
> + nir_rounding_mode_undef),
> srcs[0], NULL, NULL, NULL);
> /* b2i and b2f don't have fixed bit-size versions so the
> builder will
> * just assume 32 and we have to fix it up here.
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 115ec1b..7e48e18 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -741,7 +741,8 @@ nir_get_nir_type_for_glsl_type(const struct
> glsl_type *type)
> return
> nir_get_nir_type_for_glsl_base_type(glsl_get_base_type(type));
> }
>
> -nir_op nir_type_conversion_op(nir_alu_type src, nir_alu_type dst);
> +nir_op nir_type_conversion_op(nir_alu_type src, nir_alu_type dst,
> + nir_rounding_mode rnd);
>
> typedef enum {
> NIR_OP_IS_COMMUTATIVE = (1 << 0),
> diff --git a/src/compiler/nir/nir_opcodes.py
> b/src/compiler/nir/nir_opcodes.py
> index 39c01a7..bd342de 100644
> --- a/src/compiler/nir/nir_opcodes.py
> +++ b/src/compiler/nir/nir_opcodes.py
> @@ -179,8 +179,14 @@ for src_t in [tint, tuint, tfloat]:
> else:
> bit_sizes = [8, 16, 32, 64]
> for bit_size in bit_sizes:
> - unop_convert("{0}2{1}{2}".format(src_t[0], dst_t[0],
> bit_size),
> - dst_t + str(bit_size), src_t, "src0")
> + if bit_size == 16 and dst_t == tfloat and src_t == tfloat:
> + rnd_modes = ['rtne', 'rtz']
> + for rnd_mode in rnd_modes:
> + unop_convert("{0}2{1}{2}_{3}".format(src_t[0],
> dst_t[0],
> + bit_size,
> rnd_mode),
> + dst_t + str(bit_size), src_t, "src0")
> + unop_convert("{0}2{1}{2}".format(src_t[0], dst_t[0],
> bit_size),
> + dst_t + str(bit_size), src_t, "src0")
>
>
> You could do this a bit shorter if you make rnd_modes = ['', '_rtne',
> 'rtz'] and then just loop over them.
>
Hmm, I don't think we can reduce it that way. Notice that the loop over
rnd_modes is only for bit_size==16, but the last unop_convert call,
outside the loop, applies to all bit sizes.
>
>
> # We'll hand-code the to/from bool conversion opcodes. Because
> bool doesn't
> # have multiple bit-sizes, we can always infer the size from the
> other type.
> diff --git a/src/compiler/nir/nir_opcodes_c.py
> b/src/compiler/nir/nir_opcodes_c.py
> index a1db54f..a7721d3 100644
> --- a/src/compiler/nir/nir_opcodes_c.py
> +++ b/src/compiler/nir/nir_opcodes_c.py
> @@ -30,7 +30,7 @@ template = Template("""
> #include "nir.h"
>
> nir_op
> -nir_type_conversion_op(nir_alu_type src, nir_alu_type dst)
> +nir_type_conversion_op(nir_alu_type src, nir_alu_type dst,
> nir_rounding_mode rnd)
> {
> nir_alu_type src_base = (nir_alu_type)
> nir_alu_type_get_base_type(src);
> nir_alu_type dst_base = (nir_alu_type)
> nir_alu_type_get_base_type(dst);
> @@ -64,7 +64,20 @@ nir_type_conversion_op(nir_alu_type src,
> nir_alu_type dst)
> switch (dst_bit_size) {
> % for dst_bits in [32, 64]:
> case ${dst_bits}:
> +% if src_t == 'float' and dst_t == 'float' and
> dst_bits == 16:
> + switch(rnd) {
> +% for rnd_t in ['rtne' , 'rtz']:
> + case nir_rounding_mode_${rnd_t}:
> + return
> ${'nir_op_{0}2{1}{2}_{3}'.format(src_t[0], dst_t[0],
> +
> dst_bits, rnd_t)};
> +% endfor
> + default:
>
>
> This default makes me a bit uncomfortable. I think I'd rather
> assert-fail if it's a rounding mode we don't have an opcode for.
> Otherwise, this function is just silently ignoring rounding modes which
> seems bad.
>
Ok, we'll fix that.
>
> + return
> ${'nir_op_{0}2{1}{2}'.format(src_t[0], dst_t[0],
> +
> dst_bits)};
> + }
> +% else:
>
>
> The indentation on the above is a bit weird. I'm not really sure what
> to do with it. What I would say is that you shouldn't worry too much
> about making the resulting C nicely indented. Just make the generator
> readable.
>
Ok, note taken.
>
> return ${'nir_op_{0}2{1}{2}'.format(src_t[0],
> dst_t[0], dst_bits)};
> +% endif
> % endfor
> default:
> unreachable("Invalid nir alu bit size");
> diff --git a/src/compiler/spirv/vtn_alu.c b/src/compiler/spirv/vtn_alu.c
> index ecf9cbc..7ec30b8 100644
> --- a/src/compiler/spirv/vtn_alu.c
> +++ b/src/compiler/spirv/vtn_alu.c
> @@ -355,7 +355,7 @@ vtn_nir_alu_op_for_spirv_opcode(SpvOp opcode,
> bool *swap,
> case SpvOpConvertUToF:
> case SpvOpSConvert:
> case SpvOpFConvert:
> - return nir_type_conversion_op(src, dst);
> + return nir_type_conversion_op(src, dst, nir_rounding_mode_undef);
>
> /* Derivatives: */
> case SpvOpDPdx: return nir_op_fddx;
> --
> 2.9.3
>
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