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[Impeller] support half precision uniforms and half precision samplers #40590

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Mar 28, 2023
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[Impeller] support half precision uniforms and half precision samplers #40590

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02ccd58
[Impeller] support f16vec4 in shaders and use in solid color uniform
Mar 24, 2023
3c00839
use compiler intrinsic
Mar 24, 2023
43ff491
++
Mar 24, 2023
68b1009
++
Mar 24, 2023
b6e6f81
++
Mar 24, 2023
d739b58
Merge branch 'master' of github.com:flutter/engine into support-half-…
Mar 24, 2023
f1919b4
++
Mar 24, 2023
a98fa07
fix licenses
Mar 24, 2023
7dca490
make half a wrapper type
Mar 25, 2023
9599b62
use hardware supported conversion
Mar 25, 2023
4bdc197
disable for windows and add more conversion tests
Mar 26, 2023
a8b80ed
compile
Mar 26, 2023
8e9892b
++
Mar 26, 2023
1bce547
Merge branch 'main' into support-half-vec4
Mar 27, 2023
22a0bd1
test
Mar 27, 2023
c802c7c
Merge branch 'support-half-vec4' of github.com:jonahwilliams/engine i…
Mar 27, 2023
251564b
++
Mar 27, 2023
51d7bb7
++
Mar 27, 2023
9001fe1
Update geometry_unittests.cc
Mar 27, 2023
11f0c9f
Update geometry_unittests.cc
Mar 27, 2023
6998f76
++
Mar 27, 2023
205db32
Merge branch 'support-half-vec4' of github.com:jonahwilliams/engine i…
Mar 27, 2023
736a3e5
make this unreachable
Mar 27, 2023
0af6ab9
++
Mar 28, 2023
31cf48a
Merge branch 'main' into support-half-vec4
Mar 28, 2023
c9ffbc5
++
Mar 28, 2023
b2996a8
Merge branch 'support-half-vec4' of github.com:jonahwilliams/engine i…
Mar 28, 2023
2f1f5c3
++
Mar 28, 2023
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4 changes: 4 additions & 0 deletions ci/licenses_golden/licenses_flutter
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Original file line number Diff line number Diff line change
Expand Up @@ -1288,6 +1288,8 @@ ORIGIN: ../../../flutter/impeller/geometry/constants.h + ../../../flutter/LICENS
ORIGIN: ../../../flutter/impeller/geometry/geometry_benchmarks.cc + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/gradient.cc + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/gradient.h + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/half.cc + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/half.h + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/matrix.cc + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/matrix.h + ../../../flutter/LICENSE
ORIGIN: ../../../flutter/impeller/geometry/matrix_decomposition.cc + ../../../flutter/LICENSE
Expand Down Expand Up @@ -3828,6 +3830,8 @@ FILE: ../../../flutter/impeller/geometry/constants.h
FILE: ../../../flutter/impeller/geometry/geometry_benchmarks.cc
FILE: ../../../flutter/impeller/geometry/gradient.cc
FILE: ../../../flutter/impeller/geometry/gradient.h
FILE: ../../../flutter/impeller/geometry/half.cc
FILE: ../../../flutter/impeller/geometry/half.h
FILE: ../../../flutter/impeller/geometry/matrix.cc
FILE: ../../../flutter/impeller/geometry/matrix.h
FILE: ../../../flutter/impeller/geometry/matrix_decomposition.cc
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75 changes: 75 additions & 0 deletions impeller/compiler/reflector.cc
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Expand Up @@ -18,6 +18,7 @@
#include "impeller/compiler/code_gen_template.h"
#include "impeller/compiler/uniform_sorter.h"
#include "impeller/compiler/utilities.h"
#include "impeller/geometry/half.h"
#include "impeller/geometry/matrix.h"
#include "impeller/geometry/scalar.h"

Expand Down Expand Up @@ -534,6 +535,11 @@ static std::optional<KnownType> ReadKnownScalarType(
.name = "Scalar",
.byte_size = sizeof(Scalar),
};
case spirv_cross::SPIRType::BaseType::Half:
return KnownType{
.name = "Half",
.byte_size = sizeof(Half),
};
case spirv_cross::SPIRType::BaseType::UInt:
return KnownType{
.name = "uint32_t",
Expand Down Expand Up @@ -767,6 +773,75 @@ std::vector<StructMember> Reflector::ReadStructMembers(
continue;
}

// Tightly packed half Point (vec2).
if (member.basetype == spirv_cross::SPIRType::BaseType::Half && //
member.width == sizeof(float) * 4 && //
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@chinmaygarde chinmaygarde Mar 28, 2023

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Can you double check this? The member width doesn't make sense for half base types. I may be misunderstanding.

@jonahwilliams jonahwilliams Mar 28, 2023

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ah, this was a hack I left in. Should be sizeof(Half) * 8

member.columns == 1 && //
member.vecsize == 2 //
) {
uint32_t stride =
GetArrayStride<sizeof(HalfVector2)>(struct_type, member, i);
uint32_t element_padding = stride - sizeof(HalfVector2);
result.emplace_back(StructMember{
"HalfVector2", // type

@gaaclarke gaaclarke Mar 27, 2023

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Argument comments are of the format /*arg_name=*/: https://google.github.io/styleguide/cppguide.html#Function_Argument_Comments

@jonahwilliams jonahwilliams Mar 27, 2023

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This is following the style of the rest of the file.

@jonahwilliams jonahwilliams Mar 27, 2023 •
edited
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...also this is a struct, not a function call.

@gaaclarke gaaclarke Mar 27, 2023

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If you use /*field_name=*/ we can use the linter to verify that their name is correct. I turned this on years ago. I don't know if it still runs.

@chinmaygarde chinmaygarde Mar 28, 2023

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Not a function call, but with C++20, you can use aggregate initialization and do this without comments: {.type = "HalfVector2"}.

BaseTypeToString(member.basetype), // basetype
GetMemberNameAtIndex(struct_type, i), // name
struct_member_offset, // offset
sizeof(HalfVector2), // size
stride * array_elements.value_or(1), // byte_length
array_elements, // array_elements
element_padding, // element_padding
});
current_byte_offset += stride * array_elements.value_or(1);
continue;
}

// Tightly packed Half Float Vector3.
if (member.basetype == spirv_cross::SPIRType::BaseType::Half && //
member.width == sizeof(float) * 4 && //
member.columns == 1 && //
member.vecsize == 3 //
) {
uint32_t stride =
GetArrayStride<sizeof(HalfVector3)>(struct_type, member, i);
uint32_t element_padding = stride - sizeof(HalfVector3);
result.emplace_back(StructMember{
"HalfVector3", // type
BaseTypeToString(member.basetype), // basetype
GetMemberNameAtIndex(struct_type, i), // name
struct_member_offset, // offset
sizeof(HalfVector3), // size
stride * array_elements.value_or(1), // byte_length
array_elements, // array_elements
element_padding, // element_padding
});
current_byte_offset += stride * array_elements.value_or(1);
continue;
}

// Tightly packed Half Float Vector4.
if (member.basetype == spirv_cross::SPIRType::BaseType::Half && //
member.width == sizeof(float) * 4 && //
member.columns == 1 && //
member.vecsize == 4 //
) {
uint32_t stride =
GetArrayStride<sizeof(HalfVector4)>(struct_type, member, i);
uint32_t element_padding = stride - sizeof(HalfVector4);
result.emplace_back(StructMember{
"HalfVector4", // type
BaseTypeToString(member.basetype), // basetype
GetMemberNameAtIndex(struct_type, i), // name
struct_member_offset, // offset
sizeof(HalfVector4), // size
stride * array_elements.value_or(1), // byte_length
array_elements, // array_elements
element_padding, // element_padding
});
current_byte_offset += stride * array_elements.value_or(1);
continue;
}

// Other isolated scalars (like bool, int, float/Scalar, etc..).
{
auto maybe_known_type = ReadKnownScalarType(member.basetype);
Expand Down
3 changes: 3 additions & 0 deletions impeller/compiler/shader_lib/impeller/types.glsl
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Expand Up @@ -6,6 +6,8 @@
#define TYPES_GLSL_

#extension GL_AMD_gpu_shader_half_float : enable
#extension GL_AMD_gpu_shader_half_float_fetch : enable
#extension GL_EXT_shader_explicit_arithmetic_types_float16 : enable

#ifndef IMPELLER_TARGET_METAL

Expand All @@ -17,6 +19,7 @@ precision mediump float;
#define f16vec3 vec3
#define f16vec4 vec4
#define f16mat4 mat4
#define f16sampler2D sampler2D

#endif // IMPELLER_TARGET_METAL

Expand Down
4 changes: 2 additions & 2 deletions impeller/entity/shaders/solid_fill.frag
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Expand Up @@ -5,11 +5,11 @@
#include <impeller/types.glsl>

uniform FragInfo {
vec4 color;
f16vec4 color;

@dnfield dnfield Mar 24, 2023

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Doesn't this require #extension GL_EXT_shader_16bit_storage : require up top?

@jonahwilliams jonahwilliams Mar 24, 2023

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It does not, I'm not actually using a f16vec4 on glsl, here is the compiled shader:

#version 100
precision mediump float;
precision highp int;

struct FragInfo
{
    vec4 color;
};

uniform FragInfo frag_info;

void main()
{
    gl_FragData[0] = frag_info.color;
}

@jonahwilliams jonahwilliams Mar 24, 2023

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oh - but this is all in types.glsl too

}
frag_info;

out vec4 frag_color;
out f16vec4 frag_color;

void main() {
frag_color = frag_info.color;
Expand Down
2 changes: 2 additions & 0 deletions impeller/geometry/BUILD.gn
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Expand Up @@ -12,6 +12,8 @@ impeller_component("geometry") {
"constants.h",
"gradient.cc",
"gradient.h",
"half.cc",
"half.h",
"matrix.cc",
"matrix.h",
"matrix_decomposition.cc",
Expand Down
12 changes: 12 additions & 0 deletions impeller/geometry/geometry_unittests.cc
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Expand Up @@ -10,6 +10,7 @@
#include "flutter/testing/testing.h"
#include "impeller/geometry/constants.h"
#include "impeller/geometry/gradient.h"
#include "impeller/geometry/half.h"
#include "impeller/geometry/path.h"
#include "impeller/geometry/path_builder.h"
#include "impeller/geometry/path_component.h"
Expand Down Expand Up @@ -2086,5 +2087,16 @@ TEST(GeometryTest, Gradient) {
}
}

TEST(GeometryTest, Half) {
ASSERT_EQ(ScalarToHalf(0.0), 0.0f16);
ASSERT_EQ(ScalarToHalf(0.05), 0.05f16);
ASSERT_EQ(ScalarToHalf(2.43), 2.43f16);
ASSERT_EQ(ScalarToHalf(-1.45), -1.45f16);

// 65504 is the largest possible half.
ASSERT_EQ(ScalarToHalf(65504.0f), 65504.0f16);
ASSERT_EQ(ScalarToHalf(65504.0f + 1), 65504.0f16);
}

} // namespace testing
} // namespace impeller
13 changes: 13 additions & 0 deletions impeller/geometry/half.cc
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@@ -0,0 +1,13 @@
// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "half.h"

@gaaclarke gaaclarke Mar 27, 2023

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(this should be based from the project root too)

@jonahwilliams jonahwilliams Mar 27, 2023

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oops!


namespace impeller {

_Float16 ScalarToHalf(Scalar f) {
return static_cast<_Float16>(f);
}

} // namespace impeller
93 changes: 93 additions & 0 deletions impeller/geometry/half.h
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@@ -0,0 +1,93 @@
// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <cstdint>

#include "color.h"
#include "point.h"
#include "scalar.h"
#include "vector.h"

@gaaclarke gaaclarke Mar 27, 2023

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Includes should be rooted at the base of the project as seen above: https://google.github.io/styleguide/cppguide.html#Names_and_Order_of_Includes

@jonahwilliams jonahwilliams Mar 27, 2023

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Done


namespace impeller {

/// @brief Convert a scalar to a half precision float.
///
/// See also: https://clang.llvm.org/docs/LanguageExtensions.html
_Float16 ScalarToHalf(Scalar f);

/// @brief A storage only class for half precision floating point.
struct Half {
_Float16 x = 0;

Half() = default;

Half(Scalar value) : x(ScalarToHalf(value)) {}
};

/// @brief A storage only class for half precision floating point vector 4.
struct HalfVector4 {

@chinmaygarde chinmaygarde Mar 28, 2023

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Did templating the existing Scalar type vectors not work? This is fine too but seems like we can dry this up.

@jonahwilliams jonahwilliams Mar 28, 2023

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I did this above and backed it out. The big caveat is that 1) We need implicit constructor conversion to make the headers work 2) we generally don't want to ever use these in the backend besides that as it implies we're dropping precision before we need to. There is no performance improvement to be gained from this. In addition, if we end up needing to emulate _Float16 support for windows we'll likely end up needing to using uint16_t as a storage type and then we'd have to define all of the operators to make that work.

Given all that, I'd really rather just leave them as storage only conversions.

union {
struct {
_Float16 x = 0;
_Float16 y = 0;
_Float16 z = 0;
_Float16 w = 0;
};
_Float16 e[4];
};

constexpr HalfVector4() {}

constexpr HalfVector4(const Color& a)
: x(ScalarToHalf(a.red)),
y(ScalarToHalf(a.green)),
z(ScalarToHalf(a.green)),
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w(ScalarToHalf(a.alpha)){};

constexpr HalfVector4(const Vector4& a)
: x(ScalarToHalf(a.x)),
y(ScalarToHalf(a.y)),
z(ScalarToHalf(a.z)),
w(ScalarToHalf(a.w)){};
};

/// @brief A storage only class for half precision floating point vector 3.
struct HalfVector3 {
union {
struct {
_Float16 x = 0;
_Float16 y = 0;
_Float16 z = 0;
};
_Float16 e[3];
};

constexpr HalfVector3(){};

constexpr HalfVector3(const Vector3& a)
: x(ScalarToHalf(a.x)), y(ScalarToHalf(a.y)), z(ScalarToHalf(a.z)){};
};

/// @brief A storage only class for half precision floating point vector 2.
struct HalfVector2 {
union {
struct {
_Float16 x = 0;
_Float16 y = 0;
};
_Float16 e[2];
};

constexpr HalfVector2(){};

constexpr HalfVector2(const Vector2& a)
: x(ScalarToHalf(a.x)), y(ScalarToHalf(a.y)){};
};

static_assert(sizeof(Half) == sizeof(uint16_t));
static_assert(sizeof(HalfVector2) == 2 * sizeof(Half));
static_assert(sizeof(HalfVector3) == 3 * sizeof(Half));
static_assert(sizeof(HalfVector4) == 4 * sizeof(Half));

} // namespace impeller
1 change: 1 addition & 0 deletions impeller/renderer/shader_types.h
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Expand Up @@ -11,6 +11,7 @@

#include "flutter/fml/hash_combine.h"
#include "flutter/fml/logging.h"
#include "impeller/geometry/half.h"
#include "impeller/geometry/matrix.h"
#include "impeller/runtime_stage/runtime_types.h"

Expand Down