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writer/hlsl: Simplify UBO accesses for static indexing

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Use the new semantic constant value information to significantly reduce the complex indexing logic emitted for UBO accesses.
This will dramatically reduce the number of `for` loops that are decayed to `while` loops.

Change-Id: I1b0adb5edde2b4ed39c6beafc2e28106b86e0edd
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57701
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
This commit is contained in:
Ben Clayton
2021-07-13 12:18:13 +00:00
parent 71f619b6f1
commit 51cfe26bb7
46 changed files with 1712 additions and 191 deletions
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79
src/writer/hlsl/generator_impl.cc
View File

@@ -624,11 +624,27 @@ bool GeneratorImpl::EmitUniformBufferAccess(
ast::CallExpression* expr,
const transform::DecomposeMemoryAccess::Intrinsic* intrinsic) {
const auto& params = expr->params();
auto* offset_arg = builder_.Sem().Get(params[1]);
std::string scalar_offset = UniqueIdentifier("scalar_offset");
{
uint32_t scalar_offset_value = 0;
std::string scalar_offset_expr;
// If true, use scalar_offset_value, otherwise use scalar_offset_expr
bool scalar_offset_constant = false;
if (auto val = offset_arg->ConstantValue()) {
TINT_ASSERT(Writer, val.Type()->Is<sem::U32>());
scalar_offset_value = val.Elements()[0].u32;
scalar_offset_value /= 4; // bytes -> scalar index
scalar_offset_constant = true;
}
if (!scalar_offset_constant) {
// UBO offset not compile-time known.
// Calculate the scalar offset into a temporary.
scalar_offset_expr = UniqueIdentifier("scalar_offset");
auto pre = line();
pre << "const uint " << scalar_offset << " = (";
pre << "const uint " << scalar_offset_expr << " = (";
if (!EmitExpression(pre, params[1])) { // offset
return false;
}
@@ -649,32 +665,37 @@ bool GeneratorImpl::EmitUniformBufferAccess(
if (!EmitExpression(out, params[0])) { // buffer
return false;
}
out << "[" << scalar_offset << " / 4][" << scalar_offset << " % 4]";
if (scalar_offset_constant) {
char swizzle[] = {'x', 'y', 'z', 'w'};
out << "[" << (scalar_offset_value / 4) << "]."
<< swizzle[scalar_offset_value & 3];
} else {
out << "[" << scalar_offset_expr << " / 4][" << scalar_offset_expr
<< " % 4]";
}
return true;
};
// Has a minimum alignment of 8 bytes, so is either .xy or .zw
auto load_vec2 = [&] {
std::string ubo_load = UniqueIdentifier("ubo_load");
{
auto pre = line();
pre << "uint4 " << ubo_load << " = ";
if (!EmitExpression(pre, params[0])) { // buffer
if (scalar_offset_constant) {
if (!EmitExpression(out, params[0])) { // buffer
return false;
}
pre << "[" << scalar_offset << " / 4];";
out << "[" << (scalar_offset_value / 4) << "]";
out << ((scalar_offset_value & 2) == 0 ? ".xy" : ".zw");
} else {
std::string ubo_load = UniqueIdentifier("ubo_load");
{
auto pre = line();
pre << "uint4 " << ubo_load << " = ";
if (!EmitExpression(pre, params[0])) { // buffer
return false;
}
pre << "[" << scalar_offset_expr << " / 4];";
}
out << "((" << scalar_offset_expr << " & 2) ? " << ubo_load
<< ".zw : " << ubo_load << ".xy)";
}
out << "((" << scalar_offset << " & 2) ? " << ubo_load
<< ".zw : " << ubo_load << ".xy)";
return true;
};
// vec3 has a minimum alignment of 16 bytes, so is just a .xyz swizzle
auto load_vec3 = [&] {
if (!EmitExpression(out, params[0])) { // buffer
return false;
}
out << "[" << scalar_offset << " / 4].xyz";
return true;
};
// vec4 has a minimum alignment of 16 bytes, easiest case
@@ -682,7 +703,19 @@ bool GeneratorImpl::EmitUniformBufferAccess(
if (!EmitExpression(out, params[0])) { // buffer
return false;
}
out << "[" << scalar_offset << " / 4]";
if (scalar_offset_constant) {
out << "[" << (scalar_offset_value / 4) << "]";
} else {
out << "[" << scalar_offset_expr << " / 4]";
}
return true;
};
// vec3 has a minimum alignment of 16 bytes, so is just a .xyz swizzle
auto load_vec3 = [&] {
if (!load_vec4()) {
return false;
}
out << ".xyz";
return true;
};
switch (intrinsic->type) {

4
src/writer/hlsl/generator_impl_function_test.cc
View File

@@ -335,7 +335,7 @@ TEST_F(HlslGeneratorImplTest_Function,
Stage(ast::PipelineStage::kFragment),
});
GeneratorImpl& gen = Build();
GeneratorImpl& gen = SanitizeAndBuild();
ASSERT_TRUE(gen.Generate()) << gen.error();
EXPECT_EQ(gen.result(), R"(cbuffer cbuffer_ubo : register(b0, space1) {
@@ -343,7 +343,7 @@ TEST_F(HlslGeneratorImplTest_Function,
};
float sub_func(float param) {
return ubo.coord.x;
return asfloat(ubo[0].x);
}
void frag_main() {