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[naga] Remove unused types and global expressions in a single pass.
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In compaction, correctly identify unused types and global expressions,
rather than treating all global expressions referred to by
`PendingArraySize::Expression` array lengths as used even if the array
type itself is not.

This is tested by checking that going from expression to type and
back, along with the opposite, is correctly marked as used. It also
checks that adding an unused type using an expression gets compacted
out.

See the comments on `ModuleTracer::type_expression_tandem` for
details.

Fixes #6788.
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@kentslaney @jimblandy
kentslaney authored and jimblandy committed Jan 23, 2025
1 parent 0282d61 commit 3cd2e7c
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -364,6 +364,7 @@ By @ErichDonGubler in [#6456](https://github.com/gfx-rs/wgpu/pull/6456), [#6148]
- In validation, forbid cycles between global expressions and types. By @jimblandy in [#6800](https://github.com/gfx-rs/wgpu-pull/6800)
- Allow abstract scalars in modf and frexp results. By @jimblandy in [#6821](https://github.com/gfx-rs/wgpu-pull/6821)
- In the WGSL front end, apply automatic conversions to values being assigned. By @jimblandy in [#6822](https://github.com/gfx-rs/wgpu-pull/6822)
- Fix a leak by ensuring that types that depend on expressions are correctly compacted. By @KentSlaney in [#6934](https://github.com/gfx-rs/wgpu/pull/6934).

#### Vulkan

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313 changes: 158 additions & 155 deletions naga/src/compact/expressions.rs
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Expand Up @@ -62,168 +62,171 @@ impl ExpressionTracer<'_> {
}

log::trace!("tracing new expression {:?}", expr);
self.trace_expression(expr);
}
}

use crate::Expression as Ex;
match *expr {
// Expressions that do not contain handles that need to be traced.
Ex::Literal(_)
| Ex::FunctionArgument(_)
| Ex::GlobalVariable(_)
| Ex::LocalVariable(_)
| Ex::CallResult(_)
| Ex::SubgroupBallotResult
| Ex::RayQueryProceedResult => {}
pub fn trace_expression(&mut self, expr: &crate::Expression) {
use crate::Expression as Ex;
match *expr {
// Expressions that do not contain handles that need to be traced.
Ex::Literal(_)
| Ex::FunctionArgument(_)
| Ex::GlobalVariable(_)
| Ex::LocalVariable(_)
| Ex::CallResult(_)
| Ex::SubgroupBallotResult
| Ex::RayQueryProceedResult => {}

Ex::Constant(handle) => {
self.constants_used.insert(handle);
// Constants and expressions are mutually recursive, which
// complicates our nice one-pass algorithm. However, since
// constants don't refer to each other, we can get around
// this by looking *through* each constant and marking its
// initializer as used. Since `expr` refers to the constant,
// and the constant refers to the initializer, it must
// precede `expr` in the arena.
let init = self.constants[handle].init;
match self.global_expressions_used {
Some(ref mut used) => used.insert(init),
None => self.expressions_used.insert(init),
};
}
Ex::Override(_) => {
// All overrides are considered used by definition. We mark
// their types and initialization expressions as used in
// `compact::compact`, so we have no more work to do here.
}
Ex::ZeroValue(ty) => {
self.types_used.insert(ty);
}
Ex::Compose { ty, ref components } => {
self.types_used.insert(ty);
self.expressions_used
.insert_iter(components.iter().cloned());
}
Ex::Access { base, index } => self.expressions_used.insert_iter([base, index]),
Ex::AccessIndex { base, index: _ } => {
self.expressions_used.insert(base);
}
Ex::Splat { size: _, value } => {
self.expressions_used.insert(value);
}
Ex::Swizzle {
size: _,
vector,
pattern: _,
} => {
self.expressions_used.insert(vector);
}
Ex::Load { pointer } => {
self.expressions_used.insert(pointer);
}
Ex::ImageSample {
image,
sampler,
gather: _,
coordinate,
array_index,
offset,
ref level,
depth_ref,
} => {
self.expressions_used
.insert_iter([image, sampler, coordinate]);
self.expressions_used.insert_iter(array_index);
match self.global_expressions_used {
Some(ref mut used) => used.insert_iter(offset),
None => self.expressions_used.insert_iter(offset),
}
use crate::SampleLevel as Sl;
match *level {
Sl::Auto | Sl::Zero => {}
Sl::Exact(expr) | Sl::Bias(expr) => {
self.expressions_used.insert(expr);
}
Sl::Gradient { x, y } => self.expressions_used.insert_iter([x, y]),
}
self.expressions_used.insert_iter(depth_ref);
}
Ex::ImageLoad {
image,
coordinate,
array_index,
sample,
level,
} => {
self.expressions_used.insert(image);
self.expressions_used.insert(coordinate);
self.expressions_used.insert_iter(array_index);
self.expressions_used.insert_iter(sample);
self.expressions_used.insert_iter(level);
Ex::Constant(handle) => {
self.constants_used.insert(handle);
// Constants and expressions are mutually recursive, which
// complicates our nice one-pass algorithm. However, since
// constants don't refer to each other, we can get around
// this by looking *through* each constant and marking its
// initializer as used. Since `expr` refers to the constant,
// and the constant refers to the initializer, it must
// precede `expr` in the arena.
let init = self.constants[handle].init;
match self.global_expressions_used {
Some(ref mut used) => used.insert(init),
None => self.expressions_used.insert(init),
};
}
Ex::Override(_) => {
// All overrides are considered used by definition. We mark
// their types and initialization expressions as used in
// `compact::compact`, so we have no more work to do here.
}
Ex::ZeroValue(ty) => {
self.types_used.insert(ty);
}
Ex::Compose { ty, ref components } => {
self.types_used.insert(ty);
self.expressions_used
.insert_iter(components.iter().cloned());
}
Ex::Access { base, index } => self.expressions_used.insert_iter([base, index]),
Ex::AccessIndex { base, index: _ } => {
self.expressions_used.insert(base);
}
Ex::Splat { size: _, value } => {
self.expressions_used.insert(value);
}
Ex::Swizzle {
size: _,
vector,
pattern: _,
} => {
self.expressions_used.insert(vector);
}
Ex::Load { pointer } => {
self.expressions_used.insert(pointer);
}
Ex::ImageSample {
image,
sampler,
gather: _,
coordinate,
array_index,
offset,
ref level,
depth_ref,
} => {
self.expressions_used
.insert_iter([image, sampler, coordinate]);
self.expressions_used.insert_iter(array_index);
match self.global_expressions_used {
Some(ref mut used) => used.insert_iter(offset),
None => self.expressions_used.insert_iter(offset),
}
Ex::ImageQuery { image, ref query } => {
self.expressions_used.insert(image);
use crate::ImageQuery as Iq;
match *query {
Iq::Size { level } => self.expressions_used.insert_iter(level),
Iq::NumLevels | Iq::NumLayers | Iq::NumSamples => {}
use crate::SampleLevel as Sl;
match *level {
Sl::Auto | Sl::Zero => {}
Sl::Exact(expr) | Sl::Bias(expr) => {
self.expressions_used.insert(expr);
}
Sl::Gradient { x, y } => self.expressions_used.insert_iter([x, y]),
}
Ex::Unary { op: _, expr } => {
self.expressions_used.insert(expr);
}
Ex::Binary { op: _, left, right } => {
self.expressions_used.insert_iter([left, right]);
}
Ex::Select {
condition,
accept,
reject,
} => self
.expressions_used
.insert_iter([condition, accept, reject]),
Ex::Derivative {
axis: _,
ctrl: _,
expr,
} => {
self.expressions_used.insert(expr);
}
Ex::Relational { fun: _, argument } => {
self.expressions_used.insert(argument);
}
Ex::Math {
fun: _,
arg,
arg1,
arg2,
arg3,
} => {
self.expressions_used.insert(arg);
self.expressions_used.insert_iter(arg1);
self.expressions_used.insert_iter(arg2);
self.expressions_used.insert_iter(arg3);
}
Ex::As {
expr,
kind: _,
convert: _,
} => {
self.expressions_used.insert(expr);
}
Ex::ArrayLength(expr) => {
self.expressions_used.insert(expr);
}
Ex::AtomicResult { ty, comparison: _ }
| Ex::WorkGroupUniformLoadResult { ty }
| Ex::SubgroupOperationResult { ty } => {
self.types_used.insert(ty);
}
Ex::RayQueryGetIntersection {
query,
committed: _,
} => {
self.expressions_used.insert(query);
self.expressions_used.insert_iter(depth_ref);
}
Ex::ImageLoad {
image,
coordinate,
array_index,
sample,
level,
} => {
self.expressions_used.insert(image);
self.expressions_used.insert(coordinate);
self.expressions_used.insert_iter(array_index);
self.expressions_used.insert_iter(sample);
self.expressions_used.insert_iter(level);
}
Ex::ImageQuery { image, ref query } => {
self.expressions_used.insert(image);
use crate::ImageQuery as Iq;
match *query {
Iq::Size { level } => self.expressions_used.insert_iter(level),
Iq::NumLevels | Iq::NumLayers | Iq::NumSamples => {}
}
}
Ex::Unary { op: _, expr } => {
self.expressions_used.insert(expr);
}
Ex::Binary { op: _, left, right } => {
self.expressions_used.insert_iter([left, right]);
}
Ex::Select {
condition,
accept,
reject,
} => self
.expressions_used
.insert_iter([condition, accept, reject]),
Ex::Derivative {
axis: _,
ctrl: _,
expr,
} => {
self.expressions_used.insert(expr);
}
Ex::Relational { fun: _, argument } => {
self.expressions_used.insert(argument);
}
Ex::Math {
fun: _,
arg,
arg1,
arg2,
arg3,
} => {
self.expressions_used.insert(arg);
self.expressions_used.insert_iter(arg1);
self.expressions_used.insert_iter(arg2);
self.expressions_used.insert_iter(arg3);
}
Ex::As {
expr,
kind: _,
convert: _,
} => {
self.expressions_used.insert(expr);
}
Ex::ArrayLength(expr) => {
self.expressions_used.insert(expr);
}
Ex::AtomicResult { ty, comparison: _ }
| Ex::WorkGroupUniformLoadResult { ty }
| Ex::SubgroupOperationResult { ty } => {
self.types_used.insert(ty);
}
Ex::RayQueryGetIntersection {
query,
committed: _,
} => {
self.expressions_used.insert(query);
}
}
}
}
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