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rendergraph: barriers against write-after-read

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Janis 2025-01-05 16:10:30 +01:00
parent fdfc74c668
commit 260275d694
1 changed files with 18 additions and 3 deletions
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21
crates/renderer/src/render_graph.rs
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@ -305,8 +305,6 @@ impl RenderGraph {
} }
} }
let mut dag = petgraph::stable_graph::StableDiGraph::new();
#[derive(Debug, Clone, Copy)] #[derive(Debug, Clone, Copy)]
enum PassNode { enum PassNode {
First, First,
@ -314,13 +312,23 @@ impl RenderGraph {
Last, Last,
} }
let mut dag = petgraph::stable_graph::StableDiGraph::new();
let root = dag.add_node(PassNode::First); let root = dag.add_node(PassNode::First);
let mut last_write = self let mut last_write: BTreeMap<GraphResourceId, (NodeIndex, Access)> = self
.resources .resources
.keys() .keys()
.filter_map(|id| self.accesses.get(id).map(|access| (*id, (root, *access)))) .filter_map(|id| self.accesses.get(id).map(|access| (*id, (root, *access))))
.collect::<BTreeMap<_, _>>(); .collect::<BTreeMap<_, _>>();
let mut last_read: BTreeMap<GraphResourceId, (NodeIndex, Access)> = BTreeMap::new();
// TODO: rewrite finding edges properly.
// finding out if this graph is cyclical is actually non-trivial
// some pass might require both a read of a resource 1, and a read of a resource 2, where 2 is the product of another pass writing to resource 1.
// this could be resolved by copying resource 1 before the write pass.
// tl;dr: write-after-read makes this all more complicated
// insert edges between write->read edges of 2 passes // insert edges between write->read edges of 2 passes
for (i, pass) in self.pass_descs.iter().enumerate() { for (i, pass) in self.pass_descs.iter().enumerate() {
let node = dag.add_node(PassNode::Pass(i)); let node = dag.add_node(PassNode::Pass(i));
@ -341,6 +349,7 @@ impl RenderGraph {
tracing::trace!("adding edge between {other:?} and {node:?} for {rid:?} with ({before:?} -> {after:?})"); tracing::trace!("adding edge between {other:?} and {node:?} for {rid:?} with ({before:?} -> {after:?})");
dag.add_edge(other, node, (rid, (before, after))); dag.add_edge(other, node, (rid, (before, after)));
} }
last_read.insert(rid, (node, after));
} }
let mut write_accesses = BTreeMap::new(); let mut write_accesses = BTreeMap::new();
@ -356,6 +365,12 @@ impl RenderGraph {
for (rid, after) in write_accesses { for (rid, after) in write_accesses {
last_write.insert(rid, (node, after)); last_write.insert(rid, (node, after));
if let Some(&(other, read)) = last_read.get(&rid)
&& other != node
{
tracing::trace!("adding edge between {other:?} and {node:?} for {rid:?} with ({read:?} -> {after:?}) (WaR)");
dag.add_edge(other, node, (rid, (read, after)));
}
} }
} }