fuzzbug fix

src/backend/final.rs

@@ -155,12 +155,7 @@ pub fn produce_func_wasm(f: &FunctionBody, body: &SerializedBody, locations: &Lo
     wasm.locals
         .extend(locations.new_locals.iter().map(|ty| ty_to_valty(*ty)));
 
-    let mut next_delete = 0;
-    for (index, operator) in body.operators.iter().enumerate() {
-        if next_delete < locations.delete.len() && locations.delete[next_delete] == index {
-            next_delete += 1;
-            continue;
-        }
+    for operator in &body.operators {
         wasm.translate(operator, locations);
     }
 

src/backend/locations.rs

@@ -9,7 +9,6 @@ use super::{SerializedBody, SerializedOperator};
 #[derive(Debug)]
 pub struct Locations {
     pub locations: FxHashMap<(Value, usize), LocalId>,
-    pub delete: Vec<usize>,
     pub new_locals: Vec<wasmparser::Type>,
 }
 
@@ -42,7 +41,6 @@ impl Locations {
     pub fn compute(f: &FunctionBody, body: &SerializedBody) -> Locations {
         let mut locations = Locations {
             locations: FxHashMap::default(),
-            delete: vec![],
             new_locals: vec![],
         };
         let mut allocator = Allocator {
@@ -54,7 +52,7 @@ impl Locations {
             ends: vec![],
         };
 
-        allocator.compute_spans_and_deleted_ops(&body.operators[..]);
+        allocator.compute_spans(&body.operators[..]);
 
         locations
     }
@@ -73,6 +71,14 @@ impl<'a> Allocator<'a> {
             },
         );
 
+        log::trace!(
+            "handle_op: at location {} op {:?} reads {:?} writes {:?}",
+            location,
+            op,
+            reads,
+            writes
+        );
+
         for (value, index) in reads {
             let span = match self.spans.get_mut(&(value, index)) {
                 Some(span) => span,
@@ -81,64 +87,24 @@ impl<'a> Allocator<'a> {
                 }
             };
             span.end = location + 1;
+            log::trace!(" -> span for {}: {:?}", value, span);
         }
 
         for (value, index) in writes {
-            self.spans
-                .entry((value, index))
-                .or_insert(ValueSpan {
+            let span = self.spans.entry((value, index)).or_insert(ValueSpan {
                 value,
                 multi_value_index: index,
                 start: location,
                 end: location + 1,
-                })
-                .end = location + 1;
+            });
+            span.end = location + 1;
+            log::trace!(" -> span for {}: {:?}", value, span);
         }
     }
 
-    fn compute_spans_and_deleted_ops(&mut self, operators: &[SerializedOperator]) {
-        // Delete runs of Set(A), Set(B), Get(B), Get(A): these are
-        // stack-neutral sequences.
-        let mut start = None;
-        let mut current_run = vec![];
+    fn compute_spans(&mut self, operators: &[SerializedOperator]) {
+        // For each operator, get the reads and writes and construct spans.
         for (index, operator) in operators.iter().enumerate() {
-            match operator {
-                &SerializedOperator::Set(..) if start.is_none() => {
-                    start = Some(index);
-                    current_run.push(operator.clone());
-                }
-                &SerializedOperator::Set(..) => {
-                    current_run.push(operator.clone());
-                }
-                &SerializedOperator::Get(v, i)
-                    if start.is_some()
-                        && current_run.last() == Some(&SerializedOperator::Set(v, i)) =>
-                {
-                    current_run.pop();
-                    if current_run.is_empty() {
-                        for i in start.unwrap()..=index {
-                            self.locations.delete.push(i);
-                        }
-                        start = None;
-                    }
-                }
-                _ => {
-                    current_run.clear();
-                    start = None;
-                }
-            }
-        }
-
-        // For each non-deleted operator, get the reads and writes and construct spans.
-        let mut next_delete = 0;
-        for (index, operator) in operators.iter().enumerate() {
-            if next_delete < self.locations.delete.len()
-                && self.locations.delete[next_delete] == index
-            {
-                next_delete += 1;
-                continue;
-            }
-
             self.handle_op(index, operator);
         }
 

src/backend/serialize.rs

@@ -400,6 +400,7 @@ impl<'a> SerializedBodyContext<'a> {
 
         // Now push the args in reverse order.
         for &arg in operands.iter().rev() {
+            let arg = self.f.resolve_alias(arg);
             match &self.f.values[arg.index()] {
                 &ValueDef::Operator(op, ..) => {
                     if op_rematerialize(&op) {

src/backend/use_count.rs

@@ -25,6 +25,7 @@ impl UseCountAnalysis {
             for &value in &f.blocks[block].insts {
                 if value != Value::undef() {
                     let value = f.resolve_alias(value);
+                    counts.add(value);
                     if workqueue_set.insert(value) {
                         workqueue.push_back(value);
                     }
@@ -34,6 +35,7 @@ impl UseCountAnalysis {
             f.blocks[block].terminator.visit_uses(|value| {
                 if value != Value::undef() {
                     let value = f.resolve_alias(value);
+                    counts.add(value);
                     if workqueue_set.insert(value) {
                         workqueue.push_back(value);
                     }
@@ -42,7 +44,6 @@ impl UseCountAnalysis {
 
             while let Some(value) = workqueue.pop_front() {
                 workqueue_set.remove(&value);
-                counts.add(value);
                 match &f.values[value.index()] {
                     &ValueDef::Alias(..) | &ValueDef::Arg(..) | &ValueDef::BlockParam(..) => {}
                     &ValueDef::Operator(_op, ref args) => {
@@ -51,7 +52,8 @@ impl UseCountAnalysis {
                                 continue;
                             }
                             let arg = f.resolve_alias(arg);
-                            if counts.use_count[arg.index()] == 0 {
+                            counts.add(arg);
+                            if counts.use_count[arg.index()] == 1 {
                                 if workqueue_set.insert(arg) {
                                     workqueue.push_back(arg);
                                 }
@@ -63,7 +65,8 @@ impl UseCountAnalysis {
                             continue;
                         }
                         let value = f.resolve_alias(value);
-                        if counts.use_count[value.index()] == 0 {
+                        counts.add(value);
+                        if counts.use_count[value.index()] == 1 {
                             if workqueue_set.insert(value) {
                                 workqueue.push_back(value);
                             }