fixed the unreachable functions deleting branches

Signed-off-by: Jakub Doka <jakub.doka2@gmail.com>

bytecode/src/lib.rs

@@ -254,8 +254,7 @@ pub fn disasm<'a>(
                         || global_offset > off + len
                         || prev
                             .get(global_offset as usize)
-                            .map_or(true, |&b| instr_from_byte(b).is_err())
-                        || prev[global_offset as usize] == 0;
+                            .map_or(true, |&b| instr_from_byte(b).is_err());
                     has_oob |= local_has_oob;
                     let label = labels.get(&global_offset).unwrap();
                     if local_has_oob {

lang/README.md

@@ -662,10 +662,13 @@ main := fn(): uint {
 
 #### die
 ```hb
+
+fun := fn(): never die
+
 main := fn(): never {
 	// simply emmits 'un' instruction that immediately terminates the execution
 	// the expresion has similar properties to 'return' but does not accept a value
-	die
+	fun()
 }
 ```
 

lang/src/backend/hbvm/regalloc.rs

@@ -23,7 +23,7 @@ impl HbvmBackend {
         tys: &Types,
         files: &EntSlice<Module, parser::Ast>,
     ) -> (usize, bool) {
-        let tail = Function::build(nodes, tys, &mut self.ralloc, sig);
+        let tail = FunctionBuilder::build(nodes, tys, &mut self.ralloc, sig);
 
         let strip_load = |value| match nodes[value].kind {
             Kind::Load { .. } if nodes[value].ty.loc(tys) == Loc::Stack => nodes[value].inputs[1],
@@ -392,8 +392,9 @@ impl HbvmBackend {
                             todo!("unhandled operator: {op}");
                         }
                     }
-                    Kind::Call { args, func } => {
+                    Kind::Call { args, func, .. } => {
                         let (ret, mut parama) = tys.parama(node.ty);
+                        debug_assert!(node.ty != ty::Id::NEVER || ret.is_none());
                         if let Some(PLoc::Ref(r, ..)) = ret {
                             self.emit(instrs::cp(r, atr(*node.inputs.last().unwrap())))
                         }
@@ -530,7 +531,7 @@ impl HbvmBackend {
     }
 }
 
-struct Function<'a> {
+struct FunctionBuilder<'a> {
     sig: Sig,
     tail: bool,
     nodes: &'a Nodes,
@@ -538,7 +539,7 @@ struct Function<'a> {
     func: &'a mut Res,
 }
 
-impl core::fmt::Debug for Function<'_> {
+impl core::fmt::Debug for FunctionBuilder<'_> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         for block in &self.func.blocks {
             writeln!(f, "{:?}", self.nodes[block.entry].kind)?;
@@ -551,7 +552,7 @@ impl core::fmt::Debug for Function<'_> {
     }
 }
 
-impl<'a> Function<'a> {
+impl<'a> FunctionBuilder<'a> {
     fn build(nodes: &'a Nodes, tys: &'a Types, func: &'a mut Res, sig: Sig) -> bool {
         func.blocks.clear();
         func.instrs.clear();
@@ -670,11 +671,14 @@ impl<'a> Function<'a> {
                     self.emit_node(o);
                 }
             }
-            Kind::Call { func, .. } => {
+            Kind::Call { func, unreachable, .. } => {
                 self.tail &= func == ty::Func::ECA;
 
+                if unreachable {
+                    self.close_block(nid);
+                    self.emit_node(node.outputs[0]);
+                } else {
                     self.add_instr(nid);
-
                     for &o in node.outputs.iter().rev() {
                         if self.nodes[o].inputs[0] == nid
                             || (matches!(self.nodes[o].kind, Kind::Loop | Kind::Region)
@@ -684,6 +688,7 @@ impl<'a> Function<'a> {
                         }
                     }
                 }
+            }
             Kind::CInt { value: 0 } if self.nodes.is_hard_zero(nid) => {}
             Kind::CInt { .. }
             | Kind::BinOp { .. }

lang/src/fs.rs

@@ -177,8 +177,9 @@ pub fn run_compiler(
 
         if options.dump_asm {
             let mut disasm = String::new();
-            codegen.disasm(&mut disasm, out).map_err(|e| io::Error::other(e.to_string()))?;
+            let err = codegen.disasm(&mut disasm, out).map_err(|e| io::Error::other(e.to_string()));
             *out = disasm.into_bytes();
+            err?
         }
     }
 

lang/src/nodes.rs

@@ -97,6 +97,7 @@ impl Nodes {
                     debug_assert_ne!(next, 0);
                     if matches!(self[cursor].kind, Kind::Then | Kind::Else) {
                         debug_assert_eq!(self[next].kind, Kind::If);
+                        debug_assert_eq!(self[next].ty, ty::Id::VOID);
                         let other = self[next].outputs[(self[next].outputs[0] == cursor) as usize];
                         self[other].loop_depth.set(depth - 1);
                     }
@@ -1714,7 +1715,7 @@ impl Nodes {
             Kind::BinOp { op } | Kind::UnOp { op } => {
                 write!(out, "{:>4}:      ", op.name())
             }
-            Kind::Call { func, args: _ } => {
+            Kind::Call { func, args: _, unreachable: _ } => {
                 write!(out, "call: {func} {}  ", self[node].depth.get())
             }
             Kind::Global { global } => write!(out, "glob: {global:<5}"),
@@ -2109,6 +2110,7 @@ pub enum Kind {
     },
     // [ctrl, ...args]
     Call {
+        unreachable: bool,
         func: ty::Func,
         args: ty::Tuple,
     },
@@ -2163,6 +2165,7 @@ impl Kind {
 
     fn ends_basic_block(&self) -> bool {
         matches!(self, Self::Return { .. } | Self::If | Self::End | Self::Die)
+            || matches!(self, Kind::Call { unreachable: true, .. })
     }
 
     pub fn starts_basic_block(&self) -> bool {

lang/src/son.rs

@@ -1516,7 +1516,11 @@ impl<'a> Codegen<'a> {
 
                 inps[0] = self.ci.ctrl.get();
                 self.ci.ctrl.set(
-                    self.ci.nodes.new_node_nop(ty, Kind::Call { func: ty::Func::ECA, args }, inps),
+                    self.ci.nodes.new_node_nop(
+                        ty,
+                        Kind::Call { func: ty::Func::ECA, args, unreachable: false },
+                        inps,
+                    ),
                     &mut self.ci.nodes,
                 );
 
@@ -2656,13 +2660,19 @@ impl<'a> Codegen<'a> {
 
             inps[0] = self.ci.ctrl.get();
             self.ci.ctrl.set(
-                self.ci.nodes.new_node_nop(sig.ret, Kind::Call { func: fu, args: sig.args }, inps),
+                self.ci.nodes.new_node_nop(
+                    sig.ret,
+                    Kind::Call { func: fu, args: sig.args, unreachable: sig.ret == ty::Id::NEVER },
+                    inps,
+                ),
                 &mut self.ci.nodes,
             );
 
             self.add_clobber_stores(clobbered_aliases);
 
             if sig.ret == ty::Id::NEVER {
+                self.ci.nodes.bind(self.ci.ctrl.get(), NEVER);
+                self.ci.ctrl.set(NEVER, &mut self.ci.nodes);
                 return None;
             }