From 1bfac23fac8b749cdcbd0232253a57b29ec91142 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Mon, 6 Apr 2026 17:40:29 +0100
Subject: Support unreachable instruction in patio-to-cranelift

---
 patio-to-cranelift/src/codegen/mod.rs        | 16 +++++++++++++++-
 patio-to-cranelift/src/patio/flatbuffers.rs  |  7 ++++++-
 patio-to-cranelift/src/patio/instructions.rs |  3 +++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/patio-to-cranelift/src/codegen/mod.rs b/patio-to-cranelift/src/codegen/mod.rs
index 1e898123..29a8d949 100644
--- a/patio-to-cranelift/src/codegen/mod.rs
+++ b/patio-to-cranelift/src/codegen/mod.rs
@@ -20,7 +20,7 @@ use crate::{
             PatioInstruction, PatioIntAdd, PatioIntEquals, PatioIntNotEqual, PatioIntSub,
             PatioIntToBool, PatioIntToDataPtr, PatioLocalStore, PatioLoop, PatioLoopBreak,
             PatioLoopContinue, PatioMemoryLoad, PatioMemoryStore, PatioResume, PatioReturn,
-            PatioReturnVoid, PatioSwitch, PatioVarLoad, PatioVarStore,
+            PatioReturnVoid, PatioSwitch, PatioUnreachable, PatioVarLoad, PatioVarStore,
         },
         operands::{PatioLocalRef, PatioOperand},
         types::PatioType,
@@ -372,6 +372,10 @@ fn compile_instruction(instruction: &PatioInstruction, context: &mut CompilerFun
             compile_switch(switch, context);
         }
 
+        PatioInstruction::Unreachable(unreachable) => {
+            compile_unreachable(unreachable, context);
+        }
+
         PatioInstruction::VarLoad(var_load) => {
             compile_var_load(var_load, context);
         }
@@ -764,6 +768,11 @@ fn compile_switch(switch: &PatioSwitch, context: &mut CompilerFunctionContext<'_
     }
 }
 
+fn compile_unreachable(_: &PatioUnreachable, context: &mut CompilerFunctionContext<'_>) {
+    context.function_builder.ins().trap(trap_codes::UNREACHABLE);
+    context.mark_unreachable();
+}
+
 fn compile_var_load(var_load: &PatioVarLoad, context: &mut CompilerFunctionContext<'_>) {
     let cranelift_variable = context.var(&var_load.var.name);
     let cranelift_value = context.function_builder.use_var(cranelift_variable);
@@ -943,3 +952,8 @@ fn patio_operand_to_cranelift_type(
         PatioOperand::LocalRef(local_ref) => context.local_type(&local_ref.name),
     }
 }
+
+mod trap_codes {
+    pub(super) const UNREACHABLE: cranelift_codegen::ir::TrapCode =
+        cranelift_codegen::ir::TrapCode::unwrap_user(1);
+}
diff --git a/patio-to-cranelift/src/patio/flatbuffers.rs b/patio-to-cranelift/src/patio/flatbuffers.rs
index 34e0a1a1..4e391b66 100644
--- a/patio-to-cranelift/src/patio/flatbuffers.rs
+++ b/patio-to-cranelift/src/patio/flatbuffers.rs
@@ -11,7 +11,8 @@ use crate::{
             PatioInstruction, PatioIntAdd, PatioIntEquals, PatioIntNotEqual, PatioIntSub,
             PatioIntToBool, PatioIntToDataPtr, PatioLocalStore, PatioLoop, PatioLoopBreak,
             PatioLoopContinue, PatioMemoryLoad, PatioMemoryStore, PatioResume, PatioReturn,
-            PatioReturnVoid, PatioSwitch, PatioSwitchCase, PatioVarLoad, PatioVarStore,
+            PatioReturnVoid, PatioSwitch, PatioSwitchCase, PatioUnreachable, PatioVarLoad,
+            PatioVarStore,
         },
         operands::{PatioLocalRef, PatioOperand},
         types::{PatioDataLayout, PatioType},
@@ -341,6 +342,10 @@ impl From<patio_generated::patio::PatioInstruction<'_>> for PatioInstruction {
                 })
             }
 
+            patio_generated::patio::PatioInstructionValue::PatioUnreachable => {
+                Self::Unreachable(PatioUnreachable)
+            }
+
             patio_generated::patio::PatioInstructionValue::PatioVarLoad => {
                 let var_load = value.value_as_patio_var_load().unwrap();
 
diff --git a/patio-to-cranelift/src/patio/instructions.rs b/patio-to-cranelift/src/patio/instructions.rs
index e9a3824e..8d05f6a2 100644
--- a/patio-to-cranelift/src/patio/instructions.rs
+++ b/patio-to-cranelift/src/patio/instructions.rs
@@ -26,6 +26,7 @@ pub(crate) enum PatioInstruction {
     Return(PatioReturn),
     ReturnVoid(PatioReturnVoid),
     Switch(PatioSwitch),
+    Unreachable(PatioUnreachable),
     VarLoad(PatioVarLoad),
     VarStore(PatioVarStore),
 }
@@ -147,6 +148,8 @@ pub(crate) struct PatioSwitchCase {
     pub(crate) body: PatioBlock,
 }
 
+pub(crate) struct PatioUnreachable;
+
 pub(crate) struct PatioVarLoad {
     pub(crate) destination: PatioLocalRef,
     pub(crate) var: PatioLocalRef,
-- 
cgit v1.2.3