From a4a9b887907db1eb883346cc71f914c2b746f708 Mon Sep 17 00:00:00 2001
From: CharlieTap <charlie.tapping@deliveroo.co.uk>
Date: Thu, 30 Jan 2025 19:27:49 +0000
Subject: [PATCH] prevent boxing in throw ref

---
 .../instruction/control/ThrowRefExecutor.kt   | 19 ++++++++++---------
 .../executor/runtime/error/InvocationError.kt |  2 ++
 .../chasm/executor/runtime/ext/LongExt.kt     |  9 +++++++++
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/executor/invoker/src/commonMain/kotlin/io/github/charlietap/chasm/executor/invoker/instruction/control/ThrowRefExecutor.kt b/executor/invoker/src/commonMain/kotlin/io/github/charlietap/chasm/executor/invoker/instruction/control/ThrowRefExecutor.kt
index f3669901..e5177c6e 100644
--- a/executor/invoker/src/commonMain/kotlin/io/github/charlietap/chasm/executor/invoker/instruction/control/ThrowRefExecutor.kt
+++ b/executor/invoker/src/commonMain/kotlin/io/github/charlietap/chasm/executor/invoker/instruction/control/ThrowRefExecutor.kt
@@ -11,7 +11,8 @@ import io.github.charlietap.chasm.executor.runtime.exception.ExceptionHandler
 import io.github.charlietap.chasm.executor.runtime.exception.InvocationException
 import io.github.charlietap.chasm.executor.runtime.execution.ExecutionContext
 import io.github.charlietap.chasm.executor.runtime.ext.exception
-import io.github.charlietap.chasm.executor.runtime.ext.popReference
+import io.github.charlietap.chasm.executor.runtime.ext.isNullableReference
+import io.github.charlietap.chasm.executor.runtime.ext.toExceptionAddress
 import io.github.charlietap.chasm.executor.runtime.ext.toLong
 import io.github.charlietap.chasm.executor.runtime.instruction.ControlInstruction
 import io.github.charlietap.chasm.executor.runtime.stack.ControlStack
@@ -37,21 +38,21 @@ internal inline fun ThrowRefExecutor(
     val cstack = context.cstack
     val store = context.store
 
-    val ref = stack.popReference()
+    val ref = stack.pop()
 
-    val exceptionRef = if (ref is ReferenceValue.Null) {
+    val exceptionAddress = if (ref.isNullableReference()) {
         throw InvocationException(InvocationError.UnexpectedReferenceValue)
     } else {
-        ref as ReferenceValue.Exception
+        ref.toExceptionAddress()
     }
 
-    val instance = store.exception(exceptionRef.address)
+    val instance = store.exception(exceptionAddress)
     val address = instance.tagAddress
 
     val handler = jumpToHandlerInstruction(cstack)
 
     if (handler.instructions.isEmpty()) {
-        stack.push(ReferenceValue.Exception(exceptionRef.address).toLong())
+        stack.push(ReferenceValue.Exception(exceptionAddress).toLong())
         cstack.push(ThrowRefDispatcher(ControlInstruction.ThrowRef))
     } else {
 
@@ -83,7 +84,7 @@ internal inline fun ThrowRefExecutor(
             catchHandler is CatchHandler.CatchRef && tagMatches -> {
                 instance.fields.reverse()
                 stack.push(instance.fields)
-                stack.push(exceptionRef.toLong())
+                stack.push(ref)
                 cstack.push(
                     breakDispatcher(ControlInstruction.Br(catchHandler.labelIndex)),
                 )
@@ -94,7 +95,7 @@ internal inline fun ThrowRefExecutor(
                 )
             }
             catchHandler is CatchHandler.CatchAllRef -> {
-                stack.push(exceptionRef.toLong())
+                stack.push(ref)
                 cstack.push(
                     breakDispatcher(ControlInstruction.Br(catchHandler.labelIndex)),
                 )
@@ -105,7 +106,7 @@ internal inline fun ThrowRefExecutor(
                 cstack.push(handler)
                 val instruction = handlerDispatcher(handler)
                 cstack.push(instruction)
-                stack.push(exceptionRef.toLong())
+                stack.push(ref)
                 cstack.push(ThrowRefDispatcher(ControlInstruction.ThrowRef))
             }
         }
diff --git a/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/error/InvocationError.kt b/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/error/InvocationError.kt
index a4a554d1..a1fdd634 100644
--- a/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/error/InvocationError.kt
+++ b/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/error/InvocationError.kt
@@ -128,6 +128,8 @@ sealed interface InvocationError : ModuleTrapError {
 
     data object ReferenceValueExpected : InvocationError
 
+    data object ExceptionReferenceExpected : InvocationError
+
     data object FunctionReferenceExpected : InvocationError
 
     data object StructReferenceExpected : InvocationError
diff --git a/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/ext/LongExt.kt b/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/ext/LongExt.kt
index c74681df..7cdaee71 100644
--- a/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/ext/LongExt.kt
+++ b/executor/runtime-internal/src/commonMain/kotlin/io/github/charlietap/chasm/executor/runtime/ext/LongExt.kt
@@ -43,6 +43,15 @@ inline fun Long.toArrayAddress(): Address.Array {
     return Address.Array(address)
 }
 
+inline fun Long.toExceptionAddress(): Address.Exception {
+    val typeId = this and RV_TYPE_MASK
+    if (typeId != RV_TYPE_EXCEPTION) {
+        throw InvocationException(InvocationError.ExceptionReferenceExpected)
+    }
+    val address = (this shr RV_SHIFT_BITS).toInt()
+    return Address.Exception(address)
+}
+
 inline fun Long.toFunctionAddress(): Address.Function {
     val typeId = this and RV_TYPE_MASK
     if (typeId != RV_TYPE_FUNCTION) {