From 615a0d7dc1d57d4f9414c82396cb3b0ec817d3e1 Mon Sep 17 00:00:00 2001
From: Karol Stasiak <karol.m.stasiak@gmail.com>
Date: Wed, 9 Sep 2020 01:46:34 +0200
Subject: [PATCH] Interrupt functions in assembly should not have prologue
 (fixes #62)

---
 .../millfork/compiler/mos/MosCompiler.scala   |  2 +-
 .../millfork/compiler/z80/Z80Compiler.scala   |  2 +-
 src/main/scala/millfork/env/Environment.scala |  1 +
 src/main/scala/millfork/env/Thing.scala       |  1 +
 .../scala/millfork/test/AssemblySuite.scala   | 45 +++++++++++++++++++
 5 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/src/main/scala/millfork/compiler/mos/MosCompiler.scala b/src/main/scala/millfork/compiler/mos/MosCompiler.scala
index 0ae186b5..1f1fe551 100644
--- a/src/main/scala/millfork/compiler/mos/MosCompiler.scala
+++ b/src/main/scala/millfork/compiler/mos/MosCompiler.scala
@@ -37,7 +37,7 @@ object MosCompiler extends AbstractCompiler[AssemblyLine] {
         List(AssemblyLine.absolute(LDA, ctx.env.get[ThingInMemory]("__sp")), AssemblyLine.implied(PHA))
       } else Nil)
 
-    val prefix = storeParamsFromRegisters ++ (if (ctx.function.interrupt) {
+    val prefix = storeParamsFromRegisters ++ (if (ctx.function.interrupt && !ctx.function.inAssembly) {
 
       if (ctx.options.flag(CompilationFlag.EmitNative65816Opcodes)) {
         if (zpRegisterSize > 0) {
diff --git a/src/main/scala/millfork/compiler/z80/Z80Compiler.scala b/src/main/scala/millfork/compiler/z80/Z80Compiler.scala
index 0c56a62f..5b3a89fc 100644
--- a/src/main/scala/millfork/compiler/z80/Z80Compiler.scala
+++ b/src/main/scala/millfork/compiler/z80/Z80Compiler.scala
@@ -68,7 +68,7 @@ object Z80Compiler extends AbstractCompiler[ZLine] {
   def preserveRegisters(ctx: CompilationContext): List[ZLine] = {
     import millfork.assembly.z80.ZOpcode._
     import ZRegister._
-    if (ctx.function.interrupt) {
+    if (ctx.function.interrupt && !ctx.function.inAssembly) {
       if (ctx.options.flag(CompilationFlag.EmitZ80Opcodes)) {
         if (ctx.options.flag(CompilationFlag.UseShadowRegistersForInterrupts)) {
           List(
diff --git a/src/main/scala/millfork/env/Environment.scala b/src/main/scala/millfork/env/Environment.scala
index 418f2df8..e7fb1ed8 100644
--- a/src/main/scala/millfork/env/Environment.scala
+++ b/src/main/scala/millfork/env/Environment.scala
@@ -1378,6 +1378,7 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
             hasElidedReturnVariable = hasElidedReturnVariable,
             interrupt = stmt.interrupt,
             kernalInterrupt = stmt.kernalInterrupt,
+            inAssembly = stmt.assembly,
             reentrant = stmt.reentrant,
             isConstPure = stmt.constPure,
             position = stmt.position,
diff --git a/src/main/scala/millfork/env/Thing.scala b/src/main/scala/millfork/env/Thing.scala
index 07362b93..6f5fcffd 100644
--- a/src/main/scala/millfork/env/Thing.scala
+++ b/src/main/scala/millfork/env/Thing.scala
@@ -481,6 +481,7 @@ case class NormalFunction(name: String,
                           hasElidedReturnVariable: Boolean,
                           interrupt: Boolean,
                           kernalInterrupt: Boolean,
+                          inAssembly: Boolean,
                           isConstPure: Boolean,
                           reentrant: Boolean,
                           position: Option[Position],
diff --git a/src/test/scala/millfork/test/AssemblySuite.scala b/src/test/scala/millfork/test/AssemblySuite.scala
index d388db95..df934f0c 100644
--- a/src/test/scala/millfork/test/AssemblySuite.scala
+++ b/src/test/scala/millfork/test/AssemblySuite.scala
@@ -460,4 +460,49 @@ class AssemblySuite extends FunSuite with Matchers with AppendedClues {
     m.readByte(0xc001) should equal(1)
     m.readByte(0xc002) should equal(2)
   }
+
+  test("Interrupt functions in assembly should not have prologue (6502)") {
+    val m = EmuUnoptimizedRun(
+      """
+        |byte output @$c000
+        |noinline interrupt asm void i() {
+        |  nop
+        |  rti
+        |}
+        |void main() {
+        |   output = pointer(i.addr)[0]
+        |}
+        |""".stripMargin)
+    m.readByte(0xc000) should equal(0xea)
+  }
+
+  test("Interrupt functions in assembly should not have prologue (Z80)") {
+    val m = EmuUnoptimizedZ80Run(
+      """
+        |byte output @$c000
+        |noinline interrupt asm void i() {
+        |  nop
+        |  reti
+        |}
+        |void main() {
+        |   output = pointer(i.addr)[0]
+        |}
+        |""".stripMargin)
+    m.readByte(0xc000) should equal(0)
+  }
+
+  test("Interrupt functions in assembly should not have prologue (M6809)") {
+    val m = EmuUnoptimizedM6809Run(
+      """
+        |byte output @$c000
+        |noinline interrupt asm void i() {
+        |  nop
+        |  rti
+        |}
+        |void main() {
+        |   output = pointer(i.addr)[0]
+        |}
+        |""".stripMargin)
+    m.readByte(0xc000) should equal(0x12)
+  }
 }