From 07c67dbef6cde2cadcdeaf2a27a70acefb34f288 Mon Sep 17 00:00:00 2001
From: Guy C <gc1523@ic.ac.uk>
Date: Wed, 26 Feb 2025 07:13:12 +0000
Subject: [PATCH] feat: add zero division error handling in asmGenerator

---
 src/main/wacc/backend/asmGenerator.scala | 33 +++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/main/wacc/backend/asmGenerator.scala b/src/main/wacc/backend/asmGenerator.scala
index a9b5fba..7212e56 100644
--- a/src/main/wacc/backend/asmGenerator.scala
+++ b/src/main/wacc/backend/asmGenerator.scala
@@ -12,6 +12,24 @@ object asmGenerator {
   import wacc.types._
   import lexer.escapedChars
 
+  abstract case class Error() {
+    def strLabel: String
+    def errStr: String
+    def errLabel: String
+
+    def stringDef: Chain[AsmLine] = Chain(
+      Directive.Int(errStr.size),
+      LabelDef(strLabel),
+      Directive.Asciz(errStr)
+    )
+  }
+  object zeroDivError extends Error {
+    // TODO: is this bad? Can we make an error case class/some other structure?
+    def strLabel = ".L._errDivZero_str0"
+    def errStr = "fatal error: division or modulo by zero"
+    def errLabel = ".L._errDivZero"
+  }
+
   val RAX = Register(RegSize.R64, RegName.AX)
   val EAX = Register(RegSize.E32, RegName.AX)
   val ESP = Register(RegSize.E32, RegName.SP)
@@ -66,7 +84,7 @@ object asmGenerator {
         LabelDef(s".L.str$i"),
         Directive.Asciz(str.escaped)
       )
-    }
+    } ++ zeroDivError.stringDef
 
     Chain(
       Directive.IntelSyntax,
@@ -135,6 +153,17 @@ object asmGenerator {
       )
     )
 
+    chain ++= Chain(
+      // TODO can this be done with a call to generateStmt?
+      // Consider other error cases -> look to generalise
+      LabelDef(zeroDivError.errLabel),
+      stack.align(),
+      Load(RDI, IndexAddress(RIP, LabelArg(zeroDivError.strLabel))),
+      assemblyIR.Call(CLibFunc.PrintF),
+      Move(RDI, ImmediateVal(-1)),
+      assemblyIR.Call(CLibFunc.Exit)
+    )
+
     chain
   }
 
@@ -254,6 +283,8 @@ object asmGenerator {
             chain += stack.push(RAX)
 
           case BinaryOperator.Div =>
+            chain += Compare(stack.head(SizeDir.Word), ImmediateVal(0))
+            chain += Jump(LabelArg(zeroDivError.errLabel), Cond.Equal)
             chain += CDQ()
             chain += Divide(stack.head(SizeDir.Word))
             chain += stack.drop()