From 9e6970de62a6955c8ec478d1582c8c6e2bbcccb7 Mon Sep 17 00:00:00 2001
From: Guy C <gc1523@ic.ac.uk>
Date: Thu, 27 Feb 2025 19:55:35 +0000
Subject: [PATCH] feat: implements overflow runtime error handling

---
 src/main/wacc/backend/RuntimeErrors.scala |  5 +++++
 src/main/wacc/backend/asmGenerator.scala  | 20 ++++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/main/wacc/backend/RuntimeErrors.scala b/src/main/wacc/backend/RuntimeErrors.scala
index d5df01c..06062ad 100644
--- a/src/main/wacc/backend/RuntimeErrors.scala
+++ b/src/main/wacc/backend/RuntimeErrors.scala
@@ -27,4 +27,9 @@ object RuntimeErrors {
     "fatal error: null pair dereferenced or freed",
     ".L._errNullPtr"
   )
+  val overflowError = RuntimeError(
+    ".L._errOverflow_str0",
+    "fatal error: integer overflow or underflow occurred",
+    ".L._errOverflow"
+  )
 }
diff --git a/src/main/wacc/backend/asmGenerator.scala b/src/main/wacc/backend/asmGenerator.scala
index 38ed7a5..411d02e 100644
--- a/src/main/wacc/backend/asmGenerator.scala
+++ b/src/main/wacc/backend/asmGenerator.scala
@@ -66,6 +66,7 @@ object asmGenerator {
     } ++ zeroDivError.stringDef
       ++ badChrError.stringDef
       ++ nullPtrError.stringDef // TODO COLLATE TO ONE LIST INSTANCE
+      ++ overflowError.stringDef
 
     Chain(
       Directive.IntelSyntax,
@@ -186,7 +187,7 @@ object asmGenerator {
       stackAlign,
       Load(RDI, IndexAddress(RIP, LabelArg(badChrError.strLabel))),
       assemblyIR.Call(CLibFunc.PrintF),
-      Move(RDI, ImmediateVal(-1)),
+      Move(RDI, ImmediateVal(255)),
       assemblyIR.Call(CLibFunc.Exit)
     )
 
@@ -199,6 +200,15 @@ object asmGenerator {
       assemblyIR.Call(CLibFunc.Exit)
     )
 
+    chain ++= Chain(
+      LabelDef(overflowError.errLabel),
+      stackAlign,
+      Load(RDI, IndexAddress(RIP, LabelArg(overflowError.strLabel))),
+      assemblyIR.Call(CLibFunc.PrintF),
+      Move(RDI, ImmediateVal(255)),
+      assemblyIR.Call(CLibFunc.Exit)
+    )
+
     chain
   }
 
@@ -345,7 +355,11 @@ object asmGenerator {
             chain += Move(EAX, MemLocation(RAX, D32))
             chain += stack.push(D32, RAX)
           case UnaryOperator.Negate =>
-            chain += Negate(stack.head)
+            chain += Xor(EAX, EAX)
+            chain += Subtract(EAX, stack.head)
+            chain += Jump(LabelArg(overflowError.errLabel), Cond.Overflow)
+            chain += stack.drop()
+            chain += stack.push(Q64, RAX)
           case UnaryOperator.Not =>
             chain += Xor(stack.head, ImmediateVal(1))
         }
@@ -359,12 +373,14 @@ object asmGenerator {
         op match {
           case BinaryOperator.Add =>
             chain += Add(stack.head, destX)
+            chain += Jump(LabelArg(overflowError.errLabel), Cond.Overflow)
           case BinaryOperator.Sub =>
             chain += Subtract(destX, stack.head)
             chain += stack.drop()
             chain += stack.push(destX.size, RAX)
           case BinaryOperator.Mul =>
             chain += Multiply(destX, stack.head)
+            chain += Jump(LabelArg(overflowError.errLabel), Cond.Overflow)
             chain += stack.drop()
             chain += stack.push(destX.size, RAX)