From f4a3601d6e7f6b35c95e9a55d4134d7f571cf99a Mon Sep 17 00:00:00 2001
From: Karol Stasiak <karol.m.stasiak@gmail.com>
Date: Wed, 11 Nov 2020 00:25:39 +0100
Subject: [PATCH] 8080: Fix word negation

---
 .../scala/millfork/compiler/z80/ZBuiltIns.scala  | 16 +++++++++++++++-
 src/test/scala/millfork/test/WordMathSuite.scala | 14 ++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/main/scala/millfork/compiler/z80/ZBuiltIns.scala b/src/main/scala/millfork/compiler/z80/ZBuiltIns.scala
index 5f97647d..b316efae 100644
--- a/src/main/scala/millfork/compiler/z80/ZBuiltIns.scala
+++ b/src/main/scala/millfork/compiler/z80/ZBuiltIns.scala
@@ -279,7 +279,21 @@ object ZBuiltIns {
           ctx.env.eval(expr) match {
             case None =>
               if (result.isEmpty) {
-                ???
+                if (ctx.options.flag(CompilationFlag.EmitZ80Opcodes)) {
+                  result ++= Z80ExpressionCompiler.compileToBC(ctx, expr)
+                  result += ZLine.ldImm16(ZRegister.HL, 0)
+                  result += ZLine.register(OR, ZRegister.A)
+                  result += ZLine.registers(SBC_16, ZRegister.HL, ZRegister.BC)
+                } else {
+                  result ++= Z80ExpressionCompiler.compileToHL(ctx, expr)
+                  result += ZLine.register(DEC_16, ZRegister.HL)
+                  result += ZLine.ld8(ZRegister.A, ZRegister.H)
+                  result += ZLine.implied(CPL)
+                  result += ZLine.ld8(ZRegister.H, ZRegister.A)
+                  result += ZLine.ld8(ZRegister.A, ZRegister.L)
+                  result += ZLine.implied(CPL)
+                  result += ZLine.ld8(ZRegister.L, ZRegister.A)
+                }
               } else {
                 if (ctx.options.flag(CompilationFlag.EmitZ80Opcodes)) {
                   // TODO: optimize
diff --git a/src/test/scala/millfork/test/WordMathSuite.scala b/src/test/scala/millfork/test/WordMathSuite.scala
index 87a39463..50715be2 100644
--- a/src/test/scala/millfork/test/WordMathSuite.scala
+++ b/src/test/scala/millfork/test/WordMathSuite.scala
@@ -268,6 +268,20 @@ class WordMathSuite extends FunSuite with Matchers with AppendedClues {
     }
   }
 
+  test("Word addition 6") {
+    EmuCrossPlatformBenchmarkRun(Cpu.Sixteen, Cpu.Mos, Cpu.Z80, Cpu.Intel8080, Cpu.Intel8085, Cpu.Sharp, Cpu.Intel8086, Cpu.Motorola6809)("""
+        | byte output @$c000
+        | void main () {
+        |  signed16 p
+        |  p = f()
+        |  output = lo(-p)
+        | }
+        | noinline signed16 f() = 6
+      """.stripMargin) { m =>
+      m.readByte(0xc000) should equal((-6) & 0xff)
+    }
+  }
+
   test("Word bit ops 2") {
     EmuCrossPlatformBenchmarkRun(Cpu.Sixteen, Cpu.Mos, Cpu.Z80, Cpu.Intel8080, Cpu.Sharp, Cpu.Intel8086, Cpu.Motorola6809)("""
         | word output @$c000