From 6fe19d8bbe295575c8a5c5d5b15b5be8beb2bc64 Mon Sep 17 00:00:00 2001
From: KallDrexx <me@mshapiro.net>
Date: Wed, 31 Dec 2025 15:24:31 -0500
Subject: [PATCH] Testrunner ignore N and V flags in bcd mode

---
 .../Compilation/InstructionConverter.cs       |  3 +++
 .../TestRunner.cs                             | 22 ++++++++++++++++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/Dotnet6502.Common/Compilation/InstructionConverter.cs b/src/Dotnet6502.Common/Compilation/InstructionConverter.cs
index 4b8a6dc..be0ed74 100644
--- a/src/Dotnet6502.Common/Compilation/InstructionConverter.cs
+++ b/src/Dotnet6502.Common/Compilation/InstructionConverter.cs
@@ -210,6 +210,9 @@ public static class InstructionConverter
 
         var setAcc = new Ir6502.Copy(result, accumulator);
 
+        // Note: I can't find reliable info on what the zero flag should be in decimal mode. 6502 test suite
+        // claims it should follow non-BCD logic, but other references state it should be zero result from BCD logic.
+        // For now I'm just going to assume it follows a zero result but will probably revisit.
         var setZeroFlag = new Ir6502.Binary(
             Ir6502.BinaryOperator.Equals,
             result,
diff --git a/src/Dotnet6502.ComprehensiveTestRunner/TestRunner.cs b/src/Dotnet6502.ComprehensiveTestRunner/TestRunner.cs
index 52f8449..76ca680 100644
--- a/src/Dotnet6502.ComprehensiveTestRunner/TestRunner.cs
+++ b/src/Dotnet6502.ComprehensiveTestRunner/TestRunner.cs
@@ -1,5 +1,6 @@
 using System.Text.Json;
 using Dotnet6502.Common.Compilation;
+using Dotnet6502.Common.Hardware;
 using NESDecompiler.Core.CPU;
 using NESDecompiler.Core.Disassembly;
 
@@ -131,10 +132,25 @@ public static class TestRunner
                     errorMessages.Add($"Y: expected {testCase.Final.Y}, actual {jit.TestHal.YRegister}");
                 }
 
-                if (jit.TestHal.ProcessorStatus != testCase.Final.P)
+                // If we are in decimal mode, we need to ignore the negative and overflow flags, as they are
+                // undefined behavior.
+                if (jit.TestHal.GetFlag(CpuStatusFlags.Decimal))
                 {
-                    hasFailure = true;
-                    errorMessages.Add($"P: expected {testCase.Final.P}, actual {jit.TestHal.ProcessorStatus}");
+                    var testValue = jit.TestHal.ProcessorStatus & 0b00111111;
+                    var expectedValue = testCase.Final.P & 0b00111111;
+                    if (testValue != expectedValue)
+                    {
+                        hasFailure = true;
+                        errorMessages.Add($"Decimal mode P: expected {expectedValue}, actual {testValue}");
+                    }
+                }
+                else
+                {
+                    if (jit.TestHal.ProcessorStatus != testCase.Final.P)
+                    {
+                        hasFailure = true;
+                        errorMessages.Add($"P: expected {testCase.Final.P}, actual {jit.TestHal.ProcessorStatus}");
+                    }
                 }
 
                 if (jit.TestHal.StackPointer != testCase.Final.S)