From 7476baced6bb1b673402f664611a381b3e5866cc Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Fri, 17 May 2024 22:25:02 +1000
Subject: [PATCH] CPU/PGXP: Track valid Z for lower/upper halves of 32-bit
 values

Dragon Valor writes both lower and upper halfwords separately from
non-valid-Z values. The Z needs to be cleared out.
---
 src/core/cpu_pgxp.cpp | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/core/cpu_pgxp.cpp b/src/core/cpu_pgxp.cpp
index d1c0d41eb..e3679ea84 100644
--- a/src/core/cpu_pgxp.cpp
+++ b/src/core/cpu_pgxp.cpp
@@ -46,7 +46,9 @@ enum : u32
   VALID_X = (1u << 0),
   VALID_Y = (1u << 1),
   VALID_Z = (1u << 2),
-  VALID_TAINTED_Z = (1u << 31),
+  VALID_LOWZ = (1u << 16),      // Valid Z from the low part of a 32-bit value.
+  VALID_HIGHZ = (1u << 17),     // Valid Z from the high part of a 32-bit value.
+  VALID_TAINTED_Z = (1u << 31), // X/Y has been changed, Z may not be accurate.
 
   VALID_XY = (VALID_X | VALID_Y),
   VALID_XYZ = (VALID_X | VALID_Y | VALID_Z),
@@ -338,7 +340,10 @@ ALWAYS_INLINE_RELEASE void CPU::PGXP::WriteMem(const PGXP_value* value, u32 addr
   PGXP_value* pMem = GetPtr(addr);
 
   if (pMem)
+  {
     *pMem = *value;
+    pMem->flags |= VALID_LOWZ | VALID_HIGHZ;
+  }
 }
 
 ALWAYS_INLINE_RELEASE void CPU::PGXP::WriteMem16(const PGXP_value* src, u32 addr)
@@ -368,6 +373,13 @@ ALWAYS_INLINE_RELEASE void CPU::PGXP::WriteMem16(const PGXP_value* src, u32 addr
   {
     dest->z = src->z;
     dest->SetValid(COMP_Z);
+    dest->flags |= hiword ? VALID_HIGHZ : VALID_LOWZ;
+  }
+  else
+  {
+    dest->flags &= hiword ? ~VALID_HIGHZ : ~VALID_LOWZ;
+    if (dest->flags & VALID_Z && !(dest->flags & (VALID_HIGHZ | VALID_LOWZ)))
+      dest->flags &= ~VALID_Z;
   }
 }