From d3717e66c3906731da743d8ee1d9283bc225ea8d Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Thu, 18 Feb 2021 17:46:20 +1000
Subject: [PATCH] CPU/Recompiler: Handle self-modifying code within same block

Fixes Spyro 2 and 3 PAL with recompiler.
---
 src/core/cpu_recompiler_code_generator.cpp | 26 ++++++++++++++++++++++
 src/core/cpu_recompiler_code_generator.h   |  1 +
 2 files changed, 27 insertions(+)

diff --git a/src/core/cpu_recompiler_code_generator.cpp b/src/core/cpu_recompiler_code_generator.cpp
index b569cd52e..3ba83b682 100644
--- a/src/core/cpu_recompiler_code_generator.cpp
+++ b/src/core/cpu_recompiler_code_generator.cpp
@@ -1008,6 +1008,13 @@ void CodeGenerator::InstructionEpilogue(const CodeBlockInstruction& cbi)
   }
 }
 
+void CodeGenerator::TruncateBlockAtCurrentInstruction()
+{
+  Log_DevPrintf("Truncating block %08X at %08X", m_block->GetPC(), m_current_instruction->pc);
+  m_block_end = m_current_instruction + 1;
+  WriteNewPC(CalculatePC(), true);
+}
+
 void CodeGenerator::AddPendingCycles(bool commit)
 {
   if (m_delayed_cycles_add == 0)
@@ -1496,6 +1503,25 @@ bool CodeGenerator::Compile_Store(const CodeBlockInstruction& cbi)
   }
 
   InstructionEpilogue(cbi);
+
+  if (address_spec)
+  {
+    const CPU::Segment seg = GetSegmentForAddress(*address_spec);
+    if (seg == Segment::KUSEG || seg == Segment::KSEG0 || seg == Segment::KSEG1)
+    {
+      const PhysicalMemoryAddress phys_addr = VirtualAddressToPhysical(*address_spec);
+      const PhysicalMemoryAddress block_start = VirtualAddressToPhysical(m_block->GetPC());
+      const PhysicalMemoryAddress block_end = VirtualAddressToPhysical(
+        m_block->GetPC() + static_cast<u32>(m_block->instructions.size()) * sizeof(Instruction));
+      if (phys_addr >= block_start && phys_addr < block_end)
+      {
+        Log_WarningPrintf("Instruction %08X speculatively writes to %08X inside block %08X-%08X. Truncating block.",
+                          cbi.pc, phys_addr, block_start, block_end);
+        TruncateBlockAtCurrentInstruction();
+      }
+    }
+  }
+
   return true;
 }
 
diff --git a/src/core/cpu_recompiler_code_generator.h b/src/core/cpu_recompiler_code_generator.h
index fcd8a4d20..e6db0e7dd 100644
--- a/src/core/cpu_recompiler_code_generator.h
+++ b/src/core/cpu_recompiler_code_generator.h
@@ -196,6 +196,7 @@ private:
   void BlockEpilogue();
   void InstructionPrologue(const CodeBlockInstruction& cbi, TickCount cycles, bool force_sync = false);
   void InstructionEpilogue(const CodeBlockInstruction& cbi);
+  void TruncateBlockAtCurrentInstruction();
   void AddPendingCycles(bool commit);
 
   Value CalculatePC(u32 offset = 0);