CPU/Recompiler: Create block links for self-looping blocks

This way invalidation will rewrite the jump back to the compiler.
Otherwise a SMC block can end up looping itself indefinitely.

Might help with Spyro 2/3. I can't seem to make them crash anymore.

src/core/cpu_code_cache.cpp

@@ -1421,6 +1421,22 @@ const void* CPU::CodeCache::CreateBlockLink(Block* block, void* code, u32 newpc)
   return dst;
 }
 
+const void* CPU::CodeCache::CreateSelfBlockLink(Block* block, void* code, const void* block_start)
+{
+  const void* dst = g_dispatcher;
+  if (g_settings.cpu_recompiler_block_linking)
+  {
+    dst = block_start;
+
+    BlockLinkMap::iterator iter = s_block_links.emplace(block->pc, code);
+    DebugAssert(block->num_exit_links < MAX_BLOCK_EXIT_LINKS);
+    block->exit_links[block->num_exit_links++] = iter;
+  }
+
+  DEBUG_LOG("Self linking {} with dst pc {:08X} to {}", code, block->pc, dst);
+  return dst;
+}
+
 void CPU::CodeCache::BacklinkBlocks(u32 pc, const void* dst)
 {
   if (!g_settings.cpu_recompiler_block_linking)

src/core/cpu_code_cache_private.h

@@ -239,6 +239,7 @@ const void* GetInterpretUncachedBlockFunction();
 void CompileOrRevalidateBlock(u32 start_pc);
 void DiscardAndRecompileBlock(u32 start_pc);
 const void* CreateBlockLink(Block* from_block, void* code, u32 newpc);
+const void* CreateSelfBlockLink(Block* block, void* code, const void* block_start);
 
 void AddLoadStoreInfo(void* code_address, u32 code_size, u32 guest_pc, const void* thunk_address);
 void AddLoadStoreInfo(void* code_address, u32 code_size, u32 guest_pc, u32 guest_block, TickCount cycles,

src/core/cpu_recompiler_arm32.cpp

@@ -741,17 +741,11 @@ void CPU::ARM32Recompiler::EndAndLinkBlock(const std::optional<u32>& newpc, bool
   }
   else
   {
-    if (newpc.value() == m_block->pc)
-    {
-      // Special case: ourselves! No need to backlink then.
-      DEBUG_LOG("Linking block at {:08X} to self", m_block->pc);
-      armEmitJmp(armAsm, armAsm->GetBuffer()->GetStartAddress<const void*>(), true);
-    }
-    else
-    {
-      const void* target = CodeCache::CreateBlockLink(m_block, armAsm->GetCursorAddress<void*>(), newpc.value());
-      armEmitJmp(armAsm, target, true);
-    }
+    const void* target = (newpc.value() == m_block->pc) ?
+                           CodeCache::CreateSelfBlockLink(m_block, armAsm->GetCursorAddress<void*>(),
+                                                          armAsm->GetBuffer()->GetStartAddress<const void*>()) :
+                           CodeCache::CreateBlockLink(m_block, armAsm->GetCursorAddress<void*>(), newpc.value());
+    armEmitJmp(armAsm, target, true);
   }
 }
 

src/core/cpu_recompiler_arm64.cpp

@@ -901,17 +901,11 @@ void CPU::ARM64Recompiler::EndAndLinkBlock(const std::optional<u32>& newpc, bool
   }
   else
   {
-    if (newpc.value() == m_block->pc)
-    {
-      // Special case: ourselves! No need to backlink then.
-      DEBUG_LOG("Linking block at {:08X} to self", m_block->pc);
-      armEmitJmp(armAsm, armAsm->GetBuffer()->GetStartAddress<const void*>(), true);
-    }
-    else
-    {
-      const void* target = CodeCache::CreateBlockLink(m_block, armAsm->GetCursorAddress<void*>(), newpc.value());
-      armEmitJmp(armAsm, target, true);
-    }
+    const void* target = (newpc.value() == m_block->pc) ?
+                           CodeCache::CreateSelfBlockLink(m_block, armAsm->GetCursorAddress<void*>(),
+                                                          armAsm->GetBuffer()->GetStartAddress<const void*>()) :
+                           CodeCache::CreateBlockLink(m_block, armAsm->GetCursorAddress<void*>(), newpc.value());
+    armEmitJmp(armAsm, target, true);
   }
 }
 

src/core/cpu_recompiler_riscv64.cpp

@@ -66,7 +66,7 @@ using namespace biscuit;
 RISCV64Recompiler s_instance;
 Recompiler* g_compiler = &s_instance;
 
-} // namespace CPU::Recompiler
+} // namespace CPU
 
 bool rvIsCallerSavedRegister(u32 id)
 {
@@ -150,7 +150,8 @@ void rvEmitFarLoad(biscuit::Assembler* rvAsm, const biscuit::GPR& reg, const voi
     rvAsm->LWU(reg, lo, reg);
 }
 
-[[maybe_unused]] void rvEmitFarStore(biscuit::Assembler* rvAsm, const biscuit::GPR& reg, const void* addr, const biscuit::GPR& tempreg)
+[[maybe_unused]] void rvEmitFarStore(biscuit::Assembler* rvAsm, const biscuit::GPR& reg, const void* addr,
+                                     const biscuit::GPR& tempreg)
 {
   const auto [hi, lo] = rvGetAddressImmediates(rvAsm->GetCursorPointer(), addr);
   rvAsm->AUIPC(tempreg, hi);
@@ -697,17 +698,11 @@ void CPU::RISCV64Recompiler::EndAndLinkBlock(const std::optional<u32>& newpc, bo
   }
   else
   {
-    if (newpc.value() == m_block->pc)
-    {
-      // Special case: ourselves! No need to backlink then.
-      DEBUG_LOG("Linking block at {:08X} to self", m_block->pc);
-      rvEmitJmp(rvAsm, rvAsm->GetBufferPointer(0));
-    }
-    else
-    {
-      const void* target = CreateBlockLink(m_block, rvAsm->GetCursorPointer(), newpc.value());
-      rvEmitJmp(rvAsm, target);
-    }
+    const void* target =
+      (newpc.value() == m_block->pc) ?
+        CodeCache::CreateSelfBlockLink(m_block, rvAsm->GetCursorPointer(), rvAsm->GetBufferPointer(0)) :
+        CodeCache::CreateBlockLink(m_block, rvAsm->GetCursorPointer(), newpc.value());
+    rvEmitJmp(rvAsm, target);
   }
 }
 

src/core/cpu_recompiler_x64.cpp

@@ -629,17 +629,10 @@ void CPU::X64Recompiler::EndAndLinkBlock(const std::optional<u32>& newpc, bool d
   }
   else
   {
-    if (newpc.value() == m_block->pc)
-    {
-      // Special case: ourselves! No need to backlink then.
-      DEBUG_LOG("Linking block at {:08X} to self", m_block->pc);
-      cg->jmp(cg->getCode());
-    }
-    else
-    {
-      const void* target = CodeCache::CreateBlockLink(m_block, cg->getCurr<void*>(), newpc.value());
-      cg->jmp(target, CodeGenerator::T_NEAR);
-    }
+    const void* target = (newpc.value() == m_block->pc) ?
+                           CodeCache::CreateSelfBlockLink(m_block, cg->getCurr<void*>(), cg->getCode()) :
+                           CodeCache::CreateBlockLink(m_block, cg->getCurr<void*>(), newpc.value());
+    cg->jmp(target, CodeGenerator::T_NEAR);
   }
 }