Jit64: Check downcount at block exit, not block entry

2 files changed, 26 insertions, 20 deletions

diff --git a/Source/Core/Core/PowerPC/Jit64/Jit.cpp b/Source/Core/Core/PowerPC/Jit64/Jit.cpp
index 2cdad6e54d..b2e893e2c0 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit.cpp
@@ -442,21 +442,36 @@ void Jit64::JustWriteExit(u32 destination, bool bl, u32 after)
   JitBlock::LinkData linkData;
   linkData.exitAddress = destination;
   linkData.linkStatus = false;
+  linkData.call = bl;
 
   MOV(32, PPCSTATE(pc), Imm32(destination));
-  linkData.exitPtrs = GetWritableCodePtr();
-  if (bl)
-    CALL(asm_routines.dispatcher);
-  else
-    JMP(asm_routines.dispatcher, true);
-
-  b->linkData.push_back(linkData);
 
+  // Perform downcount flag check, followed by the requested exit
   if (bl)
   {
+    FixupBranch do_timing = J_CC(CC_LE, true);
+    SwitchToFarCode();
+    SetJumpTarget(do_timing);
+    CALL(asm_routines.do_timing);
+    FixupBranch after_fixup = J(true);
+    SwitchToNearCode();
+
+    linkData.exitPtrs = GetWritableCodePtr();
+    CALL(asm_routines.dispatcher_no_check);
+
+    SetJumpTarget(after_fixup);
     POP(RSCRATCH);
     JustWriteExit(after, false, 0);
   }
+  else
+  {
+    J_CC(CC_LE, asm_routines.do_timing);
+
+    linkData.exitPtrs = GetWritableCodePtr();
+    JMP(asm_routines.dispatcher_no_check, true);
+  }
+
+  b->linkData.push_back(linkData);
 }
 
 void Jit64::WriteExitDestInRSCRATCH(bool bl, u32 after)
@@ -660,16 +675,7 @@ u8* Jit64::DoJit(u32 em_address, JitBlock* b, u32 nextPC)
   // TODO: Test if this or AlignCode16 make a difference from GetCodePtr
   u8* const start = AlignCode4();
   b->checkedEntry = start;
-
-  // Downcount flag check. The last block decremented downcounter, and the flag should still be
-  // available.
-  FixupBranch skip = J_CC(CC_G);
-  MOV(32, PPCSTATE(pc), Imm32(js.blockStart));
-  JMP(asm_routines.do_timing, true);  // downcount hit zero - go do_timing.
-  SetJumpTarget(skip);
-
-  u8* const normal_entry = GetWritableCodePtr();
-  b->normalEntry = normal_entry;
+  b->normalEntry = start;
 
   // Used to get a trace of the last few blocks before a crash, sometimes VERY useful
   if (ImHereDebug)
@@ -955,7 +961,7 @@ u8* Jit64::DoJit(u32 em_address, JitBlock* b, u32 nextPC)
   LogGeneratedX86(code_block.m_num_instructions, m_code_buffer, start, b);
 #endif
 
-  return normal_entry;
+  return start;
 }
 
 BitSet8 Jit64::ComputeStaticGQRs(const PPCAnalyst::CodeBlock& cb) const
diff --git a/Source/Core/Core/PowerPC/Jit64Common/BlockCache.cpp b/Source/Core/Core/PowerPC/Jit64Common/BlockCache.cpp
index 096a46f57d..e857226265 100644
--- a/Source/Core/Core/PowerPC/Jit64Common/BlockCache.cpp
+++ b/Source/Core/Core/PowerPC/Jit64Common/BlockCache.cpp
@@ -15,9 +15,9 @@ JitBlockCache::JitBlockCache(JitBase& jit) : JitBaseBlockCache{jit}
 void JitBlockCache::WriteLinkBlock(const JitBlock::LinkData& source, const JitBlock* dest)
 {
   u8* location = source.exitPtrs;
-  const u8* address = dest ? dest->checkedEntry : m_jit.GetAsmRoutines()->dispatcher;
+  const u8* address = dest ? dest->checkedEntry : m_jit.GetAsmRoutines()->dispatcher_no_check;
   Gen::XEmitter emit(location);
-  if (*location == 0xE8)
+  if (source.call)
   {
     emit.CALL(address);
   }