Merge pull request #7287 from degasus/idle_skipping

Jit64 / JitArm64: Optimized idle skipping detection.

12 files changed, 202 insertions, 155 deletions

diff --git a/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreter.cpp b/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreter.cpp
index 81bd4b9a00..e2e4dd5a75 100644
--- a/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreter.cpp
+++ b/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreter.cpp
@@ -181,6 +181,15 @@ static bool CheckBreakpoint(u32 data)
   return false;
 }
 
+static bool CheckIdle(u32 idle_pc)
+{
+  if (PowerPC::ppcState.npc == idle_pc)
+  {
+    CoreTiming::Idle();
+  }
+  return false;
+}
+
 bool CachedInterpreter::HandleFunctionHooking(u32 address)
 {
   return HLE::ReplaceFunctionIfPossible(address, [&](u32 function, HLE::HookType type) {
@@ -242,6 +251,7 @@ void CachedInterpreter::Jit(u32 address)
       const bool check_fpu = (op.opinfo->flags & FL_USE_FPU) && !js.firstFPInstructionFound;
       const bool endblock = (op.opinfo->flags & FL_ENDBLOCK) != 0;
       const bool memcheck = (op.opinfo->flags & FL_LOADSTORE) && jo.memcheck;
+      const bool idle_loop = op.branchIsIdleLoop;
 
       if (breakpoint)
       {
@@ -261,6 +271,8 @@ void CachedInterpreter::Jit(u32 address)
       m_code.emplace_back(PPCTables::GetInterpreterOp(op.inst), op.inst);
       if (memcheck)
         m_code.emplace_back(CheckDSI, js.downcountAmount);
+      if (idle_loop)
+        m_code.emplace_back(CheckIdle, js.blockStart);
       if (endblock)
         m_code.emplace_back(EndBlock, js.downcountAmount);
     }
diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_Branch.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_Branch.cpp
index a1920b3eef..3630eb37c7 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_Branch.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_Branch.cpp
@@ -5,7 +5,6 @@
 #include "Common/Assert.h"
 #include "Common/CommonTypes.h"
 #include "Core/ConfigManager.h"
-#include "Core/CoreTiming.h"
 #include "Core/HLE/HLE.h"
 #include "Core/PowerPC/Interpreter/ExceptionUtils.h"
 #include "Core/PowerPC/Interpreter/Interpreter.h"
@@ -23,11 +22,6 @@ void Interpreter::bx(UGeckoInstruction inst)
     NPC = PC + SignExt26(inst.LI << 2);
 
   m_end_block = true;
-
-  if (NPC == PC)
-  {
-    CoreTiming::Idle();
-  }
 }
 
 // bcx - ugly, straight from PPC manual equations :)
@@ -56,24 +50,6 @@ void Interpreter::bcx(UGeckoInstruction inst)
   }
 
   m_end_block = true;
-
-  // this code trys to detect the most common idle loop:
-  // lwz r0, XXXX(r13)
-  // cmpXwi r0,0
-  // beq -8
-  if (NPC == PC - 8 && inst.hex == 0x4182fff8 /* beq */)
-  {
-    if (PowerPC::HostRead_U32(PC - 8) >> 16 == 0x800D /* lwz */)
-    {
-      u32 last_inst = PowerPC::HostRead_U32(PC - 4);
-
-      if (last_inst == 0x28000000 /* cmplwi */ ||
-          (last_inst == 0x2C000000 /* cmpwi */ && SConfig::GetInstance().bWii))
-      {
-        CoreTiming::Idle();
-      }
-    }
-  }
 }
 
 void Interpreter::bcctrx(UGeckoInstruction inst)
diff --git a/Source/Core/Core/PowerPC/Interpreter/Interpreter_Tables.cpp b/Source/Core/Core/PowerPC/Interpreter/Interpreter_Tables.cpp
index 1ff7a60c8b..c10de1092c 100644
--- a/Source/Core/Core/PowerPC/Interpreter/Interpreter_Tables.cpp
+++ b/Source/Core/Core/PowerPC/Interpreter/Interpreter_Tables.cpp
@@ -29,8 +29,8 @@ static std::array<GekkoOPTemplate, 54> primarytable =
 	{59, Interpreter::RunTable59,   {"RunTable59", OpType::Subtable, 0, 0, 0, 0, 0}},
 	{63, Interpreter::RunTable63,   {"RunTable63", OpType::Subtable, 0, 0, 0, 0, 0}},
 
-	{16, Interpreter::bcx,          {"bcx", OpType::System, FL_ENDBLOCK, 1, 0, 0, 0}},
-	{18, Interpreter::bx,           {"bx",  OpType::System, FL_ENDBLOCK, 1, 0, 0, 0}},
+	{16, Interpreter::bcx,          {"bcx", OpType::Branch, FL_ENDBLOCK, 1, 0, 0, 0}},
+	{18, Interpreter::bx,           {"bx",  OpType::Branch, FL_ENDBLOCK, 1, 0, 0, 0}},
 
 	{3,  Interpreter::twi,          {"twi", OpType::System, FL_ENDBLOCK, 1, 0, 0, 0}},
 	{17, Interpreter::sc,           {"sc",  OpType::System, FL_ENDBLOCK, 2, 0, 0, 0}},
diff --git a/Source/Core/Core/PowerPC/Jit64/Jit.cpp b/Source/Core/Core/PowerPC/Jit64/Jit.cpp
index 545047c40c..6934f66479 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit.cpp
@@ -646,6 +646,15 @@ void Jit64::WriteRfiExitDestInRSCRATCH()
   JMP(asm_routines.dispatcher, true);
 }
 
+void Jit64::WriteIdleExit(u32 destination)
+{
+  ABI_PushRegistersAndAdjustStack({}, 0);
+  ABI_CallFunction(CoreTiming::Idle);
+  ABI_PopRegistersAndAdjustStack({}, 0);
+  MOV(32, PPCSTATE(pc), Imm32(destination));
+  WriteExceptionExit();
+}
+
 void Jit64::WriteExceptionExit()
 {
   Cleanup();
diff --git a/Source/Core/Core/PowerPC/Jit64/Jit.h b/Source/Core/Core/PowerPC/Jit64/Jit.h
index 452cdbdfc6..d2baa32c8a 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit.h
+++ b/Source/Core/Core/PowerPC/Jit64/Jit.h
@@ -84,6 +84,7 @@ public:
   void WriteExceptionExit();
   void WriteExternalExceptionExit();
   void WriteRfiExitDestInRSCRATCH();
+  void WriteIdleExit(u32 destination);
   bool Cleanup();
 
   void GenerateConstantOverflow(bool overflow);
diff --git a/Source/Core/Core/PowerPC/Jit64/Jit_Branch.cpp b/Source/Core/Core/PowerPC/Jit64/Jit_Branch.cpp
index 7e0ded66c8..bd257a3977 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit_Branch.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit_Branch.cpp
@@ -87,25 +87,18 @@ void Jit64::bx(UGeckoInstruction inst)
   gpr.Flush();
   fpr.Flush();
 
-  u32 destination;
-  if (inst.AA)
-    destination = SignExt26(inst.LI << 2);
-  else
-    destination = js.compilerPC + SignExt26(inst.LI << 2);
 #ifdef ACID_TEST
   if (inst.LK)
     AND(32, PPCSTATE(cr), Imm32(~(0xFF000000)));
 #endif
-  if (destination == js.compilerPC)
+  if (js.op->branchIsIdleLoop)
   {
-    ABI_PushRegistersAndAdjustStack({}, 0);
-    ABI_CallFunction(CoreTiming::Idle);
-    ABI_PopRegistersAndAdjustStack({}, 0);
-    MOV(32, PPCSTATE(pc), Imm32(destination));
-    WriteExceptionExit();
-    return;
+    WriteIdleExit(js.op->branchTo);
+  }
+  else
+  {
+    WriteExit(js.op->branchTo, inst.LK, js.compilerPC + 4);
   }
-  WriteExit(destination, inst.LK, js.compilerPC + 4);
 }
 
 // TODO - optimize to hell and beyond
@@ -154,18 +147,20 @@ void Jit64::bcx(UGeckoInstruction inst)
     return;
   }
 
-  u32 destination;
-  if (inst.AA)
-    destination = SignExt16(inst.BD << 2);
-  else
-    destination = js.compilerPC + SignExt16(inst.BD << 2);
-
   {
     RCForkGuard gpr_guard = gpr.Fork();
     RCForkGuard fpr_guard = fpr.Fork();
     gpr.Flush();
     fpr.Flush();
-    WriteExit(destination, inst.LK, js.compilerPC + 4);
+
+    if (js.op->branchIsIdleLoop)
+    {
+      WriteIdleExit(js.op->branchTo);
+    }
+    else
+    {
+      WriteExit(js.op->branchTo, inst.LK, js.compilerPC + 4);
+    }
   }
 
   if ((inst.BO & BO_DONT_CHECK_CONDITION) == 0)
@@ -282,7 +277,15 @@ void Jit64::bclrx(UGeckoInstruction inst)
     RCForkGuard fpr_guard = fpr.Fork();
     gpr.Flush();
     fpr.Flush();
-    WriteBLRExit();
+
+    if (js.op->branchIsIdleLoop)
+    {
+      WriteIdleExit(js.op->branchTo);
+    }
+    else
+    {
+      WriteBLRExit();
+    }
   }
 
   if ((inst.BO & BO_DONT_CHECK_CONDITION) == 0)
diff --git a/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp b/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
index a4ae501936..8eadc3d33f 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
@@ -12,6 +12,7 @@
 #include "Common/CommonTypes.h"
 #include "Common/MathUtil.h"
 #include "Common/x64Emitter.h"
+#include "Core/CoreTiming.h"
 #include "Core/PowerPC/Jit64/Jit.h"
 #include "Core/PowerPC/Jit64/RegCache/JitRegCache.h"
 #include "Core/PowerPC/Jit64Common/Jit64PowerPCState.h"
@@ -361,7 +362,15 @@ void Jit64::DoMergedBranch()
   // Code that handles successful PPC branching.
   const UGeckoInstruction& next = js.op[1].inst;
   const u32 nextPC = js.op[1].address;
-  if (next.OPCD == 16)  // bcx
+
+  if (js.op[1].branchIsIdleLoop)
+  {
+    if (next.LK)
+      MOV(32, PPCSTATE(spr[SPR_LR]), Imm32(nextPC + 4));
+
+    WriteIdleExit(js.op[1].branchTo);
+  }
+  else if (next.OPCD == 16)  // bcx
   {
     if (next.LK)
       MOV(32, PPCSTATE(spr[SPR_LR]), Imm32(nextPC + 4));
diff --git a/Source/Core/Core/PowerPC/Jit64/Jit_LoadStore.cpp b/Source/Core/Core/PowerPC/Jit64/Jit_LoadStore.cpp
index 3bab9436dd..a1cfe3976b 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit_LoadStore.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit_LoadStore.cpp
@@ -119,41 +119,6 @@ void Jit64::lXXx(UGeckoInstruction inst)
     signExtend = true;
   }
 
-  if (!CPU::IsStepping() && inst.OPCD == 32 && CanMergeNextInstructions(2) &&
-      (inst.hex & 0xFFFF0000) == 0x800D0000 &&
-      (js.op[1].inst.hex == 0x28000000 ||
-       (SConfig::GetInstance().bWii && js.op[1].inst.hex == 0x2C000000)) &&
-      js.op[2].inst.hex == 0x4182fff8)
-  {
-    s32 offset = (s32)(s16)inst.SIMM_16;
-    RCX64Reg Ra = gpr.Bind(a, RCMode::Read);
-    RCX64Reg Rd = gpr.Bind(d, RCMode::Write);
-    RegCache::Realize(Ra, Rd);
-
-    SafeLoadToReg(Rd, Ra, accessSize, offset, CallerSavedRegistersInUse(), signExtend);
-
-    // if it's still 0, we can wait until the next event
-    TEST(32, Rd, Rd);
-    FixupBranch noIdle = J_CC(CC_NZ);
-
-    BitSet32 registersInUse = CallerSavedRegistersInUse();
-    ABI_PushRegistersAndAdjustStack(registersInUse, 0);
-
-    ABI_CallFunction(CoreTiming::Idle);
-
-    ABI_PopRegistersAndAdjustStack(registersInUse, 0);
-
-    // ! we must continue executing of the loop after exception handling, maybe there is still 0 in
-    // r0
-    // MOV(32, PPCSTATE(pc), Imm32(js.compilerPC));
-    WriteExceptionExit();
-
-    SetJumpTarget(noIdle);
-
-    // js.compilerPC += 8;
-    return;
-  }
-
   // Determine whether this instruction updates inst.RA
   bool update;
   if (inst.OPCD == 31)
diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Branch.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Branch.cpp
index 9ac99abf67..97a81df2d4 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Branch.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Branch.cpp
@@ -76,12 +76,6 @@ void JitArm64::bx(UGeckoInstruction inst)
   INSTRUCTION_START
   JITDISABLE(bJITBranchOff);
 
-  u32 destination;
-  if (inst.AA)
-    destination = SignExt26(inst.LI << 2);
-  else
-    destination = js.compilerPC + SignExt26(inst.LI << 2);
-
   if (inst.LK)
   {
     ARM64Reg WA = gpr.GetReg();
@@ -105,7 +99,7 @@ void JitArm64::bx(UGeckoInstruction inst)
   gpr.Flush(FlushMode::FLUSH_ALL);
   fpr.Flush(FlushMode::FLUSH_ALL);
 
-  if (destination == js.compilerPC)
+  if (js.op->branchIsIdleLoop)
   {
     // make idle loops go faster
     ARM64Reg WA = gpr.GetReg();
@@ -115,11 +109,11 @@ void JitArm64::bx(UGeckoInstruction inst)
     BLR(XA);
     gpr.Unlock(WA);
 
-    WriteExceptionExit(js.compilerPC);
+    WriteExceptionExit(js.op->branchTo);
     return;
   }
 
-  WriteExit(destination, inst.LK, js.compilerPC + 4);
+  WriteExit(js.op->branchTo, inst.LK, js.compilerPC + 4);
 }
 
 void JitArm64::bcx(UGeckoInstruction inst)
@@ -160,16 +154,25 @@ void JitArm64::bcx(UGeckoInstruction inst)
   }
   gpr.Unlock(WA);
 
-  u32 destination;
-  if (inst.AA)
-    destination = SignExt16(inst.BD << 2);
-  else
-    destination = js.compilerPC + SignExt16(inst.BD << 2);
-
   gpr.Flush(FlushMode::FLUSH_MAINTAIN_STATE);
   fpr.Flush(FlushMode::FLUSH_MAINTAIN_STATE);
 
-  WriteExit(destination, inst.LK, js.compilerPC + 4);
+  if (js.op->branchIsIdleLoop)
+  {
+    // make idle loops go faster
+    ARM64Reg WA = gpr.GetReg();
+    ARM64Reg XA = EncodeRegTo64(WA);
+
+    MOVP2R(XA, &CoreTiming::Idle);
+    BLR(XA);
+    gpr.Unlock(WA);
+
+    WriteExceptionExit(js.op->branchTo);
+  }
+  else
+  {
+    WriteExit(js.op->branchTo, inst.LK, js.compilerPC + 4);
+  }
 
   SwitchToNearCode();
 
@@ -275,7 +278,20 @@ void JitArm64::bclrx(UGeckoInstruction inst)
   gpr.Flush(conditional ? FlushMode::FLUSH_MAINTAIN_STATE : FlushMode::FLUSH_ALL);
   fpr.Flush(conditional ? FlushMode::FLUSH_MAINTAIN_STATE : FlushMode::FLUSH_ALL);
 
-  WriteBLRExit(WA);
+  if (js.op->branchIsIdleLoop)
+  {
+    // make idle loops go faster
+    ARM64Reg XA = EncodeRegTo64(WA);
+
+    MOVP2R(XA, &CoreTiming::Idle);
+    BLR(XA);
+
+    WriteExceptionExit(js.op->branchTo);
+  }
+  else
+  {
+    WriteBLRExit(WA);
+  }
 
   gpr.Unlock(WA);
 
diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_LoadStore.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_LoadStore.cpp
index f0e5397f1c..7daad1ef91 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_LoadStore.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_LoadStore.cpp
@@ -346,37 +346,6 @@ void JitArm64::lXX(UGeckoInstruction inst)
   }
 
   SafeLoadToReg(d, update ? a : (a ? a : -1), offsetReg, flags, offset, update);
-
-  // LWZ idle skipping
-  if (inst.OPCD == 32 && CanMergeNextInstructions(2) &&
-      (inst.hex & 0xFFFF0000) == 0x800D0000 &&  // lwz r0, XXXX(r13)
-      (js.op[1].inst.hex == 0x28000000 ||
-       (SConfig::GetInstance().bWii && js.op[1].inst.hex == 0x2C000000)) &&  // cmpXwi r0,0
-      js.op[2].inst.hex == 0x4182fff8)                                       // beq -8
-  {
-    ARM64Reg WA = gpr.GetReg();
-    ARM64Reg XA = EncodeRegTo64(WA);
-
-    // if it's still 0, we can wait until the next event
-    FixupBranch noIdle = CBNZ(gpr.R(d));
-
-    FixupBranch far = B();
-    SwitchToFarCode();
-    SetJumpTarget(far);
-
-    gpr.Flush(FLUSH_MAINTAIN_STATE);
-    fpr.Flush(FLUSH_MAINTAIN_STATE);
-
-    MOVP2R(XA, &CoreTiming::Idle);
-    BLR(XA);
-    gpr.Unlock(WA);
-
-    WriteExceptionExit(js.compilerPC);
-
-    SwitchToNearCode();
-
-    SetJumpTarget(noIdle);
-  }
 }
 
 void JitArm64::stX(UGeckoInstruction inst)
diff --git a/Source/Core/Core/PowerPC/PPCAnalyst.cpp b/Source/Core/Core/PowerPC/PPCAnalyst.cpp
index 89c57b9bcb..7b18aa378f 100644
--- a/Source/Core/Core/PowerPC/PPCAnalyst.cpp
+++ b/Source/Core/Core/PowerPC/PPCAnalyst.cpp
@@ -640,6 +640,90 @@ void PPCAnalyzer::SetInstructionStats(CodeBlock* block, CodeOp* code, const Gekk
     code->outputCR0 = true;
     code->outputCR1 = true;
   }
+
+  code->branchUsesCtr = false;
+  code->branchTo = UINT32_MAX;
+
+  // For branch with immediate addresses (bx/bcx), compute the destination.
+  if (code->inst.OPCD == 18)  // bx
+  {
+    if (code->inst.AA)  // absolute
+      code->branchTo = SignExt26(code->inst.LI << 2);
+    else
+      code->branchTo = code->address + SignExt26(code->inst.LI << 2);
+  }
+  else if (code->inst.OPCD == 16)  // bcx
+  {
+    if (code->inst.AA)  // absolute
+      code->branchTo = SignExt16(code->inst.BD << 2);
+    else
+      code->branchTo = code->address + SignExt16(code->inst.BD << 2);
+    if (!(code->inst.BO & BO_DONT_DECREMENT_FLAG))
+      code->branchUsesCtr = true;
+  }
+  else if (code->inst.OPCD == 19 && code->inst.SUBOP10 == 16)  // bclrx
+  {
+    if (!(code->inst.BO & BO_DONT_DECREMENT_FLAG))
+      code->branchUsesCtr = true;
+  }
+  else if (code->inst.OPCD == 19 && code->inst.SUBOP10 == 528)  // bcctrx
+  {
+    if (!(code->inst.BO & BO_DONT_DECREMENT_FLAG))
+      code->branchUsesCtr = true;
+  }
+}
+
+bool PPCAnalyzer::IsBusyWaitLoop(CodeBlock* block, CodeOp* code, size_t instructions)
+{
+  // Very basic algorithm to detect busy wait loops:
+  //   * It loops to itself and does not contain any other branches.
+  //   * It does not write to memory.
+  //   * It only reads from registers it wrote to earlier in the loop, or it
+  //     does not write to these registers.
+  //
+  // Would benefit a lot from basic inlining support - a lot of the most
+  // used busy loops are DSP register interactions, which are bl/cmp/bne
+  // (with the bl target a pure function that follows the above rules). We
+  // don't detect these at the moment.
+  std::bitset<32> write_disallowed_regs;
+  std::bitset<32> written_regs;
+  for (size_t i = 0; i <= instructions; ++i)
+  {
+    if (code[i].opinfo->type == OpType::Branch)
+    {
+      if (code[i].branchUsesCtr)
+        return false;
+      if (code[i].branchTo == block->m_address && i == instructions)
+        return true;
+    }
+    else if (code[i].opinfo->type != OpType::Integer && code[i].opinfo->type != OpType::Load)
+    {
+      // In the future, some subsets of other instruction types might get
+      // supported. Right now, only try loops that have this very
+      // restricted instruction set.
+      return false;
+    }
+    else
+    {
+      for (int reg : code[i].regsIn)
+      {
+        if (reg == -1)
+          continue;
+        if (written_regs[reg])
+          continue;
+        write_disallowed_regs[reg] = true;
+      }
+      for (int reg : code[i].regsOut)
+      {
+        if (reg == -1)
+          continue;
+        if (write_disallowed_regs[reg])
+          return false;
+        written_regs[reg] = true;
+      }
+    }
+  }
+  return false;
 }
 
 u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std::size_t block_size)
@@ -692,8 +776,6 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std:
     code[i].opinfo = opinfo;
     code[i].address = address;
     code[i].inst = inst;
-    code[i].branchTo = UINT32_MAX;
-    code[i].branchToIndex = UINT32_MAX;
     code[i].skip = false;
     block->m_stats->numCycles += opinfo->numCycles;
     block->m_physical_addresses.insert(result.physical_address);
@@ -701,7 +783,6 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std:
     SetInstructionStats(block, &code[i], opinfo, static_cast<u32>(i));
 
     bool follow = false;
-    u32 destination = 0;
 
     bool conditional_continue = false;
 
@@ -709,13 +790,12 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std:
     //       If it is small, the performance will be down.
     //       If it is big, the size of generated code will be big and
     //       cache clearning will happen many times.
-    if (enable_follow && HasOption(OPTION_BRANCH_FOLLOW) && numFollows < BRANCH_FOLLOWING_THRESHOLD)
+    if (enable_follow && HasOption(OPTION_BRANCH_FOLLOW))
     {
       if (inst.OPCD == 18 && block_size > 1)
       {
         // Always follow BX instructions.
         follow = true;
-        destination = SignExt26(inst.LI << 2) + (inst.AA ? 0 : address);
         if (inst.LK)
         {
           found_call = true;
@@ -727,29 +807,31 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std:
       {
         // Always follow unconditional BCX instructions, but they are very rare.
         follow = true;
-        destination = SignExt16(inst.BD << 2) + (inst.AA ? 0 : address);
         if (inst.LK)
         {
           found_call = true;
           caller = i;
         }
       }
-      else if (inst.OPCD == 19 && inst.SUBOP10 == 16 && !inst.LK && found_call &&
-               (inst.BO & BO_DONT_DECREMENT_FLAG) && (inst.BO & BO_DONT_CHECK_CONDITION))
+      else if (inst.OPCD == 19 && inst.SUBOP10 == 16 && !inst.LK && found_call)
       {
-        // bclrx with unconditional branch = return
-        // Follow it if we can propagate the LR value of the last CALL instruction.
-        // Through it would be easy to track the upper level of call/return,
-        // we can't guarantee the LR value. The PPC ABI forces all functions to push
-        // the LR value on the stack as there are no spare registers. So we'd need
-        // to check all store instruction to not alias with the stack.
-        follow = true;
-        destination = code[caller].address + 4;
-        found_call = false;
-        code[i].skip = true;
+        code[i].branchTo = code[caller].address + 4;
+        if ((inst.BO & BO_DONT_DECREMENT_FLAG) && (inst.BO & BO_DONT_CHECK_CONDITION) &&
+            numFollows < BRANCH_FOLLOWING_THRESHOLD)
+        {
+          // bclrx with unconditional branch = return
+          // Follow it if we can propagate the LR value of the last CALL instruction.
+          // Through it would be easy to track the upper level of call/return,
+          // we can't guarantee the LR value. The PPC ABI forces all functions to push
+          // the LR value on the stack as there are no spare registers. So we'd need
+          // to check all store instruction to not alias with the stack.
+          follow = true;
+          found_call = false;
+          code[i].skip = true;
 
-        // Skip the RET, so also don't generate the stack entry for the BLR optimization.
-        code[caller].skipLRStack = true;
+          // Skip the RET, so also don't generate the stack entry for the BLR optimization.
+          code[caller].skipLRStack = true;
+        }
       }
       else if (inst.OPCD == 31 && inst.SUBOP10 == 467)
       {
@@ -792,11 +874,14 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock* block, CodeBuffer* buffer, std:
       }
     }
 
-    if (follow)
+    code[i].branchIsIdleLoop =
+        code[i].branchTo == block->m_address && IsBusyWaitLoop(block, code, i);
+
+    if (follow && numFollows < BRANCH_FOLLOWING_THRESHOLD)
     {
       // Follow the unconditional branch.
       numFollows++;
-      address = destination;
+      address = code[i].branchTo;
     }
     else
     {
diff --git a/Source/Core/Core/PowerPC/PPCAnalyst.h b/Source/Core/Core/PowerPC/PPCAnalyst.h
index 18fa3a4fb2..b74d1d0167 100644
--- a/Source/Core/Core/PowerPC/PPCAnalyst.h
+++ b/Source/Core/Core/PowerPC/PPCAnalyst.h
@@ -27,13 +27,14 @@ struct CodeOp  // 16B
   UGeckoInstruction inst;
   GekkoOPInfo* opinfo;
   u32 address;
-  u32 branchTo;       // if 0, not a branch
-  int branchToIndex;  // index of target block
+  u32 branchTo;  // if UINT32_MAX, not a branch
   BitSet32 regsOut;
   BitSet32 regsIn;
   BitSet32 fregsIn;
   s8 fregOut;
   bool isBranchTarget;
+  bool branchUsesCtr;
+  bool branchIsIdleLoop;
   bool wantsCR0;
   bool wantsCR1;
   bool wantsFPRF;
@@ -213,6 +214,7 @@ private:
   void ReorderInstructionsCore(u32 instructions, CodeOp* code, bool reverse, ReorderType type);
   void ReorderInstructions(u32 instructions, CodeOp* code);
   void SetInstructionStats(CodeBlock* block, CodeOp* code, const GekkoOPInfo* opinfo, u32 index);
+  bool IsBusyWaitLoop(CodeBlock* block, CodeOp* code, size_t instructions);
 
   // Options
   u32 m_options = 0;