diff --git a/include/xenia/cpu/codegen/function_generator.h b/include/xenia/cpu/codegen/function_generator.h
index 635f713e4..08eaeabdf 100644
--- a/include/xenia/cpu/codegen/function_generator.h
+++ b/include/xenia/cpu/codegen/function_generator.h
@@ -93,12 +93,7 @@ private:
   void GenerateSharedBlocks();
   void PrepareBasicBlock(sdb::FunctionBlock* block);
   void GenerateBasicBlock(sdb::FunctionBlock* block);
-
-  void setup_xer();
-  void setup_lr();
-  void setup_ctr();
-  void setup_cr(uint32_t n);
-  void setup_gpr(uint32_t n);
+  void SetupLocals();
 
   xe_memory_ref         memory_;
   sdb::SymbolDatabase*  sdb_;
diff --git a/src/cpu/codegen/emit_alu.cc b/src/cpu/codegen/emit_alu.cc
index e8acedc79..deb43e4d6 100644
--- a/src/cpu/codegen/emit_alu.cc
+++ b/src/cpu/codegen/emit_alu.cc
@@ -311,7 +311,9 @@ XEEMITTER(divwux,       0x7C000396, XO )(FunctionGenerator& g, IRBuilder<>& b, I
   g.update_gpr_value(i.XO.RT, v);
 
   // If we are OE=1 we need to clear the overflow bit.
-  g.update_xer_with_overflow(b.getInt1(0));
+  if (i.XO.OE) {
+    g.update_xer_with_overflow(b.getInt1(0));
+  }
 
   if (i.XO.Rc) {
     // With cr0 update.
@@ -1018,10 +1020,10 @@ XEDISASMR(ori,          0x60000000, D  )(InstrData& i, InstrDisasm& d) {
     d.Init("no-op", "OR Immediate", 0);
   } else {
     d.Init("ori", "OR Immediate", 0);
-    d.AddRegOperand(InstrRegister::kGPR, i.D.RA, InstrRegister::kWrite);
-    d.AddRegOperand(InstrRegister::kGPR, i.D.RT, InstrRegister::kRead);
-    d.AddUImmOperand(i.D.DS, 2);
   }
+  d.AddRegOperand(InstrRegister::kGPR, i.D.RA, InstrRegister::kWrite);
+  d.AddRegOperand(InstrRegister::kGPR, i.D.RT, InstrRegister::kRead);
+  d.AddUImmOperand(i.D.DS, 2);
   return d.Finish();
 }
 XEEMITTER(ori,          0x60000000, D  )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
diff --git a/src/cpu/codegen/emit_control.cc b/src/cpu/codegen/emit_control.cc
index 339045b4d..e8ba9e847 100644
--- a/src/cpu/codegen/emit_control.cc
+++ b/src/cpu/codegen/emit_control.cc
@@ -275,6 +275,7 @@ XEDISASMR(bcctrx,       0x4C000420, XL )(InstrData& i, InstrDisasm& d) {
   }
   d.AddUImmOperand(i.XL.BO, 1);
   d.AddUImmOperand(i.XL.BI, 1);
+  d.AddCTR(InstrRegister::kRead);
   return d.Finish();
 }
 XEEMITTER(bcctrx,       0x4C000420, XL )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
@@ -352,6 +353,7 @@ XEDISASMR(bclrx,        0x4C000020, XL )(InstrData& i, InstrDisasm& d) {
   }
   d.AddUImmOperand(i.XL.BO, 1);
   d.AddUImmOperand(i.XL.BI, 1);
+  d.AddLR(InstrRegister::kRead);
   return d.Finish();
 }
 XEEMITTER(bclrx,        0x4C000020, XL )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
@@ -591,6 +593,12 @@ int XeEmitTrap(FunctionGenerator& g, IRBuilder<>& b, InstrData& i,
   return 0;
 }
 
+XEDISASMR(td,           0x7C000088, X  )(InstrData& i, InstrDisasm& d) {
+  d.Init("td", "Trap Doubleword", 0);
+  d.AddRegOperand(InstrRegister::kGPR, i.X.RA, InstrRegister::kRead);
+  d.AddRegOperand(InstrRegister::kGPR, i.X.RB, InstrRegister::kRead);
+  return d.Finish();
+}
 XEEMITTER(td,           0x7C000088, X  )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
   // a <- (RA)
   // b <- (RB)
@@ -605,6 +613,11 @@ XEEMITTER(td,           0x7C000088, X  )(FunctionGenerator& g, IRBuilder<>& b, I
                     i.X.RT);
 }
 
+XEDISASMR(tdi,          0x08000000, D  )(InstrData& i, InstrDisasm& d) {
+  d.Init("tdi", "Trap Doubleword Immediate", 0);
+  d.AddRegOperand(InstrRegister::kGPR, i.D.RA, InstrRegister::kRead);
+  return d.Finish();
+}
 XEEMITTER(tdi,          0x08000000, D  )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
   // a <- (RA)
   // if (a < EXTS(SI)) & TO[0] then TRAP
@@ -618,6 +631,12 @@ XEEMITTER(tdi,          0x08000000, D  )(FunctionGenerator& g, IRBuilder<>& b, I
                     i.D.RT);
 }
 
+XEDISASMR(tw,           0x7C000008, X  )(InstrData& i, InstrDisasm& d) {
+  d.Init("tw", "Trap Word", 0);
+  d.AddRegOperand(InstrRegister::kGPR, i.X.RA, InstrRegister::kRead);
+  d.AddRegOperand(InstrRegister::kGPR, i.X.RB, InstrRegister::kRead);
+  return d.Finish();
+}
 XEEMITTER(tw,           0x7C000008, X  )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
   // a <- EXTS((RA)[32:63])
   // b <- EXTS((RB)[32:63])
@@ -636,6 +655,11 @@ XEEMITTER(tw,           0x7C000008, X  )(FunctionGenerator& g, IRBuilder<>& b, I
                     i.X.RT);
 }
 
+XEDISASMR(twi,          0x0C000000, D  )(InstrData& i, InstrDisasm& d) {
+  d.Init("twi", "Trap Word Immediate", 0);
+  d.AddRegOperand(InstrRegister::kGPR, i.D.RA, InstrRegister::kRead);
+  return d.Finish();
+}
 XEEMITTER(twi,          0x0C000000, D  )(FunctionGenerator& g, IRBuilder<>& b, InstrData& i) {
   // a <- EXTS((RA)[32:63])
   // if (a < EXTS(SI)) & TO[0] then TRAP
@@ -782,10 +806,10 @@ void RegisterEmitCategoryControl() {
   XEREGISTEREMITTER(crxor,        0x4C000182);
   XEREGISTEREMITTER(mcrf,         0x4C000000);
   XEREGISTEREMITTER(sc,           0x44000002);
-  XEREGISTEREMITTER(td,           0x7C000088);
-  XEREGISTEREMITTER(tdi,          0x08000000);
-  XEREGISTEREMITTER(tw,           0x7C000008);
-  XEREGISTEREMITTER(twi,          0x0C000000);
+  XEREGISTERINSTR(td,           0x7C000088);
+  XEREGISTERINSTR(tdi,          0x08000000);
+  XEREGISTERINSTR(tw,           0x7C000008);
+  XEREGISTERINSTR(twi,          0x0C000000);
   XEREGISTEREMITTER(mfcr,         0x7C000026);
   XEREGISTERINSTR(mfspr,        0x7C0002A6);
   XEREGISTEREMITTER(mftb,         0x7C0002E6);
diff --git a/src/cpu/codegen/function_generator.cc b/src/cpu/codegen/function_generator.cc
index 852e6f829..b550a94d7 100644
--- a/src/cpu/codegen/function_generator.cc
+++ b/src/cpu/codegen/function_generator.cc
@@ -155,6 +155,9 @@ void FunctionGenerator::GenerateBasicBlocks() {
     PrepareBasicBlock(block);
   }
 
+  // Setup all local variables now that we know what we need.
+  SetupLocals();
+
   // Pass 2 fills in instructions.
   for (std::map<uint32_t, FunctionBlock*>::iterator it = fn_->blocks.begin();
        it != fn_->blocks.end(); ++it) {
@@ -240,8 +243,11 @@ void FunctionGenerator::PrepareBasicBlock(FunctionBlock* block) {
       continue;
     }
 
+    // We really need to know the registers modified, so die if we've been lazy
+    // and haven't implemented the disassemble method yet.
     ppc::InstrDisasm d;
-    i.type->disassemble(i, d);
+    XEASSERTNOTNULL(i.type->disassemble);
+    XEASSERTZERO(i.type->disassemble(i, d));
 
     // Accumulate access bits.
     access_bits.Extend(d.access_bits);
@@ -488,8 +494,43 @@ void FunctionGenerator::StoreStateValue(uint32_t offset, Type* type,
   b.CreateStore(value, ptr);
 }
 
-Value* FunctionGenerator::cia_value() {
-  return builder_->getInt32(cia_);
+void FunctionGenerator::SetupLocals() {
+  IRBuilder<>& b = *builder_;
+
+  uint64_t spr_t = access_bits_.spr;
+  if (spr_t & 0x3) {
+    locals_.xer = SetupLocal(b.getInt64Ty(), "xer");
+  }
+  spr_t >>= 2;
+  if (spr_t & 0x3) {
+    locals_.lr = SetupLocal(b.getInt64Ty(), "lr");
+  }
+  spr_t >>= 2;
+  if (spr_t & 0x3) {
+    locals_.ctr = SetupLocal(b.getInt64Ty(), "ctr");
+  }
+  spr_t >>= 2;
+  // TODO: FPCSR
+
+  char name[32];
+
+  uint64_t cr_t = access_bits_.cr;
+  for (int n = 0; n < 8; n++) {
+    if (cr_t & 3) {
+      xesnprintfa(name, XECOUNT(name), "cr%d", n);
+      locals_.cr[n] = SetupLocal(b.getInt8Ty(), name);
+    }
+    cr_t >>= 2;
+  }
+
+  uint64_t gpr_t = access_bits_.gpr;
+  for (int n = 0; n < 32; n++) {
+    if (gpr_t & 3) {
+      xesnprintfa(name, XECOUNT(name), "r%d", n);
+      locals_.gpr[n] = SetupLocal(b.getInt64Ty(), name);
+    }
+    gpr_t >>= 2;
+  }
 }
 
 Value* FunctionGenerator::SetupLocal(llvm::Type* type, const char* name) {
@@ -502,11 +543,18 @@ Value* FunctionGenerator::SetupLocal(llvm::Type* type, const char* name) {
   return v;
 }
 
+Value* FunctionGenerator::cia_value() {
+  return builder_->getInt32(cia_);
+}
+
 void FunctionGenerator::FillRegisters() {
   // This updates all of the local register values from the state memory.
   // It should be called on function entry for initial setup and after any
   // calls that may modify the registers.
 
+  // TODO(benvanik): use access flags to see if we need to do reads/writes.
+  // Though LLVM may do a better job than we can, except across calls.
+
   IRBuilder<>& b = *builder_;
 
   if (locals_.xer) {
@@ -619,29 +667,16 @@ void FunctionGenerator::SpillRegisters() {
   }
 }
 
-void FunctionGenerator::setup_xer() {
-  IRBuilder<>& b = *builder_;
-
-  if (locals_.xer) {
-    return;
-  }
-
-  locals_.xer = SetupLocal(b.getInt64Ty(), "xer");
-}
-
 Value* FunctionGenerator::xer_value() {
+  XEASSERTNOTNULL(locals_.xer);
   IRBuilder<>& b = *builder_;
-
-  setup_xer();
-
   return b.CreateLoad(locals_.xer);
 }
 
 void FunctionGenerator::update_xer_value(Value* value) {
+  XEASSERTNOTNULL(locals_.xer);
   IRBuilder<>& b = *builder_;
 
-  setup_xer();
-
   // Extend to 64bits if needed.
   if (!value->getType()->isIntegerTy(64)) {
     value = b.CreateZExt(value, b.getInt64Ty());
@@ -650,10 +685,9 @@ void FunctionGenerator::update_xer_value(Value* value) {
 }
 
 void FunctionGenerator::update_xer_with_overflow(Value* value) {
+  XEASSERTNOTNULL(locals_.xer);
   IRBuilder<>& b = *builder_;
 
-  setup_xer();
-
   // Expects a i1 indicating overflow.
   // Trust the caller that if it's larger than that it's already truncated.
   if (!value->getType()->isIntegerTy(64)) {
@@ -668,10 +702,9 @@ void FunctionGenerator::update_xer_with_overflow(Value* value) {
 }
 
 void FunctionGenerator::update_xer_with_carry(Value* value) {
+  XEASSERTNOTNULL(locals_.xer);
   IRBuilder<>& b = *builder_;
 
-  setup_xer();
-
   // Expects a i1 indicating carry.
   // Trust the caller that if it's larger than that it's already truncated.
   if (!value->getType()->isIntegerTy(64)) {
@@ -685,10 +718,9 @@ void FunctionGenerator::update_xer_with_carry(Value* value) {
 }
 
 void FunctionGenerator::update_xer_with_overflow_and_carry(Value* value) {
+  XEASSERTNOTNULL(locals_.xer);
   IRBuilder<>& b = *builder_;
 
-  setup_xer();
-
   // Expects a i1 indicating overflow.
   // Trust the caller that if it's larger than that it's already truncated.
   if (!value->getType()->isIntegerTy(64)) {
@@ -705,29 +737,16 @@ void FunctionGenerator::update_xer_with_overflow_and_carry(Value* value) {
   b.CreateStore(xer, locals_.xer);
 }
 
-void FunctionGenerator::setup_lr() {
-  IRBuilder<>& b = *builder_;
-
-  if (locals_.lr) {
-    return;
-  }
-
-  locals_.lr = SetupLocal(b.getInt64Ty(), "lr");
-}
-
 Value* FunctionGenerator::lr_value() {
+  XEASSERTNOTNULL(locals_.lr);
   IRBuilder<>& b = *builder_;
-
-  setup_lr();
-
   return b.CreateLoad(locals_.lr);
 }
 
 void FunctionGenerator::update_lr_value(Value* value) {
+  XEASSERTNOTNULL(locals_.lr);
   IRBuilder<>& b = *builder_;
 
-  setup_lr();
-
   // Extend to 64bits if needed.
   if (!value->getType()->isIntegerTy(64)) {
     value = b.CreateZExt(value, b.getInt64Ty());
@@ -735,29 +754,17 @@ void FunctionGenerator::update_lr_value(Value* value) {
   b.CreateStore(value, locals_.lr);
 }
 
-void FunctionGenerator::setup_ctr() {
-  IRBuilder<>& b = *builder_;
-
-  if (locals_.ctr) {
-    return;
-  }
-
-  locals_.ctr = SetupLocal(b.getInt64Ty(), "ctr");
-}
-
 Value* FunctionGenerator::ctr_value() {
+  XEASSERTNOTNULL(locals_.ctr);
   IRBuilder<>& b = *builder_;
 
-  setup_ctr();
-
   return b.CreateLoad(locals_.ctr);
 }
 
 void FunctionGenerator::update_ctr_value(Value* value) {
+  XEASSERTNOTNULL(locals_.ctr);
   IRBuilder<>& b = *builder_;
 
-  setup_ctr();
-
   // Extend to 64bits if needed.
   if (!value->getType()->isIntegerTy(64)) {
     value = b.CreateZExt(value, b.getInt64Ty());
@@ -765,34 +772,21 @@ void FunctionGenerator::update_ctr_value(Value* value) {
   b.CreateStore(value, locals_.ctr);
 }
 
-void FunctionGenerator::setup_cr(uint32_t n) {
-  IRBuilder<>& b = *builder_;
-
-  XEASSERT(n >= 0 && n < 8);
-  if (locals_.cr[n]) {
-    return;
-  }
-
-  char name[32];
-  xesnprintfa(name, XECOUNT(name), "cr_f%d", n);
-  locals_.cr[n] = SetupLocal(b.getInt8Ty(), name);
-}
-
 Value* FunctionGenerator::cr_value(uint32_t n) {
+  XEASSERT(n >= 0 && n < 8);
+  XEASSERTNOTNULL(locals_.cr[n]);
   IRBuilder<>& b = *builder_;
 
-  setup_cr(n);
-
   Value* v = b.CreateLoad(locals_.cr[n]);
   v = b.CreateZExt(v, b.getInt64Ty());
   return v;
 }
 
 void FunctionGenerator::update_cr_value(uint32_t n, Value* value) {
+  XEASSERT(n >= 0 && n < 8);
+  XEASSERTNOTNULL(locals_.cr[n]);
   IRBuilder<>& b = *builder_;
 
-  setup_cr(n);
-
   // Truncate to 8 bits if needed.
   // TODO(benvanik): also widen?
   if (!value->getType()->isIntegerTy(8)) {
@@ -834,22 +828,10 @@ void FunctionGenerator::update_cr_with_cond(
   update_cr_value(n, c);
 }
 
-void FunctionGenerator::setup_gpr(uint32_t n) {
-  IRBuilder<>& b = *builder_;
-
-  if (locals_.gpr[n]) {
-    return;
-  }
-
-  char name[30];
-  xesnprintfa(name, XECOUNT(name), "gpr_r%d", n);
-  locals_.gpr[n] = SetupLocal(b.getInt64Ty(), name);
-}
-
 Value* FunctionGenerator::gpr_value(uint32_t n) {
-  IRBuilder<>& b = *builder_;
-
   XEASSERT(n >= 0 && n < 32);
+  XEASSERTNOTNULL(locals_.gpr[n]);
+  IRBuilder<>& b = *builder_;
 
   // Actually r0 is writable, even though nobody should ever do that.
   // Perhaps we can check usage and enable this if safe?
@@ -858,15 +840,13 @@ Value* FunctionGenerator::gpr_value(uint32_t n) {
   //   return b.getInt64(0);
   // }
 
-  setup_gpr(n);
-
   return b.CreateLoad(locals_.gpr[n]);
 }
 
 void FunctionGenerator::update_gpr_value(uint32_t n, Value* value) {
-  IRBuilder<>& b = *builder_;
-
   XEASSERT(n >= 0 && n < 32);
+  XEASSERTNOTNULL(locals_.gpr[n]);
+  IRBuilder<>& b = *builder_;
 
   // See above - r0 can be written.
   // if (n == 0) {
@@ -874,8 +854,6 @@ void FunctionGenerator::update_gpr_value(uint32_t n, Value* value) {
   //   return;
   // }
 
-  setup_gpr(n);
-
   // Extend to 64bits if needed.
   if (!value->getType()->isIntegerTy(64)) {
     value = b.CreateZExt(value, b.getInt64Ty());