InstSimplify: Refactor function to use more switches

[arsenm]

Summary

Did you mean to remove the NumOperands splitting and have one giant switch?

[efriedma]

LGTM. The common LHS and RHS variables seem like a good enough reason to separate it into two switches.

[arsenm]

r291634

lib/Analysis/InstructionSimplify.cpp

static bool maskIsAllZeroOrUndef(Value *Mask) {
   return true;
 }
 
 template <typename IterTy>
 static Value *SimplifyIntrinsic(Function *F, IterTy ArgBegin, IterTy ArgEnd,
                                 const Query &Q, unsigned MaxRecurse) {
   Intrinsic::ID IID = F->getIntrinsicID();
   unsigned NumOperands = std::distance(ArgBegin, ArgEnd);
-  Type *ReturnType = F->getReturnType();
+
+  // Unary Ops
+  if (NumOperands == 1) {
+    // Perform idempotent optimizations
+    if (IsIdempotent(IID)) {
+      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin)) {
+        if (II->getIntrinsicID() == IID)
+          return II;
+      }
+    }
+
+    switch (IID) {
+    case Intrinsic::fabs: {
+      if (CannotBeNegative(*ArgBegin, Q.TLI))
+        return *ArgBegin;
+    }
+    default:
+      return nullptr;
+    }
+  }
 
   // Binary Ops
   if (NumOperands == 2) {
     Value *LHS = *ArgBegin;
     Value *RHS = *(ArgBegin + 1);
-    if (IID == Intrinsic::usub_with_overflow ||
-        IID == Intrinsic::ssub_with_overflow) {
+    Type *ReturnType = F->getReturnType();
+
+    switch (IID) {
+    case Intrinsic::usub_with_overflow:
+    case Intrinsic::ssub_with_overflow: {
       // X - X -> { 0, false }
       if (LHS == RHS)
         return Constant::getNullValue(ReturnType);
 
       // X - undef -> undef
       // undef - X -> undef
       if (isa<UndefValue>(LHS) || isa<UndefValue>(RHS))
         return UndefValue::get(ReturnType);
-    }
 
-    if (IID == Intrinsic::uadd_with_overflow ||
-        IID == Intrinsic::sadd_with_overflow) {
+      return nullptr;
+    }
+    case Intrinsic::uadd_with_overflow:
+    case Intrinsic::sadd_with_overflow: {
       // X + undef -> undef
       if (isa<UndefValue>(RHS))
         return UndefValue::get(ReturnType);
-    }
 
-    if (IID == Intrinsic::umul_with_overflow ||
-        IID == Intrinsic::smul_with_overflow) {
+      return nullptr;
+    }
+    case Intrinsic::umul_with_overflow:
+    case Intrinsic::smul_with_overflow: {
       // X * 0 -> { 0, false }
       if (match(RHS, m_Zero()))
         return Constant::getNullValue(ReturnType);
 
       // X * undef -> { 0, false }
       if (match(RHS, m_Undef()))
         return Constant::getNullValue(ReturnType);
-    }
 
-    if (IID == Intrinsic::load_relative && isa<Constant>(LHS) &&
-        isa<Constant>(RHS))
-      return SimplifyRelativeLoad(cast<Constant>(LHS), cast<Constant>(RHS),
-                                  Q.DL);
+      return nullptr;
+    }
+    case Intrinsic::load_relative: {
+      Constant *C0 = dyn_cast<Constant>(LHS);
+      Constant *C1 = dyn_cast<Constant>(RHS);
+      if (C0 && C1)
+        return SimplifyRelativeLoad(C0, C1, Q.DL);
+      return nullptr;
+    }
+    default:
+      return nullptr;
+    }
   }
 
   // Simplify calls to llvm.masked.load.*
-  if (IID == Intrinsic::masked_load) {
+  switch (IID) {
+  case Intrinsic::masked_load: {
     Value *MaskArg = ArgBegin[2];
     Value *PassthruArg = ArgBegin[3];
     // If the mask is all zeros or undef, the "passthru" argument is the result.
     if (maskIsAllZeroOrUndef(MaskArg))
       return PassthruArg;
-  }
-
-  // Perform idempotent optimizations
-  if (!IsIdempotent(IID))
     return nullptr;
-
-  // Unary Ops
-  if (NumOperands == 1) {
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*ArgBegin)) {
-      if (II->getIntrinsicID() == IID)
-        return II;
-    }
-
-    switch (IID) {
-    case Intrinsic::fabs: {
-      if (CannotBeNegative(*ArgBegin, Q.TLI))
-        return *ArgBegin;
-    }
-    default:
-      break;
-    }
-  }
-
     return nullptr;
   }
+}
 
 template <typename IterTy>
 static Value *SimplifyCall(Value *V, IterTy ArgBegin, IterTy ArgEnd,
                            const Query &Q, unsigned MaxRecurse) {
   Type *Ty = V->getType();
   if (PointerType *PTy = dyn_cast<PointerType>(Ty))
     Ty = PTy->getElementType();
   FunctionType *FTy = cast<FunctionType>(Ty);