[llvm[NFC] Adjust mem fn auto upgrade detection

[urnathan]

Summary

In working on how to augment llvm.memcpy and friends to distingish src from dst volatility I noticed the auto upgrade processing was somewhat duplicative. This commonizes the memcpy and memmove detection. In addition to being general goodness, this will make it easier to do the change I want to make.

This change itself is NFC

[jroelofs]

LGTM

llvm/lib/IR/AutoUpgrade.cpp

1105–1116

llvm::StringSwitch might be a touch nicer for this

[urnathan]

let's try with StringSwitch ... will commit if tests pass

llvm/lib/IR/AutoUpgrade.cpp

1105–1116

Sounds good

[urnathan]

b6c220da0219 2023-07-28 | [llvm][NFC] Adjust mem fn auto upgrade detection

llvm/lib/IR/AutoUpgrade.cpp

if (Name.startswith("masked.scatter.")) {
         NewFn = Intrinsic::getDeclaration(F->getParent(),
                                           Intrinsic::masked_scatter, Tys);
         return true;
       }
     }
     // Updating the memory intrinsics (memcpy/memmove/memset) that have an
     // alignment parameter to embedding the alignment as an attribute of
     // the pointer args.
-    if (Name.startswith("memcpy.") && F->arg_size() == 5) {
+    if (unsigned ID = StringSwitch<unsigned>(Name)
+                          .StartsWith("memcpy.", Intrinsic::memcpy)
+                          .StartsWith("memmove.", Intrinsic::memmove)
+                          .Default(0)) {
+      if (F->arg_size() == 5) {
         rename(F);
         // Get the types of dest, src, and len
-      ArrayRef<Type *> ParamTypes = F->getFunctionType()->params().slice(0, 3);
-      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::memcpy,
-                                        ParamTypes);
+        ArrayRef<Type *> ParamTypes =
+            F->getFunctionType()->params().slice(0, 3);
+        NewFn = Intrinsic::getDeclaration(F->getParent(), ID, ParamTypes);
         return true;
       }
-    if (Name.startswith("memmove.") && F->arg_size() == 5) {
-      rename(F);
-      // Get the types of dest, src, and len
-      ArrayRef<Type *> ParamTypes = F->getFunctionType()->params().slice(0, 3);
-      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::memmove,
-                                        ParamTypes);
-      return true;
     }
     if (Name.startswith("memset.") && F->arg_size() == 5) {
       rename(F);
       // Get the types of dest, and len
       const auto *FT = F->getFunctionType();
       Type *ParamTypes[2] = {
           FT->getParamType(0), // Dest
           FT->getParamType(2)  // len