[InstCombine] Use combineMetadataForCSE in phi of loads fold

Use combineMetadataForCSE instead of manually enumerating known
metadata kinds. This is a typical sinking transform for which
combineMetadataForCSE is safe to use (with DoesKMove=true).

Part of #121495.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp

@@ -765,33 +765,14 @@ Instruction *InstCombinerImpl::foldPHIArgLoadIntoPHI(PHINode &PN) {
   NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
   LoadInst *NewLI =
       new LoadInst(FirstLI->getType(), NewPN, "", IsVolatile, LoadAlignment);
-
-  unsigned KnownIDs[] = {
-    LLVMContext::MD_tbaa,
-    LLVMContext::MD_range,
-    LLVMContext::MD_invariant_load,
-    LLVMContext::MD_alias_scope,
-    LLVMContext::MD_noalias,
-    LLVMContext::MD_nonnull,
-    LLVMContext::MD_align,
-    LLVMContext::MD_dereferenceable,
-    LLVMContext::MD_dereferenceable_or_null,
-    LLVMContext::MD_access_group,
-    LLVMContext::MD_noundef,
-  };
-
-  for (unsigned ID : KnownIDs)
-    NewLI->setMetadata(ID, FirstLI->getMetadata(ID));
+  NewLI->copyMetadata(*FirstLI);
 
   // Add all operands to the new PHI and combine TBAA metadata.
   for (auto Incoming : drop_begin(zip(PN.blocks(), PN.incoming_values()))) {
     BasicBlock *BB = std::get<0>(Incoming);
     Value *V = std::get<1>(Incoming);
     LoadInst *LI = cast<LoadInst>(V);
-    // FIXME: https://github.com/llvm/llvm-project/issues/121495
-    // Call combineMetadataForCSE instead, so that an explicit set of KnownIDs
-    // doesn't need to be maintained here.
-    combineMetadata(NewLI, LI, KnownIDs, true);
+    combineMetadataForCSE(NewLI, LI, true);
     Value *NewInVal = LI->getOperand(0);
     if (NewInVal != InVal)
       InVal = nullptr;