[ArgumentPromotion]: Copy function metadata after promoting arguments

[etiotto]

Summary

The argument promotion pass currently fails to copy function annotations over to the modified function after promoting arguments.
This patch copies the original function annotation to the new function.

[fhahn]

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

220–222

That should not be necessary anymore now that we copy all the metadata?

One thing we need to keep in mind is that the original function may not be deleted and there are some kinds of metadata that need to be unique per function (.e.g !dbg), hence the F->setSubprogram(nullptr) below. With the change, it might be good to add a comment why we need to remove the !dbg metadata from the original function. But I am not aware of any other metadata nodes that have a similar constraint.

[etiotto]

Fix quotes in profile.ll

[etiotto]

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

220–222

Good point. I'll drop this line and add the comment you suggested.

[etiotto]

Address code review comments.

[etiotto]

ping

[fhahn]

LGTM, thanks! For the commit message, I think saying 'copy function metadata' instead of 'function annotations' is more accurate. Also there seems to be a stray : in the title.

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote,
 
   // Construct the new function type using the new arguments.
   FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
 
   // Create the new function body and insert it into the module.
   Function *NF = Function::Create(NFTy, F->getLinkage(), F->getAddressSpace(),
                                   F->getName());
   NF->copyAttributesFrom(F);
+  NF->copyMetadata(F, 0);
 
-  // Patch the pointer to LLVM function in debug info descriptor.
-  NF->setSubprogram(F->getSubprogram());
+  // The new function will have the !dbg metadata copied from the original
+  // function. The original function may not be deleted, and dbg metadata need
+  // to be unique so we need to drop it.
   F->setSubprogram(nullptr);
 
   LLVM_DEBUG(dbgs() << "ARG PROMOTION:  Promoting to:" << *NF << "\n"
                     << "From: " << *F);
 
   // Recompute the parameter attributes list based on the new arguments for
   // the function.
   NF->setAttributes(AttributeList::get(F->getContext(), PAL.getFnAttributes(),

llvm/test/Transforms/ArgumentPromotion/profile.ll

 ; CHECK-NEXT:    ret void
 ;
   %x = alloca i32
   store i32 42, i32* %x
   call void @promote_i32_ptr(i32* %x), !prof !0
   ret void
 }
 
-define internal void @promote_i32_ptr(i32* %xp) {
+define internal void @promote_i32_ptr(i32* %xp) !prof !1 {
 ; CHECK-LABEL: define {{[^@]+}}@promote_i32_ptr
-; CHECK-SAME: (i32 [[XP_VAL:%.*]])
+; CHECK-SAME: (i32 [[XP_VAL:%.*]]) !prof !1
 ; CHECK-NEXT:    call void @use_i32(i32 [[XP_VAL]])
 ; CHECK-NEXT:    ret void
 ;
   %x = load i32, i32* %xp
   call void @use_i32(i32 %x)
   ret void
 }
 
 declare void @use_i32(i32)
 
 !0 = !{!"branch_weights", i32 30}
+!1 = !{!"function_entry_count", i64 100}