Refine ArgPromotion metadata handling

[tejohnson]

Summary

In r353537 we now copy all metadata to the new function, with the old
being removed when the old function is eliminated. In some cases the old
function is dropped to a declaration (seems to only occur with the old
PM). Go ahead and clear all metadata from the old function to handle that
case, since verification will complain otherwise. This is consistent
with what was being done for debug metadata before r353537.

[davidxl]

lib/Transforms/IPO/ArgumentPromotion.cpp

220

Is it possible to assert F becomes a decl?

[tejohnson]

Add assert

[davidxl]

lgtm

[uabelho]

Thanks for fixing!

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);
+  F->clearMetadata();
 
   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(),
                                        PAL.getRetAttributes(), ArgAttrVec));
while (!I->use_empty()) {
         GEP->eraseFromParent();
       }
     }
 
     // Increment I2 past all of the arguments added for this promoted pointer.
     std::advance(I2, ArgIndices.size());
   }
 
+  assert(F->isDeclaration());
   return NF;
 }
 
 /// AllCallersPassInValidPointerForArgument - Return true if we can prove that
 /// all callees pass in a valid pointer for the specified function argument.
 static bool allCallersPassInValidPointerForArgument(Argument *Arg) {
   Function *Callee = Arg->getParent();
   const DataLayout &DL = Callee->getParent()->getDataLayout();

test/Transforms/ArgumentPromotion/dbg2.ll

+; RUN: opt < %s -argpromotion -instcombine -S | FileCheck %s
+
+%f_ty = type void (i8*)*
+
+define void @foo() {
+entry:
+  %f_p = getelementptr inbounds %f_ty, %f_ty* null, i32 0
+  store %f_ty @bar, %f_ty* %f_p, align 1
+  ret void
+}
+
+define internal void @bar(i8*) !dbg !1 {
+entry:
+  ret void
+}
+
+; The new copy should get the !dbg metadata
+; CHECK: define internal void @bar() !dbg
+; The old copy should now be a declaration without any !dbg metadata
+; CHECK-NOT: declare dso_local void @0(i8*) !dbg
+; CHECK: declare dso_local void @0(i8*)
+
+!llvm.dbg.cu = !{}
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!1 = distinct !DISubprogram(name: "bar", scope: !2, file: !2, line: 14, type: !3, scopeLine: 14, spFlags: DISPFlagDefinition, unit: !5)
+!2 = !DIFile(filename: "foo.c", directory: "/bar")
+!3 = !DISubroutineType(types: !4)
+!4 = !{}
+!5 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, producer: "My Compiler", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, nameTableKind: None)