[MLIR][LLVM] Avoid creating unused NameLocs for imported functions (llvm#163506)

This commit removes the creation of NameLocs when importing locations
for LLVM IR functions. This made the generated fused location more
complex by adding no valuable additional information to it. Note that
removing it has no effect on the roundtrip from LLVM IR back to LLVM IR.

Author: Dinistro

mlir/lib/Target/LLVMIR/DebugImporter.cpp

@@ -34,11 +34,9 @@ Location DebugImporter::translateFuncLocation(llvm::Function *func) {
     return UnknownLoc::get(context);
 
   // Add a fused location to link the subprogram information.
-  StringAttr funcName = StringAttr::get(context, subprogram->getName());
   StringAttr fileName = StringAttr::get(context, subprogram->getFilename());
   return FusedLocWith<DISubprogramAttr>::get(
-      {NameLoc::get(funcName),
-       FileLineColLoc::get(fileName, subprogram->getLine(), /*column=*/0)},
+      {FileLineColLoc::get(fileName, subprogram->getLine(), /*column=*/0)},
       translate(subprogram), context);
 }
 

mlir/test/Target/LLVMIR/Import/debug-info.ll

@@ -240,11 +240,10 @@ define void @subprogram() !dbg !3 {
 define void @func_loc() !dbg !3 {
   ret void
 }
-; CHECK-DAG: #[[NAME_LOC:.+]] = loc("func_loc")
 ; CHECK-DAG: #[[FILE_LOC:.+]] = loc("debug-info.ll":42:0)
 ; CHECK-DAG: #[[SP:.+]] =  #llvm.di_subprogram<id = distinct[{{.*}}]<>, compileUnit = #{{.*}}, scope = #{{.*}}, name = "func_loc", file = #{{.*}}, line = 42, subprogramFlags = Definition>
 
-; CHECK: loc(fused<#[[SP]]>[#[[NAME_LOC]], #[[FILE_LOC]]]
+; CHECK: loc(fused<#[[SP]]>[#[[FILE_LOC]]]
 
 !llvm.dbg.cu = !{!1}
 !llvm.module.flags = !{!0}