Debug Info: Mark os_log helper functions as artificial

[aprantl]

Summary

The os_log helper functions are linkonce_odr and supposed to be uniqued across TUs, so attachine a DW_AT_decl_line on it is highly misleading. By setting the function decl to implicit, CGDebugInfo properly marks the functions as artificial and uses a default file / line 0 location for the function.

rdar://problem/63450824

[vsk]

Thanks, lgtm!

clang/lib/CodeGen/CGBuiltin.cpp

   if (CGM.getCodeGenOpts().OptimizeSize == 2)
     Fn->addFnAttr(llvm::Attribute::NoInline);
 
   auto NL = ApplyDebugLocation::CreateEmpty(*this);
   IdentifierInfo *II = &Ctx.Idents.get(Name);
   FunctionDecl *FD = FunctionDecl::Create(
       Ctx, Ctx.getTranslationUnitDecl(), SourceLocation(), SourceLocation(), II,
       FuncionTy, nullptr, SC_PrivateExtern, false, false);
+  // Avoid generating debug location info for the function.
+  FD->setImplicit();
 
   StartFunction(FD, ReturnTy, Fn, FI, Args);
 
   // Create a scope with an artificial location for the body of this function.
   auto AL = ApplyDebugLocation::CreateArtificial(*this);
 
   CharUnits Offset;
   Address BufAddr(Builder.CreateLoad(GetAddrOfLocalVar(Args[0]), "buf"),

clang/test/CodeGen/debug-info-oslog.c

+// RUN: %clang_cc1 -triple x86_64-darwin-apple -debug-info-kind=limited \
+// RUN:   %s -emit-llvm -o -  | FileCheck %s
+void test_builtin_os_log(void *buf, int i, const char *data) {
+  __builtin_os_log_format(buf, "%d", i);
+}
+
+// CHECK: define linkonce_odr {{.*}}@__os_log_helper_1_0_1_4_0(
+// CHECK-SAME:   !dbg ![[OS_LOG_HELPER:[0-9]+]]
+
+// This helper is going to be uniqued, so it should not have a line
+// number between file and type.
+
+// CHECK: distinct !DISubprogram(name: "__os_log_helper_1_0_1_4_0",
+// CHECK-SAME:                   file: !{{[0-9+]}}, type
+// CHECK-SAME:                   flags: DIFlagArtificial