[AIX] Always pass namedsects option when linking with PGO.

[w2yehia]

Summary

Currently, we only pass the -bdbg:namedsects linker option when PGO is ON and LTO is OFF. That's because LTO does the merging of multiple sections of the same name into a single section, and so we don't need the linker option.
However, the input object files at link step could be a mix of LTO and non-LTO built objects, and so we should always specify the -bdbg:namedsects option when linking with PGO.

[jsji]

LGTM. Thanks.

clang/lib/Driver/ToolChains/AIX.cpp

if (Args.hasArg(options::OPT_static))
     CmdArgs.push_back("-bnso");
 
   // Add options for shared libraries.
   if (Args.hasArg(options::OPT_shared)) {
     CmdArgs.push_back("-bM:SRE");
     CmdArgs.push_back("-bnoentry");
   }
 
-  // Specify PGO linker option without LTO
-  if (!D.isUsingLTO() &&
-      (Args.hasFlag(options::OPT_fprofile_arcs, options::OPT_fno_profile_arcs,
+  // PGO instrumentation generates symbols belonging to special sections, and
+  // the linker needs to place all symbols in a particular section together in
+  // memory; the AIX linker does that under an option.
+  if (Args.hasFlag(options::OPT_fprofile_arcs, options::OPT_fno_profile_arcs,
                     false) ||
        Args.hasFlag(options::OPT_fprofile_generate,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasFlag(options::OPT_fprofile_generate_EQ,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasFlag(options::OPT_fprofile_instr_generate,
                     options::OPT_fno_profile_instr_generate, false) ||
        Args.hasFlag(options::OPT_fprofile_instr_generate_EQ,
                     options::OPT_fno_profile_instr_generate, false) ||
        Args.hasFlag(options::OPT_fcs_profile_generate,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasFlag(options::OPT_fcs_profile_generate_EQ,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasArg(options::OPT_fcreate_profile) ||
-       Args.hasArg(options::OPT_coverage)))
+       Args.hasArg(options::OPT_coverage))
     CmdArgs.push_back("-bdbg:namedsects");
 
   // Specify linker output file.
   assert((Output.isFilename() || Output.isNothing()) && "Invalid output.");
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());
   }

clang/test/Driver/aix-ld.c

 // RUN:        --sysroot %S/Inputs/aix_ppc_tree \
 // RUN:        --unwindlib=libunwind \
 // RUN:   | FileCheck --check-prefix=CHECK-PGO-LTO %s
 // CHECK-PGO-LTO-NOT: warning:
 // CHECK-PGO-LTO:     "-cc1" "-triple" "powerpc-ibm-aix7.2.5.3"
 // CHECK-PGO-LTO:     "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-PGO-LTO:     "-isysroot" "[[SYSROOT:[^"]+]]"
 // CHECK-PGO-LTO:     "{{.*}}ld{{(.exe)?}}"
-// CHECK-PGO-LTO-NOT: "-bdbg:namedsects"
+// CHECK-PGO-LTO:     "-bdbg:namedsects"
 // CHECK-PGO-LTO:     "-b32"
 // CHECK-PGO-LTO:     "-bpT:0x10000000" "-bpD:0x20000000"
 // CHECK-PGO-LTO:     "[[SYSROOT]]/usr/lib{{/|\\\\}}crt0.o"
 // CHECK-PGO-LTO-NOT: "-lc++"
 // CHECK-PGO-LTO-NOT: "-lc++abi"
 // CHECK-PGO-LTO:     "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}aix{{/|\\\\}}libclang_rt.builtins-powerpc.a"
 // CHECK-PGO-LTO-NOT: "--as-needed"
 // CHECK-PGO-LTO-NOT: "-lunwind"
 // CHECK-PGO-LTO-NOT: "--no-as-needed"
 // CHECK-PGO-LTO-NOT: "-lm"
 // CHECK-PGO-LTO:     "-lc"