The following compiler warning/error will be triggered when JVM is compiled with recent gcc compilers (>=7.3):

Compiling 395 files for BUILD_jdk.compiler.interim
In file included from /home/gromero/hg/jdk/jdk/src/hotspot/share/c1/c1_Compilation.hpp:29:0,
                 from /home/gromero/hg/jdk/jdk/src/hotspot/share/precompiled/precompiled.hpp:286:
/home/gromero/hg/jdk/jdk/src/hotspot/share/ci/ciMethodData.hpp: In member function ‘void LIR_Assembler::emit_typecheck_helper(LIR_OpTypeCheck*, Label*, Label*, Label*)’:
/home/gromero/hg/jdk/jdk/src/hotspot/share/ci/ciMethodData.hpp:595:100: warning: ‘data’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   int byte_offset_of_slot(ciProfileData* data, ByteSize slot_offset_in_data) { return in_bytes(offset_of_slot(data, slot_offset_in_data)); }
                                                                                            ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/gromero/hg/jdk/jdk/src/hotspot/cpu/ppc/c1_LIRAssembler_ppc.cpp:2400:18: note: ‘data’ was declared here
   ciProfileData* data;
                  ^~~~
In file included from /home/gromero/hg/jdk/jdk/src/hotspot/share/c1/c1_Compilation.hpp:29:0,
                 from /home/gromero/hg/jdk/jdk/src/hotspot/share/precompiled/precompiled.hpp:286:
/home/gromero/hg/jdk/jdk/src/hotspot/share/ci/ciMethodData.hpp:595:100: warning: ‘md’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   int byte_offset_of_slot(ciProfileData* data, ByteSize slot_offset_in_data) { return in_bytes(offset_of_slot(data, slot_offset_in_data)); }
                                                                                            ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/gromero/hg/jdk/jdk/src/hotspot/cpu/ppc/c1_LIRAssembler_ppc.cpp:2399:17: note: ‘md’ was declared here
   ciMethodData* md;
                 ^~


The following trivial fix will resolve the issue:

 @@ -141637,7 +141637,7 @@ void LIR_Assembler::emit_typecheck_helper(LIR_OpTypeCheck *op, Label* success, L
    }
  
    ciMethodData* md;
 - ciProfileData* data;
 + ciProfileData* data=0;
    int mdo_offset_bias = 0;
    if (should_profile) {
      ciMethod* method = op->profiled_method();