[Bug rtl-optimization/72831] New: [7 Regression] Conditional jump or move depends on uninitialised value: regno_in_use_p (lra-spills.c:701)

["trippels at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72831

            Bug ID: 72831
           Summary: [7 Regression] Conditional jump or move depends on
                    uninitialised value: regno_in_use_p (lra-spills.c:701)
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
                CC: vmakarov at gcc dot gnu.org
  Target Milestone: ---

--enable-checking=valgrind on pcc64le shows:

==25092== Conditional jump or move depends on uninitialised value(s)
==25092==    at 0x1054EDCC: regno_in_use_p (lra-spills.c:701)
==25092==    by 0x1054EDCC: lra_final_code_change() (lra-spills.c:769)
==25092==    by 0x10525CFF: lra(_IO_FILE*) (lra.c:2482)
==25092==    by 0x104D159F: do_reload (ira.c:5384)
==25092==    by 0x104D159F: (anonymous
namespace)::pass_reload::execute(function*) (ira.c:5568)
==25092==    by 0x105D5E6B: execute_one_pass(opt_pass*) (passes.c:2344)
==25092==    by 0x105D64B7: execute_pass_list_1(opt_pass*) (passes.c:2428)
==25092==    by 0x105D64CF: execute_pass_list_1(opt_pass*) (passes.c:2429)
==25092==    by 0x105D657B: execute_pass_list(function*, opt_pass*)
(passes.c:2439)
==25092==    by 0x102A5453: cgraph_node::expand() (cgraphunit.c:1985)
==25092==    by 0x102A7057: expand_all_functions (cgraphunit.c:2121)
==25092==    by 0x102A7057: symbol_table::compile() (cgraphunit.c:2479)
==25092==    by 0x102A8F2B: symbol_table::finalize_compilation_unit()
(cgraphunit.c:2569)
==25092==    by 0x106C18D7: compile_file() (toplev.c:490)
==25092==    by 0x1012E99F: do_compile (toplev.c:1998)
==25092==    by 0x1012E99F: toplev::main(int, char**) (toplev.c:2132)
==25092==

It happens a lot when building libgcc.