[Bug rtl-optimization/64003] valgrind complains about get_attr_length_nobnd in insn-attrtab.c from i386.md

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64003

--- Comment #5 from dmalcolm at gcc dot gnu.org ---
Running valgrind with --track-origins=yes shows:
==9952==  Uninitialised value was created by a heap allocation
==9952==    at 0x4A0645D: malloc (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==9952==    by 0x12BF3B7: xmalloc (xmalloc.c:147)
==9952==    by 0x7876A4: shorten_branches(rtx_insn*) (final.c:1022)
==9952==    by 0x787F5F: (anonymous
namespace)::pass_shorten_branches::execute(function*) (final.c:4567)
==9952==    by 0x994581: execute_one_pass(opt_pass*) (passes.c:2269)
==9952==    by 0x994B95: execute_pass_list_1(opt_pass*) (passes.c:2321)
==9952==    by 0x994BA7: execute_pass_list_1(opt_pass*) (passes.c:2322)
==9952==    by 0x994BA7: execute_pass_list_1(opt_pass*) (passes.c:2322)
==9952==    by 0x994BE8: execute_pass_list(function*, opt_pass*)
(passes.c:2332)
==9952==    by 0x6B87E3: cgraph_node::expand() (cgraphunit.c:1773)
==9952==    by 0x6B9DB8: symbol_table::compile() (cgraphunit.c:1909)
==9952==    by 0x6BB69C: symbol_table::finalize_compilation_unit()
(cgraphunit.c:2325)

specifically, it's reading uninitialized data from the insn_lengths array
allocated here:
  insn_lengths = XNEWVEC (int, max_uid);