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

[dmalcolm at gcc dot gnu.org]

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

--- Comment #10 from dmalcolm at gcc dot gnu.org ---
Created attachment 34167
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34167&action=edit
Log from gdb session, with a conditional breakpoint to trap uninitialized reads

This is a log of a gdb session debugging cc1 compiling the reproducer from
comment #7, using the instrumentation patch from comment #8.

I put a breakpoint on:
  fancy_element::operator int () const
with condition that result == 0xabababab to handle reads of uninitialized
elements from insn_lengths[].

I took a backtrace both times that the conditional breakpoint occurred.