[Bug c/96597] New: valgrind error in do_hoist_insertion during O3 build

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96597

            Bug ID: 96597
           Summary: valgrind error in do_hoist_insertion during O3 build
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

==62146== Conditional jump or move depends on uninitialised value(s)
==62146==    at 0xD2A8FD: do_hoist_insertion (tree-ssa-pre.c:3581)
==62146==    by 0xD2A8FD: insert (tree-ssa-pre.c:3685)
==62146==    by 0xD2A8FD: (anonymous namespace)::pass_pre::execute(function*)
(tree-ssa-pre.c:4235)

tree-ssa-pre.c:3581 is

       && PRE_EXPR_REFERENCE (expr)->punned

Configure lines are

../trunk.git/configure --prefix=/home/dcb/gcc/results.20200812.valgrind \
        --disable-bootstrap \
        --disable-multilib \
        --disable-werror \
        --enable-checking=valgrind \
        --enable-languages=c,c++,fortran

sed 's/-O2/-O3/' < Makefile > Makefile.tmp
mv Makefile.tmp Makefile

valgrind is version 3.16.0 and valgrind is configured as follows:

$ more ~/.valgrind*
::::::::::::::
/home/dcb32B/.valgrindrc
::::::::::::::
--suppressions=/home/dcb32B/.valgrind.supp
--expensive-definedness-checks=yes
::::::::::::::
/home/dcb32B/.valgrind.supp
::::::::::::::

{
   bug1
   Memcheck:Cond
   fun:incorporate_penalties
}