[Bug c/66420] New: valgrind error in improve_allocation

[Bug c/66420] New: valgrind error in improve_allocation

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66420

            Bug ID: 66420
           Summary: valgrind error in improve_allocation
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

I just tried a build of gcc trunk dated 2015063 with --enable-checking=valgrind
and got this

/home/dcb/gcc/working/./gcc/xgcc -B/home/dcb/gcc/working/./gcc/
-B/home/dcb/gcc/results.valgrind/x86_64-unknown-linux-gnu/bin/
-B/home/dcb/gcc/results.valgrind/x86_64-unknown-linux-gnu/lib/ -isystem
/home/dcb/gcc/results.valgrind/x86_64-unknown-linux-gnu/include -isystem
/home/dcb/gcc/results.valgrind/x86_64-unknown-linux-gnu/sys-include    -g -O3
-march=native -O2  -g -O3 -march=native -DIN_GCC    -W -Wall -Wno-narrowing
-Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes
-Wold-style-definition  -isystem ./include   -fpic -mlong-double-80
-DUSE_ELF_SYMVER -g -DIN_LIBGCC2 -fbuilding-libgcc -fno-stack-protector   -fpic
-mlong-double-80 -DUSE_ELF_SYMVER -I. -I. -I../.././gcc
-I../../../src/trunk/libgcc -I../../../src/trunk/libgcc/.
-I../../../src/trunk/libgcc/../gcc -I../../../src/trunk/libgcc/../include
-I../../../src/trunk/libgcc/config/libbid -DENABLE_DECIMAL_BID_FORMAT
-DHAVE_CC_TLS  -DUSE_TLS -o _ashldi3.o -MT _ashldi3.o -MD -MP -MF _ashldi3.dep
-DL_ashldi3 -c ../../../src/trunk/libgcc/libgcc2.c -fvisibility=hidden
-DHIDE_EXPORTS
==18793== Conditional jump or move depends on uninitialised value(s)
==18793==    at 0x91F4D4: improve_allocation() (ira-color.c:2780)
==18793==    by 0x9242B5: color_allocnos (ira-color.c:3104)
==18793==    by 0x9242B5: color_pass(ira_loop_tree_node*) (ira-color.c:3213)
==18793==    by 0x902158: ira_traverse_loop_tree(bool, ira_loop_tree_node*,
void (*)(ira_loop_tree_node*), void (*)(ira_loop_tree_node*))
(ira-build.c:1795)

Configure line is

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

and just to spice things up a bit I also did this:

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

The same problem didn't seem to occur when I dropped back from -O3
-march=native to -O2.

Machine type is AMD Phenom