[Bug c/66987] New: valgrind error in get_attr_length_nobnd

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66987

            Bug ID: 66987
           Summary: valgrind error in get_attr_length_nobnd
           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 today's (20150724) trunk code with valgrind
and got this

/home/dcb/gcc/working/./gcc/xgcc -B/home/dcb/gcc/working/./gcc/
-B/home/dcb/gcc/results/x86_64-unknown-linux-gnu/bin/
-B/home/dcb/gcc/results/x86_64-unknown-linux-gnu/lib/ -isystem
/home/dcb/gcc/results/x86_64-unknown-linux-gnu/include -isystem
/home/dcb/gcc/results/x86_64-unknown-linux-gnu/sys-include    -g -O2 -O2  -g
-O2 -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 _ashrdi3.o -MT _ashrdi3.o -MD -MP -MF _ashrdi3.dep
-DL_ashrdi3 -c ../../../src/trunk/libgcc/libgcc2.c -fvisibility=hidden
-DHIDE_EXPORTS
==31129== Conditional jump or move depends on uninitialised value(s)
==31129==    at 0xC95F36: get_attr_length_nobnd(rtx_insn*) (i386.md:6342)
==31129==    by 0xCA943A: insn_min_length(rtx_insn*) (i386.md:526)
==31129==    by 0x759F9F: shorten_branches(rtx_insn*) (final.c:1197)
==31129==    by 0x75A4DF: rest_of_handle_shorten_branches (final.c:4541)

i386.md:6342 is this

;; Subtract with jump on overflow.
(define_expand "subv<mode>4"
  [(parallel [(set (reg:CCO FLAGS_REG)
           (eq:CCO (minus:<DWI>
                  (sign_extend:<DWI>
                 (match_operand:SWI 1 "nonimmediate_operand"))

Configure line is

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