[Bug middle-end/51986] New: [4.7 regression] uninitialized variable warning regression prevents bootstrap

[matt at use dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51986

             Bug #: 51986
           Summary: [4.7 regression] uninitialized variable warning
                    regression prevents bootstrap
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: matt@use.net


This just started in the last few days:

/tmp/gcc-obj/./prev-gcc/g++ -B/tmp/gcc-obj/./prev-gcc/
-B/home/matt/x86_64-unknown-linux-gnu/bin/ -nostdinc++
-B/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
-B/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs
-I/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu
-I/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include
-I/home/matt/src/gcc-4.7.0/libstdc++-v3/libsupc++
-L/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
-L/tmp/gcc-obj/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs -c  
-g -O2 -flto=jobserver -frandom-seed=1 -O2 -finline-functions -funswitch-loops
-fpredictive-commoning -fgcse-after-reload -ftree-vectorize -ffast-math
-floop-interchange -floop-strip-mine -floop-block -ftree-loop-distribution
-ftree-loop-distribute-patterns -ftree-loop-im -ftree-loop-ivcanon -fivopts
-fweb -DIN_GCC   -fno-exceptions -fno-rtti -W -Wall -Wno-narrowing
-Wwrite-strings -Wcast-qual -Wmissing-format-attribute -pedantic -Wno-long-long
-Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common 
-DHAVE_CONFIG_H -I. -I. -I/home/matt/src/gcc-4.7.0/gcc
-I/home/matt/src/gcc-4.7.0/gcc/. -I/home/matt/src/gcc-4.7.0/gcc/../include
-I/home/matt/src/gcc-4.7.0/gcc/../libcpp/include 
-I/home/matt/src/gcc-4.7.0/gcc/../libdecnumber
-I/home/matt/src/gcc-4.7.0/gcc/../libdecnumber/bid -I../libdecnumber   
/home/matt/src/gcc-4.7.0/gcc/sched-deps.c -o sched-deps.o
/home/matt/src/gcc-4.7.0/gcc/sched-deps.c: In function
‘sched_get_condition_with_rev(rtx_def const*, bool*)’:

/home/matt/src/gcc-4.7.0/gcc/sched-deps.c:599:33: error: ‘tmp’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]

Verified that it is a false positive, as
sched_get_condition_with_rev_uncached() always sets the contents of the bool in
question (if it isn't NULL, and it isn't in this case).

Can be reduced to -O2 -finline-functions, which probably isn't getting tested
much since using the bootstrap-O3 config has been broken for months now.

Pre-processed sources are attached.