https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59124
--- Comment #21 from baoshan <pangbw at gmail dot com> --- (In reply to Manuel López-Ibáñez from comment #20) > (In reply to baoshan from comment #19) > > We can see the value of up_sub is represented as unsigned int value > > 4294967291 which is really weird to me, it suppose to be a int value -5 > > here. > > All counters are unsigned. You can see what code looks like to GCC at > exactly that moment by using -fdump-tree-all-all-lineno and looking for that > line in test.c.079t.vrp1. > > ;; basic block 10, loop depth 1, count 0, freq 1430, maybe hot > ;; Invalid sum of incoming frequencies 1226, should be 1430 > ;; prev block 9, next block 11, flags: (NEW, REACHABLE) > ;; pred: 9 [85.7%] (TRUE_VALUE,EXECUTABLE) > ;; starting at line 9 > [test.c:9:13] # RANGE [4294967291, 4294967295] > _51 = i_2 + 4294967290; > [test.c:9:10] # RANGE [4294967291, 4294967295] NONZERO 4294967295 > _52 = (long unsigned intD.10) _51; > [test.c:9:10] # RANGE [17179869164, 17179869180] NONZERO 17179869180 > _53 = _52 * 4; > [test.c:9:10] # PT = nonlocal > _54 = bar_12(D) + _53; > [test.c:9:23] # VUSE <.MEM_48> > _55 = [test.c:9:23] bazD.1755[_51]; > [test.c:9:18] # .MEM_56 = VDEF <.MEM_48> > [test.c:9:10] *_54 = _55; > [test.c:9:13] # RANGE [4294967290, 4294967294] > _59 = i_2 + 4294967289; > [test.c:9:10] # RANGE [4294967290, 4294967294] NONZERO 4294967295 > _60 = (long unsigned intD.10) _59; > [test.c:9:10] # RANGE [17179869160, 17179869176] NONZERO 17179869180 > _61 = _60 * 4; > [test.c:9:10] # PT = nonlocal > _62 = bar_12(D) + _61; > [test.c:9:23] # VUSE <.MEM_56> > _63 = [test.c:9:23] bazD.1755[_59]; > [test.c:9:18] # .MEM_64 = VDEF <.MEM_56> > [test.c:9:10] *_62 = _63; > ;; succ: 11 [100.0%] (FALLTHRU,EXECUTABLE) > > It seems GCC at some moment unrolls the loop and creates such block with > those ranges. Probably, the block is unreachable, but it would be better to > not create it in the first place. Finding out where and why it is created > would help to figure out a fix. Don't you think the range value is strange? how it is possible the range value is so big according the code?
