[Bug tree-optimization/43402] New: dom1 miscompiles binary search

["matz at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

This actually happens in libicu, preventing genbrk (and hence openoffice and
texlive) to work.

# gcc -O1 icubug.c && ./a.out
Aborted

With -O0 it works.  The wrong transformation is done by dom1, it transforms
the loop into a linear sequence without backedges.

<bb 2>:
  goto <bb 8>;

<bb 3>:
  # start_16 = PHI <mid_25(5), start_21(8)>
  # limit_19 = PHI <limit_22(5), mid_25(8)>
  # lastMid_15 = PHI <mid_25(5), mid_25(8)>

<bb 4>:
  # start_1 = PHI <start_16(3)>
  # limit_2 = PHI <limit_19(3)>
  # lastMid_3 = PHI <mid_25(3)>
  D.2744_9 = start_1 + limit_2;
  mid_10 = D.2744_9 / 2;
  goto <bb 7>;

<bb 5>:
  if (result_14 > 0)
    goto <bb 3>;
  else
    goto <bb 6>;

<bb 6>:
  D.2754_17 = cnvNameType[mid_25].type;
  D.2753_18 = converterData[D.2754_17];

<bb 7>:
  # D.2753_4 = PHI <D.2753_18(6), 0B(4)>
  return D.2753_4;

<bb 8>:
  # start_21 = PHI <0(2)>
  # limit_22 = PHI <3(2)>
  # lastMid_23 = PHI <4294967295(2)>
  D.2744_24 = start_21 + limit_22;
  mid_25 = D.2744_24 / 2;
  D.2746_12 = cnvNameType[mid_25].name;
  result_14 = __builtin_strcmp (realName_13(D), D.2746_12);
  if (result_14 < 0)
    goto <bb 3>;
  else
    goto <bb 5>;


-- 
           Summary: dom1 miscompiles binary search
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: matz at gcc dot gnu dot org
  GCC host triplet: x86_64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43402