[Bug target/28115] New: possible bug in recog_memoized usage in rs6000.c??

["dkwan at transmeta dot com" <gcc-bugzilla at gcc dot gnu dot org>]

This problem is found by code inspection. The comment of the generated file
insn-recog.c says:

  `recog' contains a decision tree that recognizes whether the rtx
   X0 is a valid instruction.

   recog returns -1 if the rtx is not valid.  If the rtx is valid, recog
   returns a nonnegative number which is the insn code number for the
   pattern that matched.  This is the same as the order in the machine
   description of the entry that matched.  This number can be used as an
   index into `insn_data' and other tables.

recog_memoized() is just a wrapper around recog() to cache results.
In recog.h:

/* Try recognizing the instruction INSN,
   and return the code number that results.
   Remember the code so that repeated calls do not
   need to spend the time for actual rerecognition.

   This function is the normal interface to instruction recognition.
   The automatically-generated function `recog' is normally called
   through this one.  (The only exception is in combine.c.)  */

static inline int
recog_memoized (rtx insn)
{
  if (INSN_CODE (insn) < 0)
    INSN_CODE (insn) = recog (PATTERN (insn), insn, 0);
  return INSN_CODE (insn);
}

Yet in rs6000.c, there is code in rs6000_adjust_cost:

line 16312:
  if (! recog_memoized (insn))
    return 0;

line: 16355 
              && recog_memoized (dep_insn)
              && (INSN_CODE (dep_insn) >= 0)

These look as if it is assumed that recog_memoized return 0 for invalid
instructions but 0 is a valid result code. The checks should be done against
negative return values instead.


-- 
           Summary: possible bug in recog_memoized usage in rs6000.c??
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dkwan at transmeta dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28115