Re: RTL type checking and '0' format codes

[Jeffrey A Law <law at cygnus dot com>]

  In message <199908162310.QAA09148@zack.bitmover.com>you write:
  > 
  > I have been looking into implementing type checking for RTL, much like
  > the type checking for trees we already have.  The various XFOO
  > macros would check the slot against the format, and abort if it was
  > invalid.
Excellent!  We actually had someone working on this earlier, but we could never
get a copyright assignment for the work, so it never got integrated.

  > '0' format codes cause problems.  '0' is documented to mean that the
  > slot is only valid in a specific pass, and should be ignored
  > otherwise.  They aren't initialized in gen_rtx_FOO, and they're
  > ignored in generic copy-or-examine-RTL code.
Right.

  > Most '0' slots are always addressed with a specific type, but the
  > information on their type isn't in the format.  LABEL_NUSES,
  > JUMP_LABEL, LABEL_REFS, LABEL_NEXTREF, and CONTAINING_INSN are like
  > this.  We would like to type check them.
I'd punt initially and get the basic checking code installed.  Then return
to this issue.

jeff