Re: [Bug] subword handling for DI modes

[Doug Evans <dje at transmeta dot com>]

Ben Elliston writes:
 > I wrote:
 > 
 >    Here is a minimal test case that reproduces the problem.  Does anyone
 >    have any ideas?  Thanks,
 > 
 >         (set reg (subword SI reg 0))
 > 
 > FYI, I was able to work around this by using:
 > 
 > 	(subword SI (reg h-reg) 0)
 > 
 > So it seems something is amiss in the determination of the operand's mode.

Here is my tentative proposed patch.

The bug happens when "compiling" the semantics of the insn.
semantic-compile will call rtx-traverse which will use the mode
of the result as the default mode for operand0.  subword is not a
normal rtx; the mode of operand0 is its own mode, not the mode of
the result of the rtx.

2000-10-26  Doug Evans  <dje@casey.transmeta.com>

	* rtx-funcs.scm (subword): Change mode spec of operand0 from OP0
	to ANY.

*** rtx-funcs.scm.~1~	Thu Jul 27 21:11:52 2000
--- rtx-funcs.scm	Thu Oct 26 21:49:11 2000
***************
*** 426,439 ****
  
  ; GCC's subreg.
  ; Called subword 'cus it's not exactly subreg.
! ; Word numbering is from most signficant (word 0) to least (word N-1).
  ; ??? May also want an endian dependent word ordering.  That can be
  ; implemented on top of or beside this.
  ; ??? GCC plans to switch to SUBREG_BYTE.  Keep an eye out for the switch
  ; (which is extensive so probably won't happen anytime soon).
  
  (drn (subword &options &mode value word-num)
!      (OPTIONS NUMMODE RTX RTX) (NA NA OP0 INT)
       ARG
       #f
  )
--- 426,444 ----
  
  ; GCC's subreg.
  ; Called subword 'cus it's not exactly subreg.
! ; Word numbering is from most significant (word 0) to least (word N-1).
  ; ??? May also want an endian dependent word ordering.  That can be
  ; implemented on top of or beside this.
  ; ??? GCC plans to switch to SUBREG_BYTE.  Keep an eye out for the switch
  ; (which is extensive so probably won't happen anytime soon).
+ ;
+ ; The mode spec of operand0 use to be OP0, but subword is not a normal rtx.
+ ; The mode of operand0 is not necessarily the same as the mode of the result,
+ ; and code which analyzes it would otherwise use the result mode (specified by
+ ; `&mode') for the mode of operand0.
  
  (drn (subword &options &mode value word-num)
!      (OPTIONS NUMMODE RTX RTX) (NA NA ANY INT)
       ARG
       #f
  )