Re: [PATCH][GCC 7] Remove broken path in extract_bit_field_1

[Richard Biener <rguenther@suse.de>]

On Mon, 4 Apr 2016, Jakub Jelinek wrote:

> On Mon, Apr 04, 2016 at 02:56:51PM +0200, Richard Biener wrote:
> > The testcase gcc.target/i386/pr37870.c will already ICE with that
> > patch, so no additional testcase.
> 
> In theory you could validate_subreg first and use that code if validation
> went ok, otherwise go through memory.
> But I admit I don't have anything in particular in mind where it would
> trigger this code and the subreg would successfully validate.

Not sure if it would help as that has

  /* ??? Similarly, e.g. with (subreg:DF (reg:TI)).  Though 
store_bit_field
     is the culprit here, and not the backends.  */
  else if (osize >= UNITS_PER_WORD && isize >= osize)
    ;

and thus we'd return true anyway for (subreg:XF (reg:TI) 0)

Richard.

> > 2016-04-04  Richard Biener  <rguenther@suse.de>
> > 
> > 	PR middle-end/37870
> > 	* expmed.c (extract_bit_field_1): Remove broken case
> > 	using a wider MODE_INT mode.
> > 
> > Index: gcc/expmed.c
> > ===================================================================
> > --- gcc/expmed.c	(revision 234708)
> > +++ gcc/expmed.c	(working copy)
> > @@ -1647,17 +1647,6 @@ extract_bit_field_1 (rtx str_rtx, unsign
> >  	    if (GET_CODE (op0) == SUBREG)
> >  	      op0 = force_reg (imode, op0);
> >  	  }
> > -	else if (REG_P (op0))
> > -	  {
> > -	    rtx reg, subreg;
> > -	    imode = smallest_mode_for_size (GET_MODE_BITSIZE (GET_MODE (op0)),
> > -					    MODE_INT);
> > -	    reg = gen_reg_rtx (imode);
> > -	    subreg = gen_lowpart_SUBREG (GET_MODE (op0), reg);
> > -	    emit_move_insn (subreg, op0);
> > -	    op0 = reg;
> > -	    bitnum += SUBREG_BYTE (subreg) * BITS_PER_UNIT;
> > -	  }
> >  	else
> >  	  {
> >  	    HOST_WIDE_INT size = GET_MODE_SIZE (GET_MODE (op0));
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
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