[Backport Ping][AArch64] PR target/20666, fix wrong encoding of new introduced BFC pseudo

[Jiong Wang <jiong dot wang at foss dot arm dot com>]

On 11/10/16 10:41, Richard Earnshaw (lists) wrote:
> On 10/10/16 17:40, Jiong Wang wrote:
> > On 24/11/15 11:17, Matthew Wahab wrote:
> > > opcodes/
> > > 2015-11-24  Matthew Wahab  <matthew.wahab@arm.com>
> > >
> > >      * aarch64-asm-2.c: Regenerate.
> > >      * aarch64-asm.c (convert_bfc_to_bfm): New.
> > There looks like a copy & paste error in this function, and caused PR
> > target/20666.
> >
> > +convert_bfc_to_bfm (aarch64_inst *inst)
> > +{
> > +  int64_t lsb, width;
> > +
> > +  /* Insert XZR.  */
> > +  copy_operand_info (inst, 3, 2);
> > +  copy_operand_info (inst, 2, 1);
> > +  copy_operand_info (inst, 2, 0);
> >                              ^~~~~~~ should be "0".
> >
> > "BFC Xd, lsb, width" is simplified form of "BFI Xd, XZR, lsb, width",
> > and both
> > are alias and will be transformed into "BFM Xd, XZR, immr, imms" during
> > encoding,
> > we inserting XZR into operand 1 of BFM, and the operand 0 (Xd) is not
> > changed.
> >
> > The expected results in the testcase are also wrong. Both fixed.
> >
> > OK for master?
> OK.  You'll need Tristan's ack for the backports, but as a wrong code
> bug I hope he'll approve.
>
> R.

Ping ~

Tristan, OK to backport?  This is an important wrong encoding fix.

I want to backport to 2.26 and 2.27.  Patch applies cleanly on both.

Thanks.