PowerPC `rlwinm' codegen bug

[Todd Vierling <tv at pobox dot com>]

Before I state this bug report, I'd like to ask if there is a set of the
egcs 1.1.1 codegen bug patches out there in a nice li'l repository.  I have
seen codegen bug reports and patches go by, but until now, I didn't have a
reason to mind powerpc.

The following code snippet appears to generate bad code at the -O1
optimization level.  At -O0 the code seems fine.  I'm not a PowerPC expert,
but I can see from the data books that the generated assembly is bad (not to
mention thas gas bombs on the operand of `32').

Target configuration here is `powerpc-eabi'.  This happens with or without
haifa.

If the snippet looks familiar, it should be:  it's a simplified bit of stuff
from gcc/objc/sarray.h.  :)

=====
unsigned int
soffset_decode(unsigned int index)
{
  union {
    struct {
      unsigned int boffset : 16;
      unsigned int eoffset : 16;
    } off;
    unsigned int idx;
  } x;
  x.idx = index;
  return x.off.eoffset + (x.off.boffset * 32);
}
=====

The generated code with -O1:

=====
	.file	"sarray.i"
gcc2_compiled.:
	.section	".text"
	.align 2
	.globl soffset_decode
	.type	 soffset_decode,@function
soffset_decode:
	rlwinm 0,3,0,0xffff
	rlwinm 3,3,21,32,26		| this is the bad line (32)
	add 3,0,3
	blr
.Lfe1:
	.size	 soffset_decode,.Lfe1-soffset_decode
	.ident	"GCC: (GNU) egcs-2.91.60 19981201 (egcs-1.1.1 release)"
=====

The generated code with -O0:

=====
	.file	"sarray.i"
gcc2_compiled.:
	.section	".text"
	.align 2
	.globl soffset_decode
	.type	 soffset_decode,@function
soffset_decode:
	stwu 1,-32(1)
	stw 31,28(1)
	mr 31,1
	stw 3,8(31)
	lwz 0,8(31)
	stw 0,12(31)
	lhz 9,14(31)
	rlwinm 0,9,0,0xffff
	lhz 11,12(31)
	rlwinm 9,11,0,0xffff
	mr 11,9
	slwi 9,11,5
	add 0,0,9
	mr 3,0
	b .L1
.L1:
	lwz 11,0(1)
	lwz 31,-4(11)
	mr 1,11
	blr
.Lfe1:
	.size	 soffset_decode,.Lfe1-soffset_decode
	.ident	"GCC: (GNU) egcs-2.91.60 19981201 (egcs-1.1.1 release)"
=====

-- 
-- Todd Vierling (Personal tv@pobox.com; Bus. todd_vierling@xn.xerox.com)