Hello!

Attached patch introduces generation of addr32 prefixed addresses,
mainly intended to merge ZERO_EXTRACTed LEA calculations into address.
 After fixing various inconsistencies with "o" constraints, the patch
works surprisingly well (in its current form fixes all reported
problems in the PR [1]), but one problem remains w.r.t. handling of
"o" constraint.

Patched gcc ICEs on gcc.dg/torture/pr47744-2.c with:

$ ~/gcc-build-fast/gcc/cc1 -O2 -mx32 -std=gnu99 -quiet pr47744-2.c
pr47744-2.c: In function ‘matmul_i16’:
pr47744-2.c:40:1: error: insn does not satisfy its constraints:
(insn 116 66 67 4 (set (reg:TI 0 ax)
        (mem:TI (zero_extend:DI (plus:SI (reg:SI 4 si [orig:114
ivtmp.26 ] [114])
                    (reg:SI 5 di [orig:101 dest_y ] [101]))) [6
MEM[base: dest_y_18, index: ivtmp.26_53, offset: 0B]+0 S16 A128]))
pr47744-2.c:34 60 {*movti_internal_rex64}
     (nil))
pr47744-2.c:40:1: internal compiler error: in
reload_cse_simplify_operands, at postreload.c:403
Please submit a full bug report,
...

... due to the fact that the address is not offsetable, and plus
((zero_extend (...)) (const_int ...)) gets rejected from
ix86_legitimate_address_p.

However, the section "16.8.1 Simple Constraints" of the documentation claims:

--quote--
   * A nonoffsettable memory reference can be reloaded by copying the
     address into a register.  So if the constraint uses the letter
     `o', all memory references are taken care of.
--/quote--

As I read this sentence, the RTX is forced into a temporary register,
and reload tries to satisfy "o" constraint with plus ((reg ...)
(const_int ...)), as said at the introduction of "o" constraint a
couple of pages earlier. Unfortunately, this does not seem to be the
case.

Is there anything wrong with my approach, or is there something wrong in reload?

2011-08-05  Uros Bizjak  <ubizjak@gmail.com>

	PR target/49781
	* config/i386/i386.c (ix86_decompose_address): Allow zero-extended
	SImode addresses.
	(ix86_print_operand_address): Handle zero-extended addresses.
	(memory_address_length): Add length of addr32 prefix for
	zero-extended addresses.
	* config/i386/predicates.md (lea_address_operand): Reject
	zero-extended operands.

Patch is otherwise bootstrapped and tested on x86_64-pc-linux-gnu
{,-m32} without regressions.

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49781

Thanks,
Uros.