Re: [PATCH, i386]: Rewrite LEA handling (was:Re: PATCH [10/n] X32: Support x32 LEA insns)

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Jul 25, 2011 at 5:33 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Mon, Jul 25, 2011 at 3:58 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>
>>> You are not fixing the core of the problem... this is why you need so
>>> much hacks and kludges at various places (some w.r.t. -fPIC already
>>> existed, see the patch). Above, you correctly identified the problem,
>>> so let's avoid gen_lowpart on SImode operands by not calling it
>>> anymore.
>>>
>>> Attached patch effectively rewrites LEA handling. The trick is, that
>>> instead of using Pmode operations in addresses, we use either SImode
>>> or DImode operations to calculate the address on 64bit targets. Up to
>>> now, address calculations strictly used Pmode, so SImode on 32bit
>>> targets and DImode on 64bit targets. Recent patches to
>>> ix86_decompose_address and ix86_legitimate_address_p relaxed this
>>> requirement.
>>>
>>> Attached patch changes LEA patterns and LEA splitters to accept
>>> addresses, calculated with either SImode or DImode operations.This
>>> means, that on x64 targets, we don't use gen_lowpart on SImode
>>> operands anymore. Since symbol references on x32 are in SImode, this
>>> solves the problem. The patch also avoids generating SImode subregs of
>>> DImode addresses and DImode zero_extends of SImode addresses, since
>>> LEA insn does this for us automatically.
>>>
>>> Please also note the change to ix86_print_operand_address. To avoid
>>> addr32 prefixes, we can force registers in DImode on 64bit targets
>>> without any problems. On x32, we can investigate, if this change
>>> avoids unnecessary LEAs (for PR 49781, patched gcc genrates 6 vs. 8).
>>
>> The testcase won't compile since PIC doesn't work:
>
> Well, I did say that -fPIC did not work.
>
>>> Patch was bootstrapped and regression tested on x86_64-pc-linux-gnu
>>> {,-m32} with no regressions. H.J., can you please test it on x32?
>>
>> On x32, it failed:
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49832
>>
>>> BTW: -fPIC is not yet implemented on trunk and still fails there with
>>> an (unrelated) error, I didn't check x32 branch.
>>>
>>
>> This could be:
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49833
>
> Attached patch implements -fpic handling for x32. In x32 mode, we now
> use x86_64_general_operand and corresponding "e" constraints for adds
> in SImode, since it looks that invalid addresses can only be generated
> through adds. This avoids a whole bunch of new predicates and
> constraints.
>
> 2011-07-25 ?Uros Bizjak ?<ubizjak@gmail.com>
>
> ? ? ? ?PR target/47381
> ? ? ? ?PR target/49832
> ? ? ? ?PR target/49833
> ? ? ? ?* config/i386/i386.md (add_operand): New mode attribute.
> ? ? ? ?(*movdi_internal_rex64): Remove mode from pic_32bit_operand check.
> ? ? ? ?(*movsi_internal): Ditto. ?Use "e" constraint in alternative 2.
> ? ? ? ?(*lea_1): Use SWI48 mode iterator.
> ? ? ? ?(*lea_1_zext): New insn pattern.
> ? ? ? ?(add<mode>3): Use <add_operand> predicate for operand 2.
> ? ? ? ?(*add<mode>_1): Use <add_operand> predicate for operand 2. ?Use "le"
> ? ? ? ?constraint for alternative 2.
> ? ? ? ?(addsi_1_zext): Use addsi_operand predicate for operand 2. ?Use "le"
> ? ? ? ?constraint for alternative 2.
> ? ? ? ?(add->lea splitter): Check operand modes in insn constraint. ?Extend
> ? ? ? ?operands less than SImode wide to SImode.
> ? ? ? ?(add->lea zext splitter): Do not extend operands to DImode.
> ? ? ? ?(*lea_general_1): Handle only QImode and HImode operands.
> ? ? ? ?(*lea_general_2): Ditto.
> ? ? ? ?(*lea_general_3): Ditto.
> ? ? ? ?(*lea_general_1_zext): Remove.
> ? ? ? ?(*lea_general_2_zext): Ditto.
> ? ? ? ?(*lea_general_3_zext): Ditto.
> ? ? ? ?(*lea_general_4): Check operand modes in insn constraint. ?Extend
> ? ? ? ?operands less than SImode wide to SImode.
> ? ? ? ?(ashift->lea splitter): Ditto.
> ? ? ? ?* config/i386/i386.c (ix86_print_operand_address): Print address
> ? ? ? ?registers with 'q' modifier on 64bit targets.
> ? ? ? ?* config/i386/predicates.md (pic_32bit_opreand): Define as special
> ? ? ? ?predicate. ?Reject non-SI and non-DI modes.
> ? ? ? ?(addsi_operand): New predicate.
>
> Uros.
>

X32 glibc is miscompiled:

CPP='/export/build/gnu/gcc-x32/release/usr/gcc-4.7.0-x32/bin/gcc -mx32
 -E -x c-header'
/export/build/gnu/glibc-x32/build-x86_64-linux/elf/ld-linux-x32.so.2
--library-path /export/build/gnu/glibc-x32/build-x86_64-linux:/export/build/gnu/glibc-x32/build-x86_64-linux/math:/export/build/gnu/glibc-x32/build-x86_64-linux/elf:/export/build/gnu/glibc-x32/build-x86_64-linux/dlfcn:/export/build/gnu/glibc-x32/build-x86_64-linux/nss:/export/build/gnu/glibc-x32/build-x86_64-linux/nis:/export/build/gnu/glibc-x32/build-x86_64-linux/rt:/export/build/gnu/glibc-x32/build-x86_64-linux/resolv:/export/build/gnu/glibc-x32/build-x86_64-linux/crypt:/export/build/gnu/glibc-x32/build-x86_64-linux/nptl
/export/build/gnu/glibc-x32/build-x86_64-linux/sunrpc/rpcgen -Y
../scripts -h rpcsvc/yppasswd.x -o
/export/build/gnu/glibc-x32/build-x86_64-linux/sunrpc/rpcsvc/yppasswd.T
make[5]: *** [/export/build/gnu/glibc-x32/build-x86_64-linux/sunrpc/rpcsvc/yppasswd.stmp]
Segmentation fault (core dumped)

Some LEA patterns are wrong for x32.  I will investigate.


-- 
H.J.