On 10/31/14 02:07, Jan Beulich wrote:
While it always seemed wrong to me that there's no way to avoid the
default "flags" and "fpsr" clobbers, the regression the fix for
PR/60663 introduced (see PR/63637) makes it even more desirable to have
such a mechanism: This way, at least asm()s with a single output and no
explicit clobbers can again be made subject to CSE.
gcc:
2014-10-31 Jan Beulich <jbeul...@suse.com>
* config/i386/i386.c (ix86_target_string): Add
-mno-default-asm-clobbers.
(ix86_valid_target_attribute_inner_p): Handle
-m{,no-}default-asm-clobbers.
(ix86_md_asm_clobbers): Handle "inverse" clobbers.
* config/i386/i386.h (NOCC_REGNUM, NOFPSR_REGNUM): Define.
(ADDITIONAL_REGISTER_NAMES): Add "cc", "!cc", "!flags", and
"!fpsr".
* config/i386/i386.opt: Add mdefault-asm-clobbers and
mno-default-asm-clobbers.
* varasm.c (decode_reg_name_and_count): Permit negative
register numbers in ADDITIONAL_REGISTER_NAMES.
gcc/testsuite:
2014-10-31 Jan Beulich <jbeul...@suse.com>
* gcc.target/i386/20060218-1.c: Adjust expected error.
* gcc.target/i386/invclbr[123].c: New.
I really don't like having an option that's globally applied for this
feature. THough I am OK with having a mechanism to avoid implicit
clobbers on specific ASMs.
Why use negative numbers for the hard register numbers? I wouldn't be
at all surprised if lots of random code assumes register numbers are
always positive.
I don't like adding new registers with special names like !foo. Instead
I think that listing "!cc" or something similar in the asm itself if it
doesn't clobber the cc register would be better.
Other opinions?
jeff
