Hi all,

This patch fixes some fallout in the i386 testsuite that occurs after the simplification in patch [1/3] [1].
The gcc.target/i386/extract-2.c FAILs because it expects to match:
(set (reg:CC 17 flags)
     (compare:CC (subreg:QI (zero_extract:SI (reg:HI 98)
                 (const_int 8 [0x8])
                 (const_int 8 [0x8])) 0)
         (const_int 4 [0x4])))

which is the *cmpqi_ext_2 pattern in i386.md but with the new simplification the combine/simplify-rtx
machinery produces:
(set (reg:CC 17 flags)
     (compare:CC (subreg:QI (zero_extract:HI (reg:HI 98)
                 (const_int 8 [0x8])
                 (const_int 8 [0x8])) 0)
         (const_int 4 [0x4])))

Notice that the zero_extract now has HImode like the register source rather than SImode.
The existing *cmpqi_ext_<n> patterns however explicitly demand an SImode on the zero_extract.
I'm not overly familiar with the i386 port but I think that's too restrictive.
The RTL documentation says:
For (zero_extract:m loc size pos) "The mode m is the same as the mode that would be used for loc if it were a register."
I'm not sure if that means that the mode of the zero_extract and the source register must always match (as is the
case after patch [1/3]) but in any case it shouldn't matter semantically since we're taking a QImode subreg of the whole
thing anyway.

So the proposed solution in this patch is to allow HI, SI and DImode zero_extracts in these patterns as these are the
modes that the ext_register_operand predicate accepts, so that the patterns can match the new form above.

With this patch the aforementioned test passes again and bootstrap and testing on x86_64-unknown-linux-gnu shows
no regressions.

Is this ok for trunk if the first patch is accepted?

Thanks,
Kyrill

[1] https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00443.html

2018-02-07  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     PR target/84164
     * config/i386/i386.md (*cmpqi_ext_1): Rename to...
     (*cmpqi<mode>_ext_1): ... This.  Use SWI248 mode iterator
     for zero_extract.
     (*cmpqi_ext_2): Rename to...
     (*cmpqi<mode>_ext_2): ... This.  Use SWI248 mode iterator
     for zero_extract.
     (*cmpqi_ext_3): Rename to...
     (*cmpqi<mode>_ext_3): ... This.  Use SWI248 mode iterator
     for zero_extract.
     (*cmpqi_ext_4): Rename to...
     (*cmpqi<mode>_ext_4): ... This.  Use SWI248 mode iterator
     for zero_extract.