RFA: Switch on LRA on ARM (AArch32)

[Richard Earnshaw]

On 14/10/13 08:27, Yvan Roux wrote:
> Hi,
> 
> The status of LRA support for AArch32 is the sequel :
> - there is some regressions in the testsuite (gcc/g++, libstdc++ and
> fortran) in ARM mode, all due to the same neon legitimate address
> issue (tested in hard and softfp mode).
> - the compiler doesn't bootstrap with LRA enable for thumb (during
> libgcc build).
> 
> As stage 1 will be close soon, my first question is can we add the
> code to enable LRA before its ending, and fix the issues during stage
> 2 (according to Vladimir the legitimate address issue is mainly an LRA
> bugfix). The attached patch enables LRA by default but disable it for
> Thumb and let the opportunity to force LRA with -mlra, but maybe we
> can just turn it off by default.
> 
> I need your help for the Thumb issue, as suggested by Vladimir I
> disabled secondary reload for thumb (with the attached arm.h.diff
> patch) to let LRA deal with it and break a cycle, but I now face an
> issue exhibited by the attached testcase (thumb-lra.i) and the command
> line:
> 
> cc1 -O2 -mthumb -mlra thumb-lra.i
> 
> Here LRA as to deal with the thumb1_movhi_insn :
> 
> (insn 11 5 14 2 (set (reg:HI 0 r0)
>         (const_int -1318 [0xfffffffffffffada])) /work/tmp/t2.i:14 206
> {*thumb1_movhi_insn}
>      (nil))
> 
> and creates new regs to do it :
> 
>  11: r0:HI=r114:HI
>     Inserting insn reload before:
>  18: r115:SI=0xfffffffffffffada
>  19: r114:HI=r115:SI#0
>       REG_EQUAL 0xfffffffffffffada
> 
>  Choosing alt 6 in insn 18:  (0) l  (1) mi {*thumb1_movsi_insn}
>  Creating newreg=116 from oldreg=115, assigning class LO_REGS to r116
> 
>  18: r116:SI=0xfffffffffffffada
>     Inserting insn reload after:
>  20: r115:SI=r116:SI
> 
> Creating newreg=117, assigning class LO_REGS to scratch r117
> 
> and during this mov processing, we call gen_thumb_movhi_clobber which
> ICE because the first rtx parameter is not a strict memory address but
> a register, and here I'm not sure of what to do between fixing this in
> the backend or in LRA, and how to do it.
> 
> Thanks,
> Yvan=
> 
> 

I'd go with defaulting to LRA off until the regression has been
resolved.  You also need a ChangeLog entry.

OK with those done.

R.