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Re: [PATCH], PowerPC support to enable -mlra and/or -mfloat128


On Tue, Jul 12, 2016 at 05:17:04PM +0200, Bernd Schmidt wrote:
> The Blackfin thing happens frequently with -fomit-frame-pointer when we have
> 
> (insn 66 64 70 8 (set (reg:SI 96 [ ivtmp.32 ])
>         (reg/f:SI 15 FP)) 19 {*movsi_insn}
> 
> Which LRA transforms to an invalid insn:
> 
> (insn 66 64 70 8 (set (reg:SI 15 FP [orig:96 ivtmp.32 ] [96])
>         (plus:SI (reg/f:SI 14 SP)
>             (const_int 4 [0x4]))) 50 {addsi3}
>      (expr_list:REG_EQUAL (reg/f:SI 15 FP)
>         (nil)))
> 
> Haven't fully debugged it but it looks like an instance of the same 
> problem: not using the correct register numbers in elimination. An FP+FP 
> addition would be fine (which is how I'm guessing we arrived at this 
> pattern), but once you substitute the real register number you get an 
> invalid insn. So LRA is somewhat defective in this area.

Do you have a testcase?  This sounds like fun :-)


Segher


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