[PATCH] D115406: [SystemZ] Improve eliminateFrameIndex() to use STDY/STEY/LDY for VR32/VR64 when possible.

Sat May 7 10:54:00 PDT 2022

jonpa added a comment.
Herald added a project: All.

This patch seems to have a much lesser impact now: In December last year this gave ~6000 less LAYs, and now only ~250 less. This seems to be due to the added ordering of the frame objects - if I disable that ordering I get some 6000 more LAYs in the output...

I ran the patch with and without the use of LEY and this time I did not see that it made any difference (earlier there was a regression with LEY). Now there are only a handful of extra LEYs emitted anyway...

I also made the experiment again with substituting all LEY:s with LAY+(LDE or LEY). In one build an LEY would result in LAY+LDE, and in another LAY+LEY. This would for all else the same, including alignments. In the "LEY build", the number LEYs went from 390 to 38, so most were gone. I could not see in any benchmark on either default or off that LEYs would be worse.

So overall, this seems to not give any noticable performance impact on SPEC to me. Given the above I would probably suggest putting back the LEY emission to the patch, or?

  "default fp-contract":

  lay            :                55499                55231     -268
  std            :                65122                64967     -155
  stdy           :                  865                 1020     +155
  ld             :                98755                98666      -89
  ldy            :                 3031                 3120      +89
  ste            :                51716                51698      -18
  stey           :                  286                  304      +18
  ley            :                  423                  429       +6
  lde            :                68442                68436       -6
  lg             :               976008               976007       -1
  stg            :               369621               369620       -1
  OPCDIFFS: -270

  Even less for some reason with "fp-contract off":

  lay            :                55247                55193      -54
  ...
  OPCDIFFS: -54

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115406/new/

https://reviews.llvm.org/D115406