[PATCH] D71217: Fix incorrect logic in maintaining the side-effect of compiler generated outliner functions

[Jessica Paquette via Phabricator via llvm-commits]

paquette added a comment.

> The outlined function in this test case does not serve the purpose since there are no live in registers. I did check this test case before. If I change the arguments 1, 2, 3, 4 to be incoming registers, the machine outliner won't kick in.

Maybe I'm misunderstanding something here?

(1) Locally, with the patch, adding

  liveins: $w0, $w1, $w2, $w3, $w4

does not change the outliner's behaviour.

(2) If I understand correctly, what you are trying to test here is that `implicit $xN` is added to the outlined call when `$xN` is not undefined in the outlined range.

Without this patch, this testcase produces

  BL @OUTLINED_FUNCTION_0, implicit-def $lr, implicit $sp, implicit-def $lr, implicit-def $w0, implicit-def $w1, implicit-def $w2, implicit-def $w3

With the patch, it adds `implicit $wzr, implicit $w4` at the end:

  BL @OUTLINED_FUNCTION_0, implicit-def $lr, implicit $sp, implicit-def $w3, implicit-def $w2, implicit-def $w1, implicit-def $w0, implicit-def $lr, implicit-def $w3, implicit-def $w2, implicit-def $w1, implicit-def $w0, implicit $sp, implicit $wzr, implicit $w4

It's kind of weird that the implicit defs are duplicated though. (`$lr` appears twice in both cases). I'd expect it to be

  BL @OUTLINED_FUNCTION_0, implicit-def $lr, implicit-def $w0, implicit-def $w1, implicit-def $w2, implicit-def $w3, implicit $sp, implicit $wzr, implicit $w4

Also, I guess it would also be good to add a testcase that ensures that a register is //not// added as implicit when it's undefined in the range.


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  https://reviews.llvm.org/D71217/new/

https://reviews.llvm.org/D71217