Amara Emerson 19ff00dab8 [AArch64] Fix CollectLOH creating an AdrpAdd LOH when there's a live used reg ...

between the two instructions.

If there's a pattern like:
$xA = ADRP foo @PAGE
[some killing use of reg Xb]
$Xb = ADDXri $Xa, 0, @PAGEOFF

CollectLOH would create an AdrpAdd LOH that resulted in the linker optimizing
this sequence into:
$xB = ADR foo
[some killing use of reg $Xb]
... and therefore clobbers the live $Xb register that was used by the
instruction in between.

This was discovered by a GlobalISel patch D78465 which broke up global variable
accesses into two pseudos, which in some cases could be moved apart.

Differential Revision: https://reviews.llvm.org/D80834

2020-06-01 16:00:55 -07:00

20 KiB

Raw Blame History

View Raw