Remove false dependency on the destination of the popcnt instruction
fryguybob writes in D3539,
Some Intel processors appear to have a false dependency on the destination of the popcnt instruction. This could lead to poor performance. A simple way to prevent this is to clear the destination register immediately before the popcnt instruction. Currently I can't produce code from GHC where the source and destination registers are not the same (perhaps someone is interested in producing a test case that does). I'm putting this here in case anyone is interested in investigating further.
I'm opening this ticket so I can bump the diff out of the review queue, in hopes that someone might some day pick it up.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.0.1 |
| Type | FeatureRequest |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
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| Blocking | |
| CC | |
| Operating system | |
| Architecture |