LLVM default -mcpu setting inhibits customization
With GHC 8.4.1 we are now passing a default -mcpu selection to llvm. This default is passed regardless of any explicit command line option such as -optlc=-mcpu=native. If/when the user explicitly specifies the architecture we now get a failed build. The error message from LLVM is:
llc: for the -mcpu option: may only occur zero or one times!
`llc' failed in phase `LLVM Compiler'. (Exit code: 1)This is when compiling with GHC 8.4.1 as such:
{{{ ghc-8.4.1 -fforce-recomp -fllvm -optlc=-mcpu=native -O2 tt.hs }}
I suggest we either check for a user option of mcpu before adding the default or revert this behavior and allow llvm to take it's (optimistic and less portable) default.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.4.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (LLVM) |
| Test case | |
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