[llvm-dev] Interaction of --disable-llvm-passes and -O0

David Blaikie via llvm-dev llvm-dev at lists.llvm.org
Fri Dec 15 10:28:57 PST 2017


do you have a specific (reduced, ideally) example of -O0
--disable-llvm-passes still running passes? I'd certainly expect -O0
without --disable-llvm-passes to run passes (things like the AlwaysInliner,
since respecting __attribute__((always_inline)) is necessary for program
correctness, even at -O0), but would be surprised if disabling llvm passes
didn't do what it says.

On Fri, Dec 15, 2017 at 12:01 AM Dan Zimmerman via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Pardon if this isn't the right forum for this question, but is there a
> reason that when both `--disable-llvm-passes` and `-O0` are passed to cc1
> llvm optimization passes still appear to occur? For the past hour or so I
> was trying to figure out how to get a proper test for
> https://reviews.llvm.org/D41050 out - as soon as I changed -O0 to -O3 (as
> suggested in this post:
> http://lists.llvm.org/pipermail/llvm-dev/2017-April/111989.html) the
> optimization passes didn't occur. Is this known/defined behavior? If so, is
> there documentation as to why it behaves that way?
>
> Dan
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> llvm-dev at lists.llvm.org
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