ychen added inline comments.
================
Comment at: llvm/lib/Passes/PassBuilder.cpp:1659
+ bool DebugLogging) {
+ for (auto &C : PipelineStartEPCallbacks)
+ C(MPM);
----------------
asbirlea wrote:
> aeubanks wrote:
> > ychen wrote:
> > > What I have in mind is a newly added `O0EPCallbacks` field in PassBuilder
> > > class. Then we can keep existing EPCallbacks (including
> > > PipelineStartEPCallbacks) for >O0 optimization pipeline. Yeah, then you
> > > need to add related passes to O0EPCallbacks (for BPF in this case).
> > It's a tradeoff between having to specify required passes in both
> > O0EPCallbacks and PipelineStartEPCallbacks which is repetitive, versus
> > making all callbacks in PipelineStartEPCallbacks run at -O0, meaning even
> > optional passes in PipelineStartEPCallbacks will run at -O0 (may be skipped
> > via optnone).
> >
> > The legacy PM chooses the first, and I'm inclined to keep it that way just
> > for consistency.
> >
> > If we did go down the second route, we could just have a second
> > TargetMachine API like TargetMachine::addO0Passes() which directly adds
> > passes to a ModulePassManager.
> This seems more in line with the LPM behavior for O0.
> If BPF needs those passes even for O0 they should be added as such.
> It's a tradeoff between having to specify required passes in both
> O0EPCallbacks and PipelineStartEPCallbacks which is repetitive, versus making
> all callbacks in PipelineStartEPCallbacks run at -O0, meaning even optional
> passes in PipelineStartEPCallbacks will run at -O0 (may be skipped via
> optnone).
Indeed.
> The legacy PM chooses the first, and I'm inclined to keep it that way just
> for consistency.
I'm lost here. Do you mean to say the second?
> If we did go down the second route, we could just have a second TargetMachine
> API like TargetMachine::addO0Passes() which directly adds passes to a
> ModulePassManager.
Do you mean to say the first? This is not much different from adding to
O0EPCallbacks in TargetMachine::registerPassBuilderCallbacks.
My proposal to have both O0EPCallbacks and PipelineStartEPCallbacks is that I'm
not sure why we want to run all EP callbacks at O0. Do we have use cases for
that?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D89158/new/
https://reviews.llvm.org/D89158
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