Fix the bug that parseAAPipeline is not invoked in runNewPMPasses in release compiler.

[danielcdh]

Summary

The logic is guarded by "assert".

[davide]

this is a no brainer, but do you mind to add a test, if possible?

[chandlerc]

Doh! Agree with Davide about a test. I can try to conjure up one if it isn't easy...

[danielcdh]

Tried to add a test. But either need to have

1. a testcase that go through all default optimization pipeline, and make a difference with and without the default AA pipeline (tried test/Analysis/BasicAA/invariant_load.ll, but does not work)
2. introduce something like -debug-pass-manager to llvm-lto2 so that we can check for passes invoked by llvm-lto2

#2 is beyond the scope of this patch. So I plan to commit the patch as is. I could work on #2 later (maybe after I get AutoFDO + newPM performance back to normal).

Please let me know if the plan does not sound OK, otherwise I'll commit patch before I leave work today.

Thanks,
Dehao

[davide]

Wondering whether that should be a report_fatal_error instead of llvm_unreachable? (as I did in runNewPMCustomPasses).
[apologies if I'm missing something, I have this code out of cache and my head deep in GVN today].

Also, either 1) or 2) is fine. I'd prefer 2), and I'd really prefer this to be now. If it's too trouble, maybe open a PR and add a FIXME here.
I understand this is blocking a lot of people, so, if Chandler is OK, this can go in as is (with my previous comments addressed).

BTW, thanks for catching this braino!

[danielcdh]

Add test.

[danielcdh]

I've added the test. Please let me know if you want me to split the patch in 2.

Thanks,
Dehao

[davide]

LGTM. No need to split.

[chandlerc]

LGTM as well FWIW, but happy to defer to Davide here.

[davide]

Go for it, hopefully you can commit this today and unblock people :)

lib/LTO/LTOBackend.cpp

 }
 
 static void runNewPMPasses(Module &Mod, TargetMachine *TM, unsigned OptLevel,
                            bool IsThinLTO) {
   PassBuilder PB(TM);
   AAManager AA;
 
   // Parse a custom AA pipeline if asked to.
-  assert(PB.parseAAPipeline(AA, "default"));
+  if (!PB.parseAAPipeline(AA, "default"))
+    llvm_unreachable("Error parsing AA pipeline");
 
   LoopAnalysisManager LAM;
   FunctionAnalysisManager FAM;
   CGSCCAnalysisManager CGAM;
   ModuleAnalysisManager MAM;
 
   // Register the AA manager first so that our version is the one used.
   FAM.registerPass([&] { return std::move(AA); });