[PATCH] D15996: Avoid undefined behavior in LinkAllPasses.h

[Dimitry Andric via llvm-commits]

dim added inline comments.

================
Comment at: include/llvm/LinkAllPasses.h:198
@@ -192,1 +197,3 @@
+      } BRP(0);
+      (void) BRP.createPrinterPass(os, "");
       llvm::AliasSetTracker X(*(llvm::AliasAnalysis*)nullptr);
----------------
joker.eph wrote:
> Isn't instantiating a `RGPassManager` enough to force link `RegionPass.cpp`?
Well, this was already done in the original code, but then they tried to pass it as an argument to a call to `runOnRegion`.  I am unsure what this gained, and why the RGPassManager appears to be a little different than the other pass managers...

That said, I think such a local object cannot be optimized out, certainly because the constructor is not inlined.  The assembly shows:

        leal    72(%esp), %esi
        movl    %esi, (%esp)
        calll   llvm::RGPassManager::RGPassManager()@PLT

so it's indeed definitely being called.


http://reviews.llvm.org/D15996