[PATCH] D84630: [StackSafety] Skip ambiguous lifetime analysis

[Evgenii Stepanov via Phabricator via llvm-commits]

eugenis added inline comments.


================
Comment at: llvm/lib/Analysis/StackLifetime.cpp:301
+    case LivenessType::Must:
+      LiveRanges.resize(NumAllocas, LiveRange(Instructions.size()));
+      break;
----------------
vitalybuka wrote:
> t.p.northover wrote:
> > Doesn't this case need the loop below? It looks like it's undoing all the extra default initialization caused by the resize.
> > 
> > Actually, I'd be inclined to reword the whole thing in terms of resizing with the default and separately setting `NumAllocas - 1` if that is the correct reading.
> Loop below sets Full range for uninteresting allocas, however with HasUnknowLifetimeStartOrEnd we can't be sure which are uninteresting,
> Other than that I am not sure what are you asking.
I think Vitaly's right, if we see a lifetime that can't be traced back to an alloca, we have no way of knowing which allocas are "not interesting" and must handle all of them conservatively.


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  https://reviews.llvm.org/D84630/new/

https://reviews.llvm.org/D84630