[PATCH] D110751: [DomTree] Assert that blocks in queries aren't from another function

[Daniil Suchkov via Phabricator via llvm-commits]

DaniilSuchkov created this revision.
DaniilSuchkov added reviewers: asbirlea, MaskRay.
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This assertion should help us catch cases when DT is used in a way that doesn't make much sense and usually indicates usage errors. In the attached testcase you can see the result of incorrect usage of DT. When processing `foo` SimpleLoopUnswitch decided to make `dominates(BB1, BB2)` query with BB2 being a block from another function (`bar`). In that case the result of the query was `true` since B isn't reachable from `foo`'s entry, so SimpleLoopUnswitch went ahead and replaced the use of `true` in `bar` because the preheader of one of the loops from `foo` "dominates" the entry block from `bar`.

I decided to add this assertion to `getNode` since all queries seem to be routed through that function for all non-trivial cases.


https://reviews.llvm.org/D110751

Files:
  llvm/include/llvm/Support/GenericDomTree.h
  llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-invariant-select-bug.ll


Index: llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-invariant-select-bug.ll
===================================================================
--- llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-invariant-select-bug.ll
+++ llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-invariant-select-bug.ll
@@ -1,4 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; REQUIRES: asserts
+; XFAIL: *
 ; RUN: opt -passes='simple-loop-unswitch<nontrivial>' -S < %s | FileCheck %s
 
 ; FIXME: We should not replace `true` with `false` here!
Index: llvm/include/llvm/Support/GenericDomTree.h
===================================================================
--- llvm/include/llvm/Support/GenericDomTree.h
+++ llvm/include/llvm/Support/GenericDomTree.h
@@ -349,6 +349,9 @@
   /// may (but is not required to) be null for a forward (backwards)
   /// statically unreachable block.
   DomTreeNodeBase<NodeT> *getNode(const NodeT *BB) const {
+    assert((!BB || !BB->getParent() || BB->getParent() == Parent) &&
+           "A node from another function!");
+
     auto I = DomTreeNodes.find(BB);
     if (I != DomTreeNodes.end())
       return I->second.get();


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