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Teach instsimplify to gracefully degrade in the presence of instructions
not attched to a basic block or function. There are conservatively correct answers in these cases, and this makes the analysis more useful in contexts where we have a partially formed bit of IR. I don't have any way to test this directly... suggestions welcome here, but I'm not seeing anything sadly. I only found this using a subsequent patch to the inliner which runs instsimplify on partially inlined instructions, and even then only on a quite large program. I never got a reasonable testcase out of it, and anything I do get is likely to be quite fragile due to requiring an interaction of two different passes, and the only result being a segfault if it goes wrong. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153176 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -95,6 +95,12 @@ static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
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// Arguments and constants dominate all instructions.
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return true;
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// If we are processing instructions (and/or basic blocks) that have not been
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// fully added to a function, the parent nodes may still be null. Simply
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// return the conservative answer in these cases.
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if (!I->getParent() || !P->getParent() || !I->getParent()->getParent())
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return false;
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// If we have a DominatorTree then do a precise test.
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if (DT) {
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if (!DT->isReachableFromEntry(P->getParent()))
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