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Add a comment about why ScalarEvolution doesn't recognize non-loop PHIs
even when they're obvious. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75632 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2402,6 +2402,10 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
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return SymbolicName;
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return SymbolicName;
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}
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}
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// It's tempting to recognize PHIs with a unique incoming value, however
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// this leads passes like indvars to break LCSSA form. Fortunately, such
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// PHIs are rare, as instcombine zaps them.
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// If it's not a loop phi, we can't handle it yet.
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// If it's not a loop phi, we can't handle it yet.
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return getUnknown(PN);
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return getUnknown(PN);
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}
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}
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