[Unroll] Replace a hand-wavy FIXME with a FIXME that explains the actual
problem instead of suggesting doing something that is trivial to do but
incorrect given the current design of the libraries.
llvm-svn: 237994
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index a5e5ffe..7bd1fcf 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -349,9 +349,14 @@
if (!SE.isSCEVable(V->getType()))
continue;
const SCEV *S = SE.getSCEV(V);
- // FIXME: Hoist the initialization out of the loop.
+
+ // FIXME: It'd be nice if the worklist and set used by the
+ // SCEVTraversal could be re-used between loop iterations, but the
+ // interface doesn't support that. There is no way to clear the visited
+ // sets between uses.
FindConstantPointers Visitor(&L, SE);
SCEVTraversal<FindConstantPointers> T(Visitor);
+
// Try to find (BaseAddress+Step+Offset) tuple.
// If succeeded, save it to the cache - it might help in folding
// loads.