[LSR] don't attempt to promote ephemeral values to indvars

Summary:
This at least saves compile time. I also encountered a case where
ephemeral values affect whether other variables are promoted, causing
performance issues. It may be a bug in LSR, but I didn't manage to
reduce it yet. Anyhow, I believe it's in general not worth considering
ephemeral values in LSR.

Reviewers: atrick, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11115

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242011 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/IVUsers.h

@@ -21,6 +21,7 @@
 
 namespace llvm {
 
+class AssumptionCache;
 class DominatorTree;
 class Instruction;
 class Value;
@@ -119,15 +120,19 @@ private:
 class IVUsers : public LoopPass {
   friend class IVStrideUse;
   Loop *L;
+  AssumptionCache *AC;
   LoopInfo *LI;
   DominatorTree *DT;
   ScalarEvolution *SE;
-  SmallPtrSet<Instruction*,16> Processed;
+  SmallPtrSet<Instruction*, 16> Processed;
 
   /// IVUses - A list of all tracked IV uses of induction variable expressions
   /// we are interested in.
   ilist<IVStrideUse> IVUses;
 
+  // Ephemeral values used by @llvm.assume in this function.
+  SmallPtrSet<const Value *, 32> EphValues;
+
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
   bool runOnLoop(Loop *L, LPPassManager &LPM) override;