Revert "[SCEV] Do not fold dominated SCEVUnknown into AddRecExpr start"

This reverts commit r303730 because it broke all the buildbots.

llvm-svn: 303747

1 files changed, 2 insertions, 59 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 584419c1df3..78ded8141c0 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -2178,63 +2178,6 @@ StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
   return Flags;
 }
 
-bool ScalarEvolution::isAvailableAtLoopEntry(const SCEV *S, const Loop *L,
-                                             DominatorTree &DT, LoopInfo &LI) {
-  if (!isLoopInvariant(S, L))
-    return false;
-  // If a value depends on a SCEVUnknown which is defined after the loop, we
-  // conservatively assume that we cannot calculate it at the loop's entry.
-  struct FindDominatedSCEVUnknown {
-    bool Found = false;
-    const Loop *L;
-    DominatorTree &DT;
-    LoopInfo &LI;
-
-    FindDominatedSCEVUnknown(const Loop *L, DominatorTree &DT, LoopInfo &LI)
-        : L(L), DT(DT), LI(LI) {}
-
-    bool checkSCEVUnknown(const SCEVUnknown *SU) {
-      if (auto *I = dyn_cast<Instruction>(SU->getValue())) {
-        if (DT.dominates(L->getHeader(), I->getParent()))
-          Found = true;
-        else
-          assert(DT.dominates(I->getParent(), L->getHeader()) &&
-                 "No dominance relationship between SCEV and loop?");
-      }
-      return false;
-    }
-
-    bool follow(const SCEV *S) {
-      switch (static_cast<SCEVTypes>(S->getSCEVType())) {
-      case scConstant:
-        return false;
-      case scAddRecExpr:
-      case scTruncate:
-      case scZeroExtend:
-      case scSignExtend:
-      case scAddExpr:
-      case scMulExpr:
-      case scUMaxExpr:
-      case scSMaxExpr:
-      case scUDivExpr:
-        return true;
-      case scUnknown:
-        return checkSCEVUnknown(cast<SCEVUnknown>(S));
-      case scCouldNotCompute:
-        llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
-      }
-      return false;
-    }
-
-    bool isDone() { return Found; }
-  };
-
-  FindDominatedSCEVUnknown FSU(L, DT, LI);
-  SCEVTraversal<FindDominatedSCEVUnknown> ST(FSU);
-  ST.visitAll(S);
-  return !FSU.Found;
-}
-
 /// Get a canonical add expression, or something simpler if possible.
 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
                                         SCEV::NoWrapFlags Flags,
@@ -2516,7 +2459,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
     const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
     const Loop *AddRecLoop = AddRec->getLoop();
     for (unsigned i = 0, e = Ops.size(); i != e; ++i)
-      if (isAvailableAtLoopEntry(Ops[i], AddRecLoop, DT, LI)) {
+      if (isLoopInvariant(Ops[i], AddRecLoop)) {
         LIOps.push_back(Ops[i]);
         Ops.erase(Ops.begin()+i);
         --i; --e;
@@ -2791,7 +2734,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
     const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
     const Loop *AddRecLoop = AddRec->getLoop();
     for (unsigned i = 0, e = Ops.size(); i != e; ++i)
-      if (isAvailableAtLoopEntry(Ops[i], AddRecLoop, DT, LI)) {
+      if (isLoopInvariant(Ops[i], AddRecLoop)) {
         LIOps.push_back(Ops[i]);
         Ops.erase(Ops.begin()+i);
         --i; --e;