[llvm] r205498 - Revert "[Constant Hoisting] Lazily compute the idom and cache the result."

[Juergen Ributzka]

Author: ributzka
Date: Wed Apr  2 20:38:47 2014
New Revision: 205498

URL: http://llvm.org/viewvc/llvm-project?rev=205498&view=rev
Log:
Revert "[Constant Hoisting] Lazily compute the idom and cache the result."

This code is no longer usefull, because we only compute and use the
IDom once. There is no benefit in caching it anymore.

Modified:
    llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp?rev=205498&r1=205497&r2=205498&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp Wed Apr  2 20:38:47 2014
@@ -87,10 +87,9 @@ struct ConstantCandidate {
 struct RebasedConstantInfo {
   ConstantUseListType Uses;
   Constant *Offset;
-  mutable BasicBlock *IDom;
 
   RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset)
-    : Uses(Uses), Offset(Offset), IDom(nullptr) { }
+    : Uses(Uses), Offset(Offset) { }
 };
 
 /// \brief A base constant and all its rebased constants.
@@ -151,17 +150,6 @@ private:
     Entry = nullptr;
   }
 
-  /// \brief Find the common dominator of all uses and cache the result for
-  /// future lookup.
-  BasicBlock *getIDom(const RebasedConstantInfo &RCI) const {
-    if (RCI.IDom)
-      return RCI.IDom;
-    RCI.IDom = findIDomOfAllUses(RCI.Uses);
-    assert(RCI.IDom && "Invalid IDom.");
-    return RCI.IDom;
-  }
-
-  BasicBlock *findIDomOfAllUses(const ConstantUseListType &Uses) const;
   Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const;
   Instruction *findConstantInsertionPoint(const ConstantInfo &ConstInfo) const;
   void collectConstantCandidates(ConstCandMapType &ConstCandMap,
@@ -214,32 +202,6 @@ bool ConstantHoisting::runOnFunction(Fun
   return MadeChange;
 }
 
-/// \brief Find nearest common dominator of all uses.
-/// FIXME: Replace this with NearestCommonDominator once it is in common code.
-BasicBlock *
-ConstantHoisting::findIDomOfAllUses(const ConstantUseListType &Uses) const {
-  // Collect all basic blocks.
-  SmallPtrSet<BasicBlock *, 8> BBs;
-  for (auto const &U : Uses)
-    BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
-
-  if (BBs.count(Entry))
-    return Entry;
-
-  while (BBs.size() >= 2) {
-    BasicBlock *BB, *BB1, *BB2;
-    BB1 = *BBs.begin();
-    BB2 = *std::next(BBs.begin());
-    BB = DT->findNearestCommonDominator(BB1, BB2);
-    if (BB == Entry)
-      return Entry;
-    BBs.erase(BB1);
-    BBs.erase(BB2);
-    BBs.insert(BB);
-  }
-  assert((BBs.size() == 1) && "Expected only one element.");
-  return *BBs.begin();
-}
 
 /// \brief Find the constant materialization insertion point.
 Instruction *ConstantHoisting::findMatInsertPt(Instruction *Inst,
@@ -262,12 +224,11 @@ Instruction *ConstantHoisting::findMatIn
 Instruction *ConstantHoisting::
 findConstantInsertionPoint(const ConstantInfo &ConstInfo) const {
   assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
-  // Collect all IDoms.
+  // Collect all basic blocks.
   SmallPtrSet<BasicBlock *, 8> BBs;
   for (auto const &RCI : ConstInfo.RebasedConstants)
-    BBs.insert(getIDom(RCI));
-
-  assert(!BBs.empty() && "No dominators!?");
+    for (auto const &U : RCI.Uses)
+      BBs.insert(U.Inst->getParent());
 
   if (BBs.count(Entry))
     return &Entry->front();