Commit 11405dfa authored by Tanya Lattner's avatar Tanya Lattner
Browse files

Merge 64579 from mainline. 

Fix pr3571: If stride is a value defined by an instruction, make sure it dominates the loop preheader. When IV users are strength reduced, the stride is inserted into the preheader. It could create a use before def situation.

llvm-svn: 64789
parent bc5b640c

llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp

+15 −3
Original line number Diff line number Diff line
@@ -400,7 +400,7 @@ static bool containsAddRecFromDifferentLoop(SCEVHandle S, Loop *L) { 
/// outer loop of the current loop.

static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,

                                  SCEVHandle &Start, SCEVHandle &Stride,

                                  ScalarEvolution *SE) {

                                  ScalarEvolution *SE, DominatorTree *DT) {

  SCEVHandle TheAddRec = Start;   // Initialize to zero.



  // If the outer level is an AddExpr, the operands are all start values except
@@ -437,9 +437,21 @@ static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L, 


  Start = SE->getAddExpr(Start, AddRec->getOperand(0));

  

  if (!isa<SCEVConstant>(AddRec->getOperand(1)))

  if (!isa<SCEVConstant>(AddRec->getOperand(1))) {

    // If stride is an instruction, make sure it dominates the loop header.

    // Otherwise we could end up with a use before def situation.

    if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(AddRec->getOperand(1))) {

      if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {

        BasicBlock *StrideBB = I->getParent();

        BasicBlock *Preheader = L->getLoopPreheader();

        if (!DT->dominates(StrideBB, Preheader))

          return false;

      }

    }



    DOUT << "[" << L->getHeader()->getName()

         << "] Variable stride: " << *AddRec << "\n";

  }



  Stride = AddRec->getOperand(1);

  return true;
@@ -547,7 +559,7 @@ bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L, 
  // Get the start and stride for this expression.

  SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());

  SCEVHandle Stride = Start;

  if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE))

  if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE, DT))

    return false;  // Non-reducible symbolic expression, bail out.



  std::vector<Instruction *> IUsers;

llvm/test/Transforms/LoopStrengthReduce/pr3571.ll

0 → 100644
+27 −0
Original line number Diff line number Diff line 
; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis

; PR3571



target triple = "i386-mingw32"

define void @_ZNK18qdesigner_internal10TreeWidget12drawBranchesEP8QPainterRK5QRectRK11QModelIndex() nounwind {

entry:

	br label %_ZNK11QModelIndex7isValidEv.exit.i



bb.i:		; preds = %_ZNK11QModelIndex7isValidEv.exit.i

	%indvar.next = add i32 %result.0.i, 1		; <i32> [#uses=1]

	br label %_ZNK11QModelIndex7isValidEv.exit.i



_ZNK11QModelIndex7isValidEv.exit.i:		; preds = %bb.i, %entry

	%result.0.i = phi i32 [ 0, %entry ], [ %indvar.next, %bb.i ]		; <i32> [#uses=2]

	%0 = load i32** null, align 4		; <%struct.QAbstractItemDelegate*> [#uses=0]

	br i1 false, label %_ZN18qdesigner_internalL5levelEP18QAbstractItemModelRK11QModelIndex.exit, label %bb.i



_ZN18qdesigner_internalL5levelEP18QAbstractItemModelRK11QModelIndex.exit:		; preds = %_ZNK11QModelIndex7isValidEv.exit.i

	%1 = call i32 @_ZNK9QTreeView11indentationEv(i32* null) nounwind		; <i32> [#uses=1]

	%2 = mul i32 %1, %result.0.i		; <i32> [#uses=1]

	%3 = add i32 %2, -2		; <i32> [#uses=1]

	%4 = add i32 %3, 0		; <i32> [#uses=1]

	store i32 %4, i32* null, align 8

	unreachable

}



declare i32 @_ZNK9QTreeView11indentationEv(i32*)