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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.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64579 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2009-02-15 06:06:15 +00:00
parent f8546f10c2
commit 8f40afe62d
2 changed files with 42 additions and 5 deletions
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20
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -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
@ -437,11 +437,21 @@ static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
Start = SE->getAddExpr(Start, AddRec->getOperand(0));
#ifndef NDEBUG
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";
#endif
}
Stride = AddRec->getOperand(1);
return true;
@ -549,7 +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;

27
test/Transforms/LoopStrengthReduce/pr3571.ll Normal file
View File

@ -0,0 +1,27 @@
; 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*)