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Fix flipped sign. While there, show my math.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139135 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-09-06 05:33:18 +00:00
parent 980e9f399d
commit 28682ae00f
1 changed files with 9 additions and 2 deletions
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11
lib/Analysis/ScalarEvolution.cpp
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@ -1976,7 +1976,13 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
++OtherIdx)
if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
// {A,+,B}<L> * {C,+,D}<L> --> {A*C,+,A*D + B*C + B*D,+,2*B*D}<L>
// {A,+,B}<L> * {C,+,D}<L> --> {A*C,+,A*D + B*C - B*D,+,2*B*D}<L>
//
// For reference, given that {X,+,Y,+,Z} = x + y*It + z*It^2 then
// X = x, Y = y-z, Z = 2z.
//
// x = A*C, y = (A*D + B*C), z = B*D
// Therefore X = A*C, Y = (A*D + B*C) - B*D and Z = 2*B*D.
for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
++OtherIdx)
if (const SCEVAddRecExpr *OtherAddRec =
@ -1989,7 +1995,8 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
const SCEV *NewStart = getMulExpr(A, C);
const SCEV *BD = getMulExpr(B, D);
const SCEV *NewStep = getAddExpr(getMulExpr(A, D),
getMulExpr(B, C), BD);
getMulExpr(B, C),
getNegativeSCEV(BD));
const SCEV *NewSecondOrderStep =
getMulExpr(BD, getConstant(BD->getType(), 2));