[llvm-commits] [llvm] r139135 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp
Nick Lewycky
nicholas at mxc.ca
Mon Sep 5 22:33:18 PDT 2011
Author: nicholas
Date: Tue Sep 6 00:33:18 2011
New Revision: 139135
URL: http://llvm.org/viewvc/llvm-project?rev=139135&view=rev
Log:
Fix flipped sign. While there, show my math.
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=139135&r1=139134&r2=139135&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Sep 6 00:33:18 2011
@@ -1976,7 +1976,13 @@
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 *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));
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