From f63ae2159d2c20ea239e4c6d4e74bd2f14ebd408 Mon Sep 17 00:00:00 2001 From: Andrew Trick Date: Wed, 28 Sep 2011 17:02:54 +0000 Subject: [PATCH] indvars: generalize SCEV getPreStartForSignExtend. Handle general Add expressions to avoid leaving around redundant 32-bit IVs. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140701 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index b1662a02608..ea45e9d72c7 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -1070,14 +1070,26 @@ static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR, // Check for a simple looking step prior to loop entry. const SCEVAddExpr *SA = dyn_cast(Start); - if (!SA || SA->getNumOperands() != 2 || SA->getOperand(0) != Step) + if (!SA) + return 0; + + // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV + // subtraction is expensive. For this purpose, perform a quick and dirty + // difference, by checking for Step in the operand list. + SmallVector DiffOps; + for (SCEVAddExpr::op_iterator I = SA->op_begin(), E = SA->op_end(); + I != E; ++I) { + if (*I != Step) + DiffOps.push_back(*I); + } + if (DiffOps.size() == SA->getNumOperands()) return 0; // This is a postinc AR. Check for overflow on the preinc recurrence using the // same three conditions that getSignExtendedExpr checks. // 1. NSW flags on the step increment. - const SCEV *PreStart = SA->getOperand(1); + const SCEV *PreStart = SE->getAddExpr(DiffOps, SA->getNoWrapFlags()); const SCEVAddRecExpr *PreAR = dyn_cast( SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));