From 8a9fd94cfe2382b91b5e56fc6a867770dd8b3332 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Wed, 14 Apr 2004 21:11:25 +0000 Subject: [PATCH] This is a trivial tweak to the addrec insertion code: insert the increment at the bottom of the loop instead of the top. This reduces the number of overlapping live ranges a lot, for example, eliminating a spill in an important loop in 183.equake with linear scan. I still need to make the exit comparison of the loop use the post-incremented version of this variable, but this is an easy first step. llvm-svn: 12952 --- llvm/lib/Analysis/ScalarEvolution.cpp | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 70a7d04121cc..62247e42ac49 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -1465,14 +1465,19 @@ Value *SCEVAddRecExpr::expandCodeFor(ScalarEvolutionRewriter &SER, PHINode *PN = new PHINode(Ty, "indvar", Header->begin()); PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader()); - // Insert a unit add instruction after the PHI nodes in the header block. - BasicBlock::iterator I = PN; - while (isa(I)) ++I; - - Constant *One = Ty->isFloatingPoint() ?(Constant*)ConstantFP::get(Ty, 1.0) - :(Constant*)ConstantInt::get(Ty, 1); + pred_iterator HPI = pred_begin(Header); + assert(HPI != pred_end(Header) && "Loop with zero preds???"); + if (!getLoop()->contains(*HPI)) ++HPI; + assert(HPI != pred_end(Header) && getLoop()->contains(*HPI) && + "No backedge in loop?"); + + // Insert a unit add instruction right before the terminator corresponding + // to the back-edge. + Constant *One = Ty->isFloatingPoint() ? (Constant*)ConstantFP::get(Ty, 1.0) + : (Constant*)ConstantInt::get(Ty, 1); Instruction *Add = BinaryOperator::create(Instruction::Add, PN, One, - "indvar.next", I); + "indvar.next", + (*HPI)->getTerminator()); pred_iterator PI = pred_begin(Header); if (*PI == L->getLoopPreheader()) -- GitLab