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This is a trivial tweak to the addrec insertion code: insert the increment

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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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12952 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-04-14 21:11:25 +00:00
parent 50872d5385
commit 16011e6201
1 changed files with 11 additions and 6 deletions
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17
lib/Analysis/ScalarEvolution.cpp
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@ -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<PHINode>(I)) ++I;
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?");
Constant *One = Ty->isFloatingPoint() ?(Constant*)ConstantFP::get(Ty, 1.0)
:(Constant*)ConstantInt::get(Ty, 1);
// 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())