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indvars: sink truncates outside the loop.

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This is a follow up of the r198338 commit that added truncates for
lcssa phi nodes. Sinking the truncates below the phis cleans up the
loop and simplifies subsequent analysis within the indvars pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198654 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2014-01-07 01:02:55 +00:00
parent f86063e7ec
commit ced88c5918
2 changed files with 27 additions and 7 deletions
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27
lib/Transforms/Scalar/IndVarSimplify.cpp
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@@ -883,6 +883,8 @@ const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
/// This IV user cannot be widen. Replace this use of the original narrow IV
/// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT) {
DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef
<< " for user " << *DU.NarrowUse << "\n");
IRBuilder<> Builder(getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT));
Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
@@ -893,10 +895,27 @@ static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT) {
Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
// Stop traversing the def-use chain at inner-loop phis or post-loop phis.
if (isa<PHINode>(DU.NarrowUse) &&
LI->getLoopFor(DU.NarrowUse->getParent()) != L) {
truncateIVUse(DU, DT);
return 0;
if (PHINode *UsePhi = dyn_cast<PHINode>(DU.NarrowUse)) {
if (LI->getLoopFor(UsePhi->getParent()) != L) {
// For LCSSA phis, sink the truncate outside the loop.
// After SimplifyCFG most loop exit targets have a single predecessor.
// Otherwise fall back to a truncate within the loop.
if (UsePhi->getNumOperands() != 1)
truncateIVUse(DU, DT);
else {
PHINode *WidePhi =
PHINode::Create(DU.WideDef->getType(), 1, UsePhi->getName() + ".wide",
UsePhi);
WidePhi->addIncoming(DU.WideDef, UsePhi->getIncomingBlock(0));
IRBuilder<> Builder(WidePhi->getParent()->getFirstInsertionPt());
Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType());
UsePhi->replaceAllUsesWith(Trunc);
DeadInsts.push_back(UsePhi);
DEBUG(dbgs() << "INDVARS: Widen lcssa phi " << *UsePhi
<< " to " << *WidePhi << "\n");
}
return 0;
}
}
// Our raison d'etre! Eliminate sign and zero extension.
if (IsSigned ? isa<SExtInst>(DU.NarrowUse) : isa<ZExtInst>(DU.NarrowUse)) {