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llvm-svn: 139375
This commit is contained in:
Andrew Trick 2011-09-09 17:35:10 +00:00
parent 8a2e622f38
commit 77fa88a786
1 changed files with 16 additions and 15 deletions
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31
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -621,12 +621,12 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
// To be replaced by -disable-iv-rewrite.
//===----------------------------------------------------------------------===//
// FIXME: It is an extremely bad idea to indvar substitute anything more
// complex than affine induction variables. Doing so will put expensive
// polynomial evaluations inside of the loop, and the str reduction pass
// currently can only reduce affine polynomials. For now just disable
// indvar subst on anything more complex than an affine addrec, unless
// it can be expanded to a trivial value.
/// FIXME: It is an extremely bad idea to indvar substitute anything more
/// complex than affine induction variables. Doing so will put expensive
/// polynomial evaluations inside of the loop, and the str reduction pass
/// currently can only reduce affine polynomials. For now just disable
/// indvar subst on anything more complex than an affine addrec, unless
/// it can be expanded to a trivial value.
static bool isSafe(const SCEV *S, const Loop *L, ScalarEvolution *SE) {
// Loop-invariant values are safe.
if (SE->isLoopInvariant(S, L)) return true;
@ -637,7 +637,8 @@ static bool isSafe(const SCEV *S, const Loop *L, ScalarEvolution *SE) {
return AR->isAffine();
// An add is safe it all its operands are safe.
if (const SCEVCommutativeExpr *Commutative = dyn_cast<SCEVCommutativeExpr>(S)) {
if (const SCEVCommutativeExpr *Commutative
= dyn_cast<SCEVCommutativeExpr>(S)) {
for (SCEVCommutativeExpr::op_iterator I = Commutative->op_begin(),
E = Commutative->op_end(); I != E; ++I)
if (!isSafe(*I, L, SE)) return false;
@ -950,11 +951,11 @@ static bool HoistStep(Instruction *IncV, Instruction *InsertPos,
return true;
}
// GetWideRecurrence - Is this instruction potentially interesting from IVUsers'
// perspective after widening it's type? In other words, can the extend be
// safely hoisted out of the loop with SCEV reducing the value to a recurrence
// on the same loop. If so, return the sign or zero extended
// recurrence. Otherwise return NULL.
/// GetWideRecurrence - Is this instruction potentially interesting from
/// IVUsers' perspective after widening it's type? In other words, can the
/// extend be safely hoisted out of the loop with SCEV reducing the value to a
/// recurrence on the same loop. If so, return the sign or zero extended
/// recurrence. Otherwise return NULL.
const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
if (!SE->isSCEVable(NarrowUse->getType()))
return 0;
@ -1270,9 +1271,9 @@ void IndVarSimplify::SimplifyCongruentIVs(Loop *L) {
// LinearFunctionTestReplace and its kin. Rewrite the loop exit condition.
//===----------------------------------------------------------------------===//
// Check for expressions that ScalarEvolution generates to compute
// BackedgeTakenInfo. If these expressions have not been reduced, then expanding
// them may incur additional cost (albeit in the loop preheader).
/// Check for expressions that ScalarEvolution generates to compute
/// BackedgeTakenInfo. If these expressions have not been reduced, then
/// expanding them may incur additional cost (albeit in the loop preheader).
static bool isHighCostExpansion(const SCEV *S, BranchInst *BI,
ScalarEvolution *SE) {
// If the backedge-taken count is a UDiv, it's very likely a UDiv that