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Move trip count discovery outside of the generic LoopUnroll helper. This 

removes its dependence on canonical induction variables.

llvm-svn: 135829
This commit is contained in:
Andrew Trick 2011-07-23 00:33:05 +00:00
parent 279e7a6c83
commit 1cabe54fab
3 changed files with 11 additions and 15 deletions
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3
llvm/include/llvm/Transforms/Utils/UnrollLoop.h
View File

@ -22,7 +22,8 @@ class Loop;
class LoopInfo;
class LPPassManager;
bool UnrollLoop(Loop *L, unsigned Count, LoopInfo* LI, LPPassManager* LPM);
bool UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
unsigned TripMultiple, LoopInfo* LI, LPPassManager* LPM);
}

9
llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -137,9 +137,14 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
// Find trip count
unsigned TripCount = L->getSmallConstantTripCount();
unsigned Count = CurrentCount;
// Find trip multiple if count is not available
unsigned TripMultiple = 1;
if (TripCount == 0)
TripMultiple = L->getSmallConstantTripMultiple();
// Automatically select an unroll count.
unsigned Count = CurrentCount;
if (Count == 0) {
// Conservative heuristic: if we know the trip count, see if we can
// completely unroll (subject to the threshold, checked below); otherwise
@ -183,7 +188,7 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
// Unroll the loop.
Function *F = L->getHeader()->getParent();
if (!UnrollLoop(L, Count, LI, &LPM))
if (!UnrollLoop(L, Count, TripCount, TripMultiple, LI, &LPM))
return false;
// FIXME: Reconstruct dom info, because it is not preserved properly.

14
llvm/lib/Transforms/Utils/LoopUnroll.cpp
View File

@ -11,9 +11,6 @@
// actual pass or policy, but provides a single function to perform loop
// unrolling.
//
// It works best when loops have been canonicalized by the -indvars pass,
// allowing it to determine the trip counts of loops easily.
//
// The process of unrolling can produce extraneous basic blocks linked with
// unconditional branches. This will be corrected in the future.
//
@ -113,8 +110,8 @@ static BasicBlock *FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI) {
///
/// If a LoopPassManager is passed in, and the loop is fully removed, it will be
/// removed from the LoopPassManager as well. LPM can also be NULL.
bool llvm::UnrollLoop(Loop *L, unsigned Count,
LoopInfo *LI, LPPassManager *LPM) {
bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
unsigned TripMultiple, LoopInfo *LI, LPPassManager *LPM) {
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
DEBUG(dbgs() << " Can't unroll; loop preheader-insertion failed.\n");
@ -149,13 +146,6 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count,
if (ScalarEvolution *SE = LPM->getAnalysisIfAvailable<ScalarEvolution>())
SE->forgetLoop(L);
// Find trip count
unsigned TripCount = L->getSmallConstantTripCount();
// Find trip multiple if count is not available
unsigned TripMultiple = 1;
if (TripCount == 0)
TripMultiple = L->getSmallConstantTripMultiple();
if (TripCount != 0)
DEBUG(dbgs() << " Trip Count = " << TripCount << "\n");
if (TripMultiple != 1)