6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-15 05:24:01 +00:00
Code Issues Projects Releases Wiki Activity

Simplify this code. LoopDeletion doesn't need to explicit check that

Browse Source 
the loop exiting block dominates the latch block; if ScalarEvolution
can prove that the trip-count is finite, that's sufficient.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85165 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-10-26 22:18:58 +00:00
parent fe3595555a
commit 06d4033a35
1 changed files with 2 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
lib/Transforms/Scalar/LoopDeletion.cpp
View File

@ -33,8 +33,6 @@ namespace {
// Possibly eliminate loop L if it is dead. // Possibly eliminate loop L if it is dead.
bool runOnLoop(Loop* L, LPPassManager& LPM); bool runOnLoop(Loop* L, LPPassManager& LPM);
bool SingleDominatingExit(Loop* L,
SmallVector<BasicBlock*, 4>& exitingBlocks);
bool IsLoopDead(Loop* L, SmallVector<BasicBlock*, 4>& exitingBlocks, bool IsLoopDead(Loop* L, SmallVector<BasicBlock*, 4>& exitingBlocks,
SmallVector<BasicBlock*, 4>& exitBlocks, SmallVector<BasicBlock*, 4>& exitBlocks,
bool &Changed, BasicBlock *Preheader); bool &Changed, BasicBlock *Preheader);
@ -63,25 +61,6 @@ Pass* llvm::createLoopDeletionPass() {
return new LoopDeletion(); return new LoopDeletion();
} }
/// SingleDominatingExit - Checks that there is only a single blocks that
/// branches out of the loop, and that it also g the latch block. Loops
/// with multiple or non-latch-dominating exiting blocks could be dead, but we'd
/// have to do more extensive analysis to make sure, for instance, that the
/// control flow logic involved was or could be made loop-invariant.
bool LoopDeletion::SingleDominatingExit(Loop* L,
SmallVector<BasicBlock*, 4>& exitingBlocks) {
if (exitingBlocks.size() != 1)
return false;
BasicBlock* latch = L->getLoopLatch();
if (!latch)
return false;
DominatorTree& DT = getAnalysis<DominatorTree>();
return DT.dominates(exitingBlocks[0], latch);
}
/// IsLoopDead - Determined if a loop is dead. This assumes that we've already /// IsLoopDead - Determined if a loop is dead. This assumes that we've already
/// checked for unique exit and exiting blocks, and that the code is in LCSSA /// checked for unique exit and exiting blocks, and that the code is in LCSSA
/// form. /// form.
@ -154,9 +133,8 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
if (exitBlocks.size() != 1) if (exitBlocks.size() != 1)
return false; return false;
// Loops with multiple exits or exits that don't dominate the latch // Loops with multiple exits are too complicated to handle correctly.
// are too complicated to handle correctly. if (exitingBlocks.size() != 1)
if (!SingleDominatingExit(L, exitingBlocks))
return false; return false;
// Finally, we have to check that the loop really is dead. // Finally, we have to check that the loop really is dead.