[llvm] r345375 - [SimpleLoopUnswitch] Make all checks before actual non-trivial unswitch
Max Kazantsev via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 26 02:52:58 PDT 2018
Author: mkazantsev
Date: Fri Oct 26 02:52:58 2018
New Revision: 345375
URL: http://llvm.org/viewvc/llvm-project?rev=345375&view=rev
Log:
[SimpleLoopUnswitch] Make all checks before actual non-trivial unswitch
We should be able to make all relevant checks before we actually start the non-trivial
unswitching, so that we could guarantee that once we have started the transform,
it will always succeed.
Reviewed By: chandlerc
Differential Revision: https://reviews.llvm.org/D53747
Modified:
llvm/trunk/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp?rev=345375&r1=345374&r2=345375&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp Fri Oct 26 02:52:58 2018
@@ -1792,10 +1792,10 @@ void visitDomSubTree(DominatorTree &DT,
} while (!DomWorklist.empty());
}
-static bool unswitchNontrivialInvariants(
+static void unswitchNontrivialInvariants(
Loop &L, Instruction &TI, ArrayRef<Value *> Invariants,
- DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC,
- function_ref<void(bool, ArrayRef<Loop *>)> UnswitchCB,
+ SmallVectorImpl<BasicBlock *> &ExitBlocks, DominatorTree &DT, LoopInfo &LI,
+ AssumptionCache &AC, function_ref<void(bool, ArrayRef<Loop *>)> UnswitchCB,
ScalarEvolution *SE) {
auto *ParentBB = TI.getParent();
BranchInst *BI = dyn_cast<BranchInst>(&TI);
@@ -1851,17 +1851,6 @@ static bool unswitchNontrivialInvariants
// whatever reason).
assert(LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!");
- SmallVector<BasicBlock *, 4> ExitBlocks;
- L.getUniqueExitBlocks(ExitBlocks);
-
- // We cannot unswitch if exit blocks contain a cleanuppad instruction as we
- // don't know how to split those exit blocks.
- // FIXME: We should teach SplitBlock to handle this and remove this
- // restriction.
- for (auto *ExitBB : ExitBlocks)
- if (isa<CleanupPadInst>(ExitBB->getFirstNonPHI()))
- return false;
-
// Compute the parent loop now before we start hacking on things.
Loop *ParentL = L.getParentLoop();
@@ -2145,7 +2134,6 @@ static bool unswitchNontrivialInvariants
UnswitchCB(IsStillLoop, SibLoops);
++NumBranches;
- return true;
}
/// Recursively compute the cost of a dominator subtree based on the per-block
@@ -2241,6 +2229,19 @@ unswitchBestCondition(Loop &L, Dominator
if (containsIrreducibleCFG<const BasicBlock *>(RPOT, LI))
return false;
+ SmallVector<BasicBlock *, 4> ExitBlocks;
+ L.getUniqueExitBlocks(ExitBlocks);
+
+ // We cannot unswitch if exit blocks contain a cleanuppad instruction as we
+ // don't know how to split those exit blocks.
+ // FIXME: We should teach SplitBlock to handle this and remove this
+ // restriction.
+ for (auto *ExitBB : ExitBlocks)
+ if (isa<CleanupPadInst>(ExitBB->getFirstNonPHI())) {
+ dbgs() << "Cannot unswitch because of cleanuppad in exit block\n";
+ return false;
+ }
+
LLVM_DEBUG(
dbgs() << "Considering " << UnswitchCandidates.size()
<< " non-trivial loop invariant conditions for unswitching.\n");
@@ -2374,11 +2375,12 @@ unswitchBestCondition(Loop &L, Dominator
return false;
}
- LLVM_DEBUG(dbgs() << " Trying to unswitch non-trivial (cost = "
+ LLVM_DEBUG(dbgs() << " Unswitching non-trivial (cost = "
<< BestUnswitchCost << ") terminator: " << *BestUnswitchTI
<< "\n");
- return unswitchNontrivialInvariants(
- L, *BestUnswitchTI, BestUnswitchInvariants, DT, LI, AC, UnswitchCB, SE);
+ unswitchNontrivialInvariants(L, *BestUnswitchTI, BestUnswitchInvariants,
+ ExitBlocks, DT, LI, AC, UnswitchCB, SE);
+ return true;
}
/// Unswitch control flow predicated on loop invariant conditions.
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