[SCEV] Use isBasicBlockEntryGuardedByCond in isLoopBackedgeGuardedByCond
Previously we tried to using isKnownPredicateAt, but it makes an
extra query to isKnownPredicate, which has negative impact on compile
time. Let's try to use more lightweight isBasicBlockEntryGuardedByCond.
Differential Revision: https://reviews.llvm.org/D92152
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 53fd668..b7bd54a 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9911,42 +9911,7 @@
if (isImpliedViaGuard(Latch, Pred, LHS, RHS))
return true;
- for (DomTreeNode *DTN = DT[Latch], *HeaderDTN = DT[L->getHeader()];
- DTN != HeaderDTN; DTN = DTN->getIDom()) {
- assert(DTN && "should reach the loop header before reaching the root!");
-
- BasicBlock *BB = DTN->getBlock();
- if (isImpliedViaGuard(BB, Pred, LHS, RHS))
- return true;
-
- BasicBlock *PBB = BB->getSinglePredecessor();
- if (!PBB)
- continue;
-
- BranchInst *ContinuePredicate = dyn_cast<BranchInst>(PBB->getTerminator());
- if (!ContinuePredicate || !ContinuePredicate->isConditional())
- continue;
-
- Value *Condition = ContinuePredicate->getCondition();
-
- // If we have an edge `E` within the loop body that dominates the only
- // latch, the condition guarding `E` also guards the backedge. This
- // reasoning works only for loops with a single latch.
-
- BasicBlockEdge DominatingEdge(PBB, BB);
- if (DominatingEdge.isSingleEdge()) {
- // We're constructively (and conservatively) enumerating edges within the
- // loop body that dominate the latch. The dominator tree better agree
- // with us on this:
- assert(DT.dominates(DominatingEdge, Latch) && "should be!");
-
- if (isImpliedCond(Pred, LHS, RHS, Condition,
- BB != ContinuePredicate->getSuccessor(0)))
- return true;
- }
- }
-
- return false;
+ return isBasicBlockEntryGuardedByCond(Latch, Pred, LHS, RHS);
}
bool ScalarEvolution::isBasicBlockEntryGuardedByCond(const BasicBlock *BB,
diff --git a/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll b/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
index 8a07a49..c398289 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
@@ -69,7 +69,7 @@
; CHECK-NEXT: [[UGLYGEP2:%.*]] = bitcast i8* [[UGLYGEP]] to i16*
; CHECK-NEXT: [[TMP29:%.*]] = load i16, i16* [[LSR_IV810]], align 2
; CHECK-NEXT: store i16 [[TMP29]], i16* [[UGLYGEP2]], align 2
-; CHECK-NEXT: [[LSR_IV_NEXT]] = add i64 [[LSR_IV]], 2
+; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i64 [[LSR_IV]], 2
; CHECK-NEXT: [[LSR_IV_NEXT3:%.*]] = inttoptr i64 [[LSR_IV_NEXT]] to i16*
; CHECK-NEXT: [[SCEVGEP9:%.*]] = getelementptr [33 x i16], [33 x i16]* [[LSR_IV8]], i64 0, i64 1
; CHECK-NEXT: [[TMP3]] = bitcast i16* [[SCEVGEP9]] to [33 x i16]*
