[llvm-branch-commits] [llvm] 3b6481e - Revert "[SCEV] Use isKnownPredicateAt in isLoopBackedgeGuardedByCond"
Max Kazantsev via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Nov 26 01:48:00 PST 2020
Author: Max Kazantsev
Date: 2020-11-26T16:42:43+07:00
New Revision: 3b6481eae2597f656b9f5bb6a5eb5438eb8cb294
URL: https://github.com/llvm/llvm-project/commit/3b6481eae2597f656b9f5bb6a5eb5438eb8cb294
DIFF: https://github.com/llvm/llvm-project/commit/3b6481eae2597f656b9f5bb6a5eb5438eb8cb294.diff
LOG: Revert "[SCEV] Use isKnownPredicateAt in isLoopBackedgeGuardedByCond"
This reverts commit 14f2ad0e3cc54d5eb254b545a469e8ffdb62b119.
Reverting to investigate compile time drop.
Differential Revision: https://reviews.llvm.org/D92152
Added:
Modified:
llvm/lib/Analysis/ScalarEvolution.cpp
llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 31b88c92a889..53fd668be05c 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9911,7 +9911,42 @@ ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
if (isImpliedViaGuard(Latch, Pred, LHS, RHS))
return true;
- return isKnownPredicateAt(Pred, LHS, RHS, Latch->getTerminator());
+ 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;
}
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 c39828923d5f..8a07a49303d2 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
@@ -69,7 +69,7 @@ define void @_Z15IntegerToStringjjR7Vector2(i32 %i, i32 %radix, %struct.Vector2*
; 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 nuw nsw i64 [[LSR_IV]], 2
+; CHECK-NEXT: [[LSR_IV_NEXT]] = add 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]*
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