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-rw-r--r--llvm/lib/Transforms/Utils/LoopUnroll.cpp46
-rw-r--r--llvm/test/Transforms/LoopUnroll/invalidate_right_loop.ll51
2 files changed, 69 insertions, 28 deletions
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 9fb7d68e5fd..e18bf947123 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -97,15 +97,9 @@ static inline void remapInstruction(Instruction *I,
/// Folds a basic block into its predecessor if it only has one predecessor, and
/// that predecessor only has one successor.
-/// The LoopInfo Analysis that is passed will be kept consistent. If folding is
-/// successful references to the containing loop must be removed from
-/// ScalarEvolution by calling ScalarEvolution::forgetLoop because SE may have
-/// references to the eliminated BB. The argument ForgottenLoops contains a set
-/// of loops that have already been forgotten to prevent redundant, expensive
-/// calls to ScalarEvolution::forgetLoop. Returns the new combined block.
+/// The LoopInfo Analysis that is passed will be kept consistent.
static BasicBlock *
foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI, ScalarEvolution *SE,
- SmallPtrSetImpl<Loop *> &ForgottenLoops,
DominatorTree *DT) {
// Merge basic blocks into their predecessor if there is only one distinct
// pred, and if there is only one distinct successor of the predecessor, and
@@ -149,13 +143,6 @@ foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI, ScalarEvolution *SE,
DT->eraseNode(BB);
}
- // ScalarEvolution holds references to loop exit blocks.
- if (SE) {
- if (Loop *L = LI->getLoopFor(BB)) {
- if (ForgottenLoops.insert(L).second)
- SE->forgetLoop(L);
- }
- }
LI->removeBlock(BB);
// Inherit predecessor's name if it exists...
@@ -450,11 +437,6 @@ LoopUnrollResult llvm::UnrollLoop(
}
}
- // Notify ScalarEvolution that the loop will be substantially changed,
- // if not outright eliminated.
- if (SE)
- SE->forgetLoop(L);
-
// If we know the trip count, we know the multiple...
unsigned BreakoutTrip = 0;
if (TripCount != 0) {
@@ -521,6 +503,21 @@ LoopUnrollResult llvm::UnrollLoop(
DEBUG(dbgs() << "!\n");
}
+ // We are going to make changes to this loop. SCEV may be keeping cached info
+ // about it, in particular about backedge taken count. The changes we make
+ // are guaranteed to invalidate this information for our loop. It is tempting
+ // to only invalidate the loop being unrolled, but it is incorrect as long as
+ // all exiting branches from all inner loops have impact on the outer loops,
+ // and if something changes inside them then any of outer loops may also
+ // change. When we forget outermost loop, we also forget all contained loops
+ // and this is what we need here.
+ if (SE) {
+ const Loop *CurrL = L;
+ while (const Loop *ParentL = CurrL->getParentLoop())
+ CurrL = ParentL;
+ SE->forgetLoop(CurrL);
+ }
+
bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
BasicBlock *LoopExit = BI->getSuccessor(ContinueOnTrue);
@@ -578,14 +575,9 @@ LoopUnrollResult llvm::UnrollLoop(
"Header should not be in a sub-loop");
// Tell LI about New.
const Loop *OldLoop = addClonedBlockToLoopInfo(*BB, New, LI, NewLoops);
- if (OldLoop) {
+ if (OldLoop)
LoopsToSimplify.insert(NewLoops[OldLoop]);
- // Forget the old loop, since its inputs may have changed.
- if (SE)
- SE->forgetLoop(OldLoop);
- }
-
if (*BB == Header)
// Loop over all of the PHI nodes in the block, changing them to use
// the incoming values from the previous block.
@@ -774,13 +766,11 @@ LoopUnrollResult llvm::UnrollLoop(
DT->verify(DominatorTree::VerificationLevel::Fast));
// Merge adjacent basic blocks, if possible.
- SmallPtrSet<Loop *, 4> ForgottenLoops;
for (BasicBlock *Latch : Latches) {
BranchInst *Term = cast<BranchInst>(Latch->getTerminator());
if (Term->isUnconditional()) {
BasicBlock *Dest = Term->getSuccessor(0);
- if (BasicBlock *Fold =
- foldBlockIntoPredecessor(Dest, LI, SE, ForgottenLoops, DT)) {
+ if (BasicBlock *Fold = foldBlockIntoPredecessor(Dest, LI, SE, DT)) {
// Dest has been folded into Fold. Update our worklists accordingly.
std::replace(Latches.begin(), Latches.end(), Dest, Fold);
UnrolledLoopBlocks.erase(std::remove(UnrolledLoopBlocks.begin(),
diff --git a/llvm/test/Transforms/LoopUnroll/invalidate_right_loop.ll b/llvm/test/Transforms/LoopUnroll/invalidate_right_loop.ll
new file mode 100644
index 00000000000..cb769af63c7
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/invalidate_right_loop.ll
@@ -0,0 +1,51 @@
+; RUN: opt < %s -S -indvars -loop-unroll -verify-dom-info | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Make sure that this test doesn't crash because of dangling pointer in SCEV.
+declare void @llvm.experimental.guard(i1, ...)
+
+define void @test(i32* %p, i8** %p2, i64* %dest) {
+
+; CHECK-LABEL: @test(
+
+entry:
+ br label %outer.loop
+
+outer.loop: ; preds = %outer.latch, %entry
+ %local_2_ = phi i32 [ 10, %entry ], [ %tmp2, %outer.latch ]
+ %tmp1 = icmp eq i32 %local_2_, 0
+ br label %inner.loop
+
+outer.latch: ; preds = %inner.latch
+ %tmp2 = add i32 %local_2_, 1
+ br label %outer.loop
+
+inner.loop: ; preds = %inner.latch, %outer.loop
+ %local_4_20 = phi i32 [ 7, %outer.loop ], [ %tmp15, %inner.latch ]
+ %tmp6 = icmp eq i32 %local_4_20, 0
+ call void (i1, ...) @llvm.experimental.guard(i1 %tmp6) [ "deopt"() ]
+ br label %innermost.loop
+
+store.block: ; preds = %innermost.loop
+ store i64 %tmp20, i64* %dest, align 8
+ br i1 %tmp1, label %exit, label %inner.latch
+
+inner.latch: ; preds = %store.block
+ %tmp15 = add i32 %local_4_20, 4
+ %tmp16 = icmp sgt i32 %tmp15, 263
+ br i1 %tmp16, label %outer.latch, label %inner.loop
+
+innermost.loop: ; preds = %innermost.loop, %inner.loop
+ %tmp17 = phi i64 [ 0, %inner.loop ], [ %tmp20, %innermost.loop ]
+ %local_6_51 = phi i32 [ 1, %inner.loop ], [ %tmp21, %innermost.loop ]
+ %ze = zext i32 %local_6_51 to i64
+ %tmp20 = add i64 %tmp17, %ze
+ %tmp21 = add nuw nsw i32 %local_6_51, 1
+ %tmp22 = icmp ugt i32 %local_6_51, 5
+ br i1 %tmp22, label %store.block, label %innermost.loop
+
+exit: ; preds = %store.block
+ ret void
+}
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