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[SCEV] Make sure starting block is marked as visited when recursively collecting loop guards. #120749

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Merged
merged 1 commit into from
Dec 31, 2024
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[SCEV] Make sure starting block is marked as visited when recursively collecting loop guards. #120749

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1 change: 1 addition & 0 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15754,6 +15754,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
// original header.
// TODO: share this logic with isLoopEntryGuardedByCond.
unsigned NumCollectedConditions = 0;
VisitedBlocks.insert(Block);
std::pair<const BasicBlock *, const BasicBlock *> Pair(Pred, Block);
for (; Pair.first;
Pair = SE.getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
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26 changes: 26 additions & 0 deletions ...st/Analysis/ScalarEvolution/backedge-taken-count-guard-info-with-multiple-predecessors.ll
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Expand Up @@ -310,3 +310,29 @@ inner.header:
exit:
ret void
}

; Checks correct traversal for loops without a unique predecessor
; outside the loop.
define void @pr120615() {
; CHECK-LABEL: pr120615
; CHECK-NEXT: Determining loop execution counts for: @pr120615
; CHECK-NEXT: Loop %header: backedge-taken count is i32 0
; CHECK-NEXT: Loop %header: constant max backedge-taken count is i32 0
; CHECK-NEXT: Loop %header: symbolic max backedge-taken count is i32 0
; CHECK-NEXT: Loop %header: Trip multiple is 1
entry:
br label %header

bb:
br label %header

header:
%0 = phi i32 [ %1, %header ], [ 0, %bb ], [ 0, %entry ]
%1 = add i32 %0, 1
%icmp = icmp slt i32 %0, 0
br i1 %icmp, label %header, label %exit

exit:
ret void

}
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