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Move RemoveRedundantDbgInstrs outside of inner loop in JumpThreading #123008

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Merged
merged 3 commits into from
Jan 22, 2025
Merged

Move RemoveRedundantDbgInstrs outside of inner loop in JumpThreading #123008

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8aecbed
[NFC] Move RemoveRedundantDbgInstrs outside of inner loop in JumpThre…
huangjd Jan 15, 2025
4becdbd
Updated test case, now cleanup redundant dbg value happens once at th…
huangjd Jan 16, 2025
056a3de
address comments in PR
huangjd Jan 21, 2025
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13 changes: 7 additions & 6 deletions llvm/lib/Transforms/Scalar/JumpThreading.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -330,11 +330,6 @@ bool JumpThreadingPass::runImpl(Function &F_, FunctionAnalysisManager *FAM_,
while (processBlock(&BB)) // Thread all of the branches we can over BB.
Changed = ChangedSinceLastAnalysisUpdate = true;

// Jump threading may have introduced redundant debug values into BB
// which should be removed.
if (Changed)
RemoveRedundantDbgInstrs(&BB);

// Stop processing BB if it's the entry or is now deleted. The following
// routines attempt to eliminate BB and locating a suitable replacement
// for the entry is non-trivial.
Expand Down Expand Up @@ -366,7 +361,6 @@ bool JumpThreadingPass::runImpl(Function &F_, FunctionAnalysisManager *FAM_,
// detect and transform nested loops later.
!LoopHeaders.count(&BB) && !LoopHeaders.count(Succ) &&
TryToSimplifyUncondBranchFromEmptyBlock(&BB, DTU.get())) {
RemoveRedundantDbgInstrs(Succ);
// BB is valid for cleanup here because we passed in DTU. F remains
// BB's parent until a DTU->getDomTree() event.
LVI->eraseBlock(&BB);
Expand All @@ -377,6 +371,13 @@ bool JumpThreadingPass::runImpl(Function &F_, FunctionAnalysisManager *FAM_,
EverChanged |= Changed;
} while (Changed);

// Jump threading may have introduced redundant debug values into BB which
// should be removed.
if (EverChanged)
for (auto &BB : *F) {
RemoveRedundantDbgInstrs(&BB);
}

LoopHeaders.clear();
return EverChanged;
}
Expand Down
5 changes: 0 additions & 5 deletions llvm/test/Transforms/JumpThreading/thread-debug-info.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -92,10 +92,6 @@ exit: ; preds = %bb.f4, %bb.f3, %bb.
ret void, !dbg !29
}

; Test for the cloning of dbg.values on elided instructions -- down one path
; being threaded, the `and` in the function below is optimised away, but its
; debug-info should still be preserved.
; Similarly, the call to f1 gets cloned, its dbg.value should be cloned too.
define void @test16(i1 %c, i1 %c2, i1 %c3, i1 %c4) nounwind ssp !dbg !30 {
; CHECK-LABEL: define void @test16(i1
entry:
Expand All @@ -109,7 +105,6 @@ lor.lhs.false.i:
br i1 %c3, label %land.end, label %land.end, !dbg !33

; CHECK-LABEL: land.end.thr_comm:
; CHECK-NEXT: #dbg_value(i32 0,
; CHECK-NEXT: #dbg_value(i32 1,
; CHECK-NEXT: call void @f1()
; CHECK-NEXT: br i1 %c4,
Expand Down
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