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14 changes: 6 additions & 8 deletions llvm/lib/Transforms/Scalar/Sink.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -82,11 +82,6 @@ static bool IsAcceptableTarget(Instruction *Inst, BasicBlock *SuccToSinkTo,
!Inst->hasMetadata(LLVMContext::MD_invariant_load))
return false;

// We don't want to sink across a critical edge if we don't dominate the
// successor. We could be introducing calculations to new code paths.
if (!DT.dominates(Inst->getParent(), SuccToSinkTo))
return false;

// Don't sink instructions into a loop.
Loop *succ = LI.getLoopFor(SuccToSinkTo);
Loop *cur = LI.getLoopFor(Inst->getParent());
Expand Down Expand Up @@ -144,9 +139,6 @@ static bool SinkInstruction(Instruction *Inst,
SuccToSinkTo = DT.findNearestCommonDominator(SuccToSinkTo, UseBlock);
else
SuccToSinkTo = UseBlock;
// The current basic block needs to dominate the candidate.
if (!DT.dominates(BB, SuccToSinkTo))
return false;
}

if (SuccToSinkTo) {
Expand All @@ -167,6 +159,12 @@ static bool SinkInstruction(Instruction *Inst,
Inst->getParent()->printAsOperand(dbgs(), false); dbgs() << " -> ";
SuccToSinkTo->printAsOperand(dbgs(), false); dbgs() << ")\n");

// The current location of Inst dominates all uses, thus it must dominate
// SuccToSinkTo, which is on the IDom chain between the nearest common
// dominator to all uses and the current location.
assert(DT.dominates(BB, SuccToSinkTo) &&
"SuccToSinkTo must be dominated by current Inst location!");

// Move the instruction.
Inst->moveBefore(SuccToSinkTo->getFirstInsertionPt());
return true;
Expand Down
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