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[VectorCombine] Shrink loads used in shufflevector rebroadcasts #128938

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Merged
merged 23 commits into from
Aug 4, 2025
Merged

[VectorCombine] Shrink loads used in shufflevector rebroadcasts #128938

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1d817c3
[AggressiveInstCombine] Shrink loads used in shufflevector rebroadcasts.
Feb 26, 2025
09ac59a
Add implementation and update tests.
Feb 26, 2025
bc8e5ce
Fix broken tests.
Feb 28, 2025
6f6fc11
Ignore non-simple loads.
Mar 4, 2025
7499a48
Move transform to VectorCombine and update tests.
Mar 12, 2025
c86d296
Address review comments and update tests.
Mar 14, 2025
16f7320
Code formatting.
Mar 14, 2025
dfe3459
Add cost analysis for shufflevector ops and update tests.
Mar 21, 2025
125c3f2
Code formatting.
Mar 21, 2025
3afabd1
Address comments.
Mar 24, 2025
875c408
Fix conflict with subvector load widening.
Mar 26, 2025
839f7bd
Fix build bot false positive for undef.
Mar 26, 2025
9518894
Address comments.
May 7, 2025
016e9a5
Address review comments.
May 19, 2025
76450c9
Address comments.
May 30, 2025
dcccc92
Formatting.
May 30, 2025
fa2ebe8
Correct renaming and remove function-style casts.
May 30, 2025
863f10f
Remove auto.
Jun 11, 2025
5f122f6
Fix cost analysis after rebase.
Jul 8, 2025
0373b90
Add debug message.
Jul 9, 2025
204d4bf
Address comments.
Jul 16, 2025
bceb357
Remove redundant code and update tests.
Jul 16, 2025
6af4449
Merge branch 'main' into shrink_loads
RKSimon Aug 4, 2025
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Address comments.
  • Loading branch information
Leon Clark committed Jul 8, 2025
commit 9518894f07bdd98dd2a34946871d75d84a224c9a
16 changes: 6 additions & 10 deletions llvm/lib/Transforms/Vectorize/VectorCombine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3713,23 +3713,19 @@ bool VectorCombine::shrinkLoadForShuffles(Instruction &I) {
auto GetIndexRangeInShuffles = [&]() -> std::optional<IndexRange> {
IndexRange OutputRange = IndexRange(VecTy->getNumElements(), -1);
for (auto &Use : I.uses()) {
// All uses must be shufflevector instructions.
auto *Shuffle = dyn_cast<ShuffleVectorInst>(Use.getUser());
if (!Shuffle)
// Ensure all uses match the required pattern.
User *Shuffle = Use.getUser();
Value *Op0 = nullptr;
ArrayRef<int> Mask;

if (!match(Shuffle, m_Shuffle(m_Value(Op0), m_Undef(), m_Mask(Mask))))
return std::nullopt;

// Ignore shufflevector instructions that have no uses.
if (!Shuffle->hasNUsesOrMore(1u))
continue;

// Ensure second operand is a poison value.
auto *Op0 = Shuffle->getOperand(0);
auto *Op1 = Shuffle->getOperand(1);
if (!isa<PoisonValue>(Op1) && !isa<UndefValue>(Op1))
return std::nullopt;

// Find the min and max indices used by the shufflevector instruction.
ArrayRef<int> Mask = Shuffle->getShuffleMask();
auto *Op0Ty = cast<FixedVectorType>(Op0->getType());
auto NumElems = int(Op0Ty->getNumElements());

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