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MLIR][Vector] Improve warp distribution robustness #161647

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59 changes: 20 additions & 39 deletions mlir/lib/Dialect/Vector/Transforms/VectorDistribute.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -934,11 +934,13 @@ struct WarpOpDeadResult : public WarpDistributionPattern {
// 3. skipping from the new result types / new yielded values any result
// that has no use or whose yielded value has already been seen.
for (OpResult result : warpOp.getResults()) {
if (result.use_empty())
continue;
Value yieldOperand = yield.getOperand(result.getResultNumber());
auto it = dedupYieldOperandPositionMap.insert(
std::make_pair(yieldOperand, newResultTypes.size()));
dedupResultPositionMap.insert(std::make_pair(result, it.first->second));
if (result.use_empty() || !it.second)
if (!it.second)
continue;
newResultTypes.push_back(result.getType());
newYieldValues.push_back(yieldOperand);
Expand Down Expand Up @@ -1843,16 +1845,16 @@ struct WarpOpScfIfOp : public WarpDistributionPattern {
newWarpOpDistTypes.append(escapingValueDistTypesElse.begin(),
escapingValueDistTypesElse.end());

llvm::SmallDenseMap<unsigned, unsigned> origToNewYieldIdx;
for (auto [idx, val] :
llvm::zip_equal(nonIfYieldIndices, nonIfYieldValues)) {
origToNewYieldIdx[idx] = newWarpOpYieldValues.size();
newWarpOpYieldValues.push_back(val);
newWarpOpDistTypes.push_back(warpOp.getResult(idx).getType());
}
// Create the new `WarpOp` with the updated yield values and types.
WarpExecuteOnLane0Op newWarpOp = moveRegionToNewWarpOpAndReplaceReturns(
rewriter, warpOp, newWarpOpYieldValues, newWarpOpDistTypes);
// Replace the old `WarpOp` with the new one that has additional yield
// values and types.
SmallVector<size_t> newIndices;
WarpExecuteOnLane0Op newWarpOp = moveRegionToNewWarpOpAndAppendReturns(
rewriter, warpOp, newWarpOpYieldValues, newWarpOpDistTypes, newIndices);
// `ifOp` returns the result of the inner warp op.
SmallVector<Type> newIfOpDistResTypes;
for (auto [i, res] : llvm::enumerate(ifOp.getResults())) {
Expand All @@ -1870,8 +1872,8 @@ struct WarpOpScfIfOp : public WarpDistributionPattern {
OpBuilder::InsertionGuard g(rewriter);
rewriter.setInsertionPointAfter(newWarpOp);
auto newIfOp = scf::IfOp::create(
rewriter, ifOp.getLoc(), newIfOpDistResTypes, newWarpOp.getResult(0),
static_cast<bool>(ifOp.thenBlock()),
rewriter, ifOp.getLoc(), newIfOpDistResTypes,
newWarpOp.getResult(newIndices[0]), static_cast<bool>(ifOp.thenBlock()),
static_cast<bool>(ifOp.elseBlock()));
auto encloseRegionInWarpOp =
[&](Block *oldIfBranch, Block *newIfBranch,
Expand All @@ -1888,7 +1890,7 @@ struct WarpOpScfIfOp : public WarpDistributionPattern {
for (size_t i = 0; i < escapingValues.size();
++i, ++warpResRangeStart) {
innerWarpInputVals.push_back(
newWarpOp.getResult(warpResRangeStart));
newWarpOp.getResult(newIndices[warpResRangeStart]));
escapeValToBlockArgIndex[escapingValues[i]] =
innerWarpInputTypes.size();
innerWarpInputTypes.push_back(escapingValueInputTypes[i]);
Expand Down Expand Up @@ -1936,17 +1938,8 @@ struct WarpOpScfIfOp : public WarpDistributionPattern {
// Update the users of `<- WarpOp.yield <- IfOp.yield` to use the new `IfOp`
// result.
for (auto [origIdx, newIdx] : ifResultMapping)
rewriter.replaceAllUsesExcept(warpOp.getResult(origIdx),
rewriter.replaceAllUsesExcept(newWarpOp.getResult(origIdx),
newIfOp.getResult(newIdx), newIfOp);
// Similarly, update any users of the `WarpOp` results that were not
// results of the `IfOp`.
for (auto [origIdx, newIdx] : origToNewYieldIdx)
rewriter.replaceAllUsesWith(warpOp.getResult(origIdx),
newWarpOp.getResult(newIdx));
// Remove the original `WarpOp` and `IfOp`, they should not have any uses
// at this point.
rewriter.eraseOp(ifOp);
rewriter.eraseOp(warpOp);
return success();
}

Expand Down Expand Up @@ -2065,19 +2058,16 @@ struct WarpOpScfForOp : public WarpDistributionPattern {
escapingValueDistTypes.begin(),
escapingValueDistTypes.end());
// Next, we insert all non-`ForOp` yielded values and their distributed
// types. We also create a mapping between the non-`ForOp` yielded value
// index and the corresponding new `WarpOp` yield value index (needed to
// update users later).
llvm::SmallDenseMap<unsigned, unsigned> nonForResultMapping;
// types.
for (auto [i, v] :
llvm::zip_equal(nonForResultIndices, nonForYieldedValues)) {
nonForResultMapping[i] = newWarpOpYieldValues.size();
newWarpOpYieldValues.push_back(v);
newWarpOpDistTypes.push_back(warpOp.getResult(i).getType());
}
// Create the new `WarpOp` with the updated yield values and types.
WarpExecuteOnLane0Op newWarpOp = moveRegionToNewWarpOpAndReplaceReturns(
rewriter, warpOp, newWarpOpYieldValues, newWarpOpDistTypes);
SmallVector<size_t> newIndices;
WarpExecuteOnLane0Op newWarpOp = moveRegionToNewWarpOpAndAppendReturns(
rewriter, warpOp, newWarpOpYieldValues, newWarpOpDistTypes, newIndices);

// Next, we create a new `ForOp` with the init args yielded by the new
// `WarpOp`.
Expand All @@ -2086,7 +2076,7 @@ struct WarpOpScfForOp : public WarpDistributionPattern {
// escaping values in the new `WarpOp`.
SmallVector<Value> newForOpOperands;
for (size_t i = 0; i < escapingValuesStartIdx; ++i)
newForOpOperands.push_back(newWarpOp.getResult(i));
newForOpOperands.push_back(newWarpOp.getResult(newIndices[i]));

// Create a new `ForOp` outside the new `WarpOp` region.
OpBuilder::InsertionGuard g(rewriter);
Expand All @@ -2110,7 +2100,7 @@ struct WarpOpScfForOp : public WarpDistributionPattern {
llvm::SmallDenseMap<Value, int64_t> argIndexMapping;
for (size_t i = escapingValuesStartIdx;
i < escapingValuesStartIdx + escapingValues.size(); ++i) {
innerWarpInput.push_back(newWarpOp.getResult(i));
innerWarpInput.push_back(newWarpOp.getResult(newIndices[i]));
argIndexMapping[escapingValues[i - escapingValuesStartIdx]] =
innerWarpInputType.size();
innerWarpInputType.push_back(
Expand Down Expand Up @@ -2146,20 +2136,11 @@ struct WarpOpScfForOp : public WarpDistributionPattern {
if (!innerWarp.getResults().empty())
scf::YieldOp::create(rewriter, forOp.getLoc(), innerWarp.getResults());

// Update the users of original `WarpOp` results that were coming from the
// Update the users of the new `WarpOp` results that were coming from the
// original `ForOp` to the corresponding new `ForOp` result.
for (auto [origIdx, newIdx] : forResultMapping)
rewriter.replaceAllUsesExcept(warpOp.getResult(origIdx),
rewriter.replaceAllUsesExcept(newWarpOp.getResult(origIdx),
newForOp.getResult(newIdx), newForOp);
// Similarly, update any users of the `WarpOp` results that were not
// results of the `ForOp`.
for (auto [origIdx, newIdx] : nonForResultMapping)
rewriter.replaceAllUsesWith(warpOp.getResult(origIdx),
newWarpOp.getResult(newIdx));
// Remove the original `WarpOp` and `ForOp`, they should not have any uses
// at this point.
rewriter.eraseOp(forOp);
rewriter.eraseOp(warpOp);
// Update any users of escaping values that were forwarded to the
// inner `WarpOp`. These values are now arguments of the inner `WarpOp`.
newForOp.walk([&](Operation *op) {
Expand Down
19 changes: 19 additions & 0 deletions mlir/test/Dialect/Vector/vector-warp-distribute.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -1925,3 +1925,22 @@ func.func @warp_scf_if_distribute(%pred : i1) {
// CHECK-PROP: "some_use"(%[[IF_YIELD_DIST]]) : (vector<1xf32>) -> ()
// CHECK-PROP: return
// CHECK-PROP: }

// -----
func.func @dedup_unused_result(%laneid : index) -> (vector<1xf32>) {
%r:3 = gpu.warp_execute_on_lane_0(%laneid)[32] ->
(vector<1xf32>, vector<2xf32>, vector<1xf32>) {
%2 = "some_def"() : () -> (vector<32xf32>)
%3 = "some_def"() : () -> (vector<64xf32>)
gpu.yield %2, %3, %2 : vector<32xf32>, vector<64xf32>, vector<32xf32>
}
%r0 = "some_use"(%r#2, %r#2) : (vector<1xf32>, vector<1xf32>) -> (vector<1xf32>)
return %r0 : vector<1xf32>
}

// CHECK-PROP: func @dedup_unused_result
// CHECK-PROP: %[[R:.*]] = gpu.warp_execute_on_lane_0(%arg0)[32] -> (vector<1xf32>)
// CHECK-PROP: %[[Y0:.*]] = "some_def"() : () -> vector<32xf32>
// CHECK-PROP: %[[Y1:.*]] = "some_def"() : () -> vector<64xf32>
// CHECK-PROP: gpu.yield %[[Y0]] : vector<32xf32>
// CHECK-PROP: "some_use"(%[[R]], %[[R]]) : (vector<1xf32>, vector<1xf32>) -> vector<1xf32>