[MLIR][Affine] Fix fusion private memref creation for multiple producer stores #130365
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…er stores Fix private memref creation in affine fusion for the multiple producer store case. This scenario was not supported but not properly checked. Fixes: llvm#120227
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@llvm/pr-subscribers-mlir-affine @llvm/pr-subscribers-mlir Author: Uday Bondhugula (bondhugula) ChangesFix private memref creation in affine fusion for the multiple producer store Fixes: #120227 Full diff: https://github.com/llvm/llvm-project/pull/130365.diff 3 Files Affected:
diff --git a/mlir/lib/Dialect/Affine/Transforms/LoopFusion.cpp b/mlir/lib/Dialect/Affine/Transforms/LoopFusion.cpp
index 21cd0e2e49c2a..bcba17bb21544 100644
--- a/mlir/lib/Dialect/Affine/Transforms/LoopFusion.cpp
+++ b/mlir/lib/Dialect/Affine/Transforms/LoopFusion.cpp
@@ -328,7 +328,9 @@ static std::optional<double> getAdditionalComputeFraction(
// Creates and returns a private (single-user) memref for fused loop rooted at
// 'forOp', with (potentially reduced) memref size based on the memref region
// written to by `storeOps` at depth 'dstLoopDepth'. 'sliceInsertionBlock'
-// specifies the block in which the slice was/will be inserted.
+// specifies the block in which the slice was/will be inserted. The method
+// expects that all stores ops to the memref have the same access function.
+// Returns nullptr if the creation failed.
static Value createPrivateMemRef(AffineForOp forOp,
ArrayRef<Operation *> storeOps,
unsigned dstLoopDepth,
@@ -336,6 +338,24 @@ static Value createPrivateMemRef(AffineForOp forOp,
Block *sliceInsertionBlock,
uint64_t localBufSizeThreshold) {
assert(!storeOps.empty() && "no source stores supplied");
+
+ // Check if all stores have the same access function; we only support this
+ // case.
+ // TODO: Use union of memref write regions to compute private memref footprint
+ // for store ops with different access functions.
+ if (storeOps.size() > 1 &&
+ !std::equal(std::next(storeOps.begin()), storeOps.end(), storeOps.begin(),
+ [](Operation *a, Operation *b) {
+ MemRefAccess aM(cast<AffineWriteOpInterface>(a));
+ MemRefAccess bM(cast<AffineWriteOpInterface>(b));
+ return aM == bM;
+ })) {
+ LLVM_DEBUG(llvm::dbgs()
+ << "Private memref creation unsupported for multiple producer "
+ "stores with different access functions.\n");
+ return nullptr;
+ }
+
Operation *srcStoreOp = storeOps[0];
// Create builder to insert alloc op just before 'forOp'.
@@ -432,6 +452,8 @@ static Value createPrivateMemRef(AffineForOp forOp,
assert(succeeded(res) &&
"replaceAllMemrefUsesWith should always succeed here");
(void)res;
+ LLVM_DEBUG(llvm::dbgs() << "Created private memref of type: " << newMemRefType
+ << '\n');
return newMemRef;
}
@@ -1123,13 +1145,12 @@ struct GreedyFusion {
// loads and stores. Any reference to the original ones becomes
// invalid after this point.
for (auto &memrefToStoresPair : privateMemRefToStores) {
- // TODO: Use union of memref write regions to compute
- // private memref footprint.
- SmallVector<Operation *, 4> &storesForMemref =
- memrefToStoresPair.second;
+ ArrayRef<Operation *> storesForMemref = memrefToStoresPair.second;
Value newMemRef = createPrivateMemRef(
dstAffineForOp, storesForMemref, bestDstLoopDepth,
fastMemorySpace, sliceInsertionBlock, localBufSizeThreshold);
+ if (!newMemRef)
+ continue;
// Create new node in dependence graph for 'newMemRef' alloc op.
unsigned newMemRefNodeId = mdg->addNode(newMemRef.getDefiningOp());
// Add edge from 'newMemRef' node to dstNode.
diff --git a/mlir/test/Dialect/Affine/loop-fusion-2.mlir b/mlir/test/Dialect/Affine/loop-fusion-2.mlir
index 9648504b7f960..b26a539b2f7d5 100644
--- a/mlir/test/Dialect/Affine/loop-fusion-2.mlir
+++ b/mlir/test/Dialect/Affine/loop-fusion-2.mlir
@@ -39,16 +39,20 @@ func.func @should_fuse_at_depth_above_loop_carried_dependence(%arg0: memref<64x4
// We can fuse source loop nest '%i0' into dst loop nest '%i2', but the
// depth at which we can insert the src loop nest slice into the dst loop
- // lest must be decreased because of a loop carried dependence on loop '%i3'.
+ // nest must be decreased because of a loop carried dependence on loop '%i3'.
// As a result, the source loop nest is inserted at dst loop nest depth 1,
// just above the loop with the carried dependence. In addition, the source
// loop nest iteration bounds on its loop '%i1' are reduced to 1, so the
- // memref size can be reduced to 128x1xf32.
+ // memref size can be reduced to 64x1xf32.
- // CHECK: memref.alloc() : memref<64x1xf32>
+ // In this case, since we have multiple producer stores (for %out) with
+ // different access functions and we don't yet support private memref
+ // computation in such cases, a 64x1 private memref isn't created.
+
+ // CHECK: memref.alloc() : memref<64x4xf32>
// CHECK: affine.for %{{.*}} = 0 to 4 {
// CHECK-NEXT: affine.for %{{.*}} = 0 to 64 {
- // CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}, 0] : memref<64x1xf32>
+ // CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}, %{{.*}}] : memref<64x4xf32>
// CHECK-NEXT: }
// CHECK-NEXT: affine.for %{{.*}} = 0 to 4 {
// CHECK-NEXT: affine.for %{{.*}} = 0 to 16 {
@@ -62,9 +66,9 @@ func.func @should_fuse_at_depth_above_loop_carried_dependence(%arg0: memref<64x4
// CHECK-NEXT: }
// CHECK-NEXT: affine.for %{{.*}} = 0 to 16 {
// CHECK-NEXT: %{{.*}} = "op2"() : () -> f32
- // CHECK: affine.load %{{.*}}[%{{.*}} * 16 + %{{.*}}, 0] : memref<64x1xf32>
+ // CHECK: affine.load %{{.*}}[%{{.*}} * 16 + %{{.*}}, %{{.*}}] : memref<64x4xf32>
// CHECK-NEXT: arith.addf %{{.*}}, %{{.*}} : f32
- // CHECK: affine.store %{{.*}}, %{{.*}}[%{{.*}} * 16 + %{{.*}}, 0] : memref<64x1xf32>
+ // CHECK: affine.store %{{.*}}, %{{.*}}[%{{.*}} * 16 + %{{.*}}, %{{.*}}] : memref<64x4xf32>
// CHECK-NEXT: }
// CHECK-NEXT: }
// CHECK-NEXT: }
diff --git a/mlir/test/Dialect/Affine/loop-fusion-4.mlir b/mlir/test/Dialect/Affine/loop-fusion-4.mlir
index b5b951ad5eb0e..4b9eca45492fb 100644
--- a/mlir/test/Dialect/Affine/loop-fusion-4.mlir
+++ b/mlir/test/Dialect/Affine/loop-fusion-4.mlir
@@ -622,3 +622,47 @@ func.func @zero_tolerance(%arg0: memref<65536xcomplex<f64>>, %arg1: memref<30x13
}
func.func private @__external_levelwise_forward_ntt(memref<30x131072xi64>)
func.func private @__external_reduce_barrett(i64, i64, i64, i64, i128) -> i64
+
+// An unrolled loop nest. Fusion here should correctly fuse while preserving
+// dependences between store-load pairs of the same memref. A private memref
+// of size 1x1x1 can't be created.
+
+// PRODUCER-CONSUMER-MAXIMAL-LABEL: func @unrolled
+func.func @unrolled(%arg0: memref<2x4xf32>, %arg1: memref<1x2x4xf32>) {
+ %alloc = memref.alloc() : memref<1x2x4xf32>
+ affine.for %i = 0 to 1 {
+ %0 = affine.load %arg0[0, 0] : memref<2x4xf32>
+ %1 = affine.load %arg0[0, 1] : memref<2x4xf32>
+ %2 = affine.load %arg0[0, 2] : memref<2x4xf32>
+ %3 = affine.load %arg0[0, 3] : memref<2x4xf32>
+ %4 = affine.load %arg0[1, 0] : memref<2x4xf32>
+ %5 = affine.load %arg0[1, 1] : memref<2x4xf32>
+ %6 = affine.load %arg0[1, 2] : memref<2x4xf32>
+ %7 = affine.load %arg0[1, 3] : memref<2x4xf32>
+
+ affine.store %0, %alloc[0, 0, 0] : memref<1x2x4xf32>
+ affine.store %1, %alloc[0, 0, 1] : memref<1x2x4xf32>
+ affine.store %2, %alloc[0, 0, 2] : memref<1x2x4xf32>
+ affine.store %3, %alloc[0, 0, 3] : memref<1x2x4xf32>
+ affine.store %4, %alloc[0, 1, 0] : memref<1x2x4xf32>
+ affine.store %5, %alloc[0, 1, 1] : memref<1x2x4xf32>
+ affine.store %6, %alloc[0, 1, 2] : memref<1x2x4xf32>
+ affine.store %7, %alloc[0, 1, 3] : memref<1x2x4xf32>
+ }
+
+ affine.for %i = 0 to 2 {
+ affine.for %j = 0 to 4 {
+ %8 = affine.load %alloc[0, %i, %j] : memref<1x2x4xf32>
+ %9 = arith.negf %8 : f32
+ affine.store %9, %arg1[0, %i, %j] : memref<1x2x4xf32>
+ }
+ }
+ // PRODUCER-CONSUMER-MAXIMAL: affine.for %{{.*}} = 0 to 2 {
+ // PRODUCER-CONSUMER-MAXIMAL-NEXT: affine.for %{{.*}} = 0 to 4 {
+ // PRODUCER-CONSUMER-MAXIMAL-NEXT: affine.load %{{.*}}[0, 0]
+ // PRODUCER-CONSUMER-MAXIMAL: affine.load %{{.*}}[1, 3]
+ // PRODUCER-CONSUMER-MAXIMAL: affine.store %{{.*}}[0, 0, 0]
+ // PRODUCER-CONSUMER-MAXIMAL: affine.store %{{.*}}[0, 1, 3]
+ // PRODUCER-CONSUMER-MAXIMAL: affine.load %{{.*}}[0, %{{.*}}, %{{.*}}]
+ return
+}
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Fix private memref creation in affine fusion for the multiple producer store
case. This scenario was not supported but not properly checked.
Fixes: #120227