[mlir][bufferization] Ownership-based deallocation: Allow manual (de)allocs #68648
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…allocs Add a new attribute `bufferization.manual_deallocation` that can be attached to allocation and deallocation ops. Buffers that are allocated with this attribute are assigned an ownership of "false". Such buffers can be deallocated manually (e.g., with `memref.dealloc`) if the deallocation op also has the attribute set. Previously, the ownership-based buffer deallocation pass used to reject IR with existing deallocation ops. This is no longer the case if such ops have this new attribute. This change is useful for the sparse compiler, which currently deallocates the sparse tensor buffers by itself.
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@llvm/pr-subscribers-mlir @llvm/pr-subscribers-mlir-bufferization Author: Matthias Springer (matthias-springer) ChangesAdd a new attribute This change is useful for the sparse compiler, which currently deallocates the sparse tensor buffers by itself. Full diff: https://github.com/llvm/llvm-project/pull/68648.diff 5 Files Affected:
diff --git a/mlir/include/mlir/Dialect/Bufferization/IR/BufferizationBase.td b/mlir/include/mlir/Dialect/Bufferization/IR/BufferizationBase.td
index 0d509e69349e918..818e931aeb5054c 100644
--- a/mlir/include/mlir/Dialect/Bufferization/IR/BufferizationBase.td
+++ b/mlir/include/mlir/Dialect/Bufferization/IR/BufferizationBase.td
@@ -60,6 +60,17 @@ def Bufferization_Dialect : Dialect {
/// arguments during One-Shot Module Bufferize.
constexpr const static ::llvm::StringLiteral
kBufferLayoutAttrName = "bufferization.buffer_layout";
+
+ /// An attribute that can be attached to ops with an allocation and/or
+ /// deallocation side effect. It indicates that the op is under a "manual
+ /// deallocation" scheme. In the case of an allocation op, the returned
+ /// value is *not* an automatically managed allocation and assigned an
+ /// ownership of "false". Furthermore, only deallocation ops that are
+ /// guaranteed to deallocate a buffer under "manual deallocation" are
+ /// allowed to have this attribute. (Deallocation ops without this
+ /// attribute are rejected by the ownership-based buffer deallocation pass.)
+ constexpr const static ::llvm::StringLiteral
+ kManualDeallocation = "bufferization.manual_deallocation";
}];
let hasOperationAttrVerify = 1;
}
diff --git a/mlir/lib/Dialect/Bufferization/IR/BufferizationDialect.cpp b/mlir/lib/Dialect/Bufferization/IR/BufferizationDialect.cpp
index 802bd52269419b4..e5a0c3c45b09e2f 100644
--- a/mlir/lib/Dialect/Bufferization/IR/BufferizationDialect.cpp
+++ b/mlir/lib/Dialect/Bufferization/IR/BufferizationDialect.cpp
@@ -28,6 +28,16 @@ constexpr const ::llvm::StringLiteral BufferizationDialect::kWritableAttrName;
constexpr const ::llvm::StringLiteral
BufferizationDialect::kBufferLayoutAttrName;
+/// An attribute that can be attached to ops with an allocation and/or
+/// deallocation side effect. It indicates that the op is under a "manual
+/// deallocation" scheme. In the case of an allocation op, the returned
+/// value is *not* an automatically managed allocation and assigned an
+/// ownership of "false". Furthermore, only deallocation ops that are
+/// guaranteed to deallocate a buffer under "manual deallocation" are
+/// allowed to have this attribute. (Deallocation ops without this
+/// attribute are rejected by the ownership-based buffer deallocation pass.)
+constexpr const ::llvm::StringLiteral BufferizationDialect::kManualDeallocation;
+
//===----------------------------------------------------------------------===//
// Bufferization Dialect Interfaces
//===----------------------------------------------------------------------===//
@@ -105,6 +115,16 @@ BufferizationDialect::verifyOperationAttribute(Operation *op,
NamedAttribute attr) {
using bufferization::BufferizableOpInterface;
+ if (attr.getName() == kManualDeallocation) {
+ if (!mlir::hasEffect<MemoryEffects::Allocate>(op) &&
+ !mlir::hasEffect<MemoryEffects::Free>(op))
+ return op->emitOpError("attribute '")
+ << kManualDeallocation
+ << "' can be used only on ops that have an allocation and/or free "
+ "side effect";
+ return success();
+ }
+
return op->emitError()
<< "attribute '" << attr.getName()
<< "' not supported as an op attribute by the bufferization dialect";
diff --git a/mlir/lib/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation.cpp b/mlir/lib/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation.cpp
index fd36716163d0ad4..b2b77eda92ef210 100644
--- a/mlir/lib/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation.cpp
+++ b/mlir/lib/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation.cpp
@@ -21,6 +21,7 @@
#include "mlir/Dialect/Bufferization/IR/BufferDeallocationOpInterface.h"
#include "mlir/Dialect/Bufferization/IR/Bufferization.h"
#include "mlir/Dialect/Bufferization/Transforms/Passes.h"
+#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
@@ -856,13 +857,32 @@ FailureOr<Operation *> BufferDeallocation::handleInterface(CallOpInterface op) {
FailureOr<Operation *>
BufferDeallocation::handleInterface(MemoryEffectOpInterface op) {
auto *block = op->getBlock();
+ OpBuilder builder = OpBuilder::atBlockBegin(block);
- for (auto operand : llvm::make_filter_range(op->getOperands(), isMemref))
- if (op.getEffectOnValue<MemoryEffects::Free>(operand).has_value())
- return op->emitError(
- "memory free side-effect on MemRef value not supported!");
+ for (auto operand : llvm::make_filter_range(op->getOperands(), isMemref)) {
+ if (op.getEffectOnValue<MemoryEffects::Free>(operand).has_value()) {
+ if (!op->hasAttr(BufferizationDialect::kManualDeallocation))
+ return op->emitError(
+ "memory free side-effect on MemRef value not supported!");
+
+ // Buffers that were allocated under "manual deallocation" may be
+ // manually deallocated. We insert a runtime assertion to cover certain
+ // cases of invalid IR where an automatically managed buffer allocation
+ // is manually deallocated. This is not a bulletproof check!
+ OpBuilder::InsertionGuard g(builder);
+ builder.setInsertionPoint(op);
+ Ownership ownership = state.getOwnership(operand, block);
+ if (ownership.isUnique()) {
+ Value ownershipInverted = builder.create<arith::XOrIOp>(
+ op.getLoc(), ownership.getIndicator(),
+ buildBoolValue(builder, op.getLoc(), true));
+ builder.create<cf::AssertOp>(
+ op.getLoc(), ownershipInverted,
+ "expected that the block does not have ownership");
+ }
+ }
+ }
- OpBuilder builder = OpBuilder::atBlockBegin(block);
for (auto res : llvm::make_filter_range(op->getResults(), isMemref)) {
auto allocEffect = op.getEffectOnValue<MemoryEffects::Allocate>(res);
if (allocEffect.has_value()) {
@@ -880,6 +900,15 @@ BufferDeallocation::handleInterface(MemoryEffectOpInterface op) {
continue;
}
+ if (op->hasAttr(BufferizationDialect::kManualDeallocation)) {
+ // This allocation will be deallocated manually. Assign an ownership of
+ // "false", so that it will never be deallocated by the buffer
+ // deallocation pass.
+ state.resetOwnerships(res, block);
+ state.updateOwnership(res, buildBoolValue(builder, op.getLoc(), false));
+ continue;
+ }
+
state.updateOwnership(res, buildBoolValue(builder, op.getLoc(), true));
state.addMemrefToDeallocate(res, block);
}
diff --git a/mlir/test/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation/dealloc-memoryeffect-interface.mlir b/mlir/test/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation/dealloc-memoryeffect-interface.mlir
index 44cf16385603e07..40a57b90c6e994f 100644
--- a/mlir/test/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation/dealloc-memoryeffect-interface.mlir
+++ b/mlir/test/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation/dealloc-memoryeffect-interface.mlir
@@ -124,3 +124,35 @@ func.func @op_without_aliasing_and_allocation() -> memref<4xf32> {
// CHECK: [[CLONE:%.+]] = bufferization.clone [[GLOBAL]]
// CHECK: scf.yield [[CLONE]] :
// CHECK: return [[RES]] :
+
+// -----
+
+// Allocations with "bufferization.manual_deallocation" are assigned an
+// ownership of "false".
+
+func.func @manual_deallocation(%c: i1, %f: f32, %idx: index) -> f32 {
+ %0 = memref.alloc() {bufferization.manual_deallocation} : memref<5xf32>
+ linalg.fill ins(%f : f32) outs(%0 : memref<5xf32>)
+ %1 = memref.alloc() : memref<5xf32>
+ linalg.fill ins(%f : f32) outs(%1 : memref<5xf32>)
+ %2 = arith.select %c, %0, %1 : memref<5xf32>
+ %3 = memref.load %2[%idx] : memref<5xf32>
+
+ // Only buffers that are under "manual deallocation" are allowed to be
+ // deallocated with memref.dealloc. For consistency reasons, the
+ // manual_deallocation attribute must also be specified. A runtime insertion
+ // is inserted to ensure that we do not have ownership. (This is not a
+ // bulletproof check, but covers some cases of invalid IR.)
+ memref.dealloc %0 {bufferization.manual_deallocation} : memref<5xf32>
+
+ return %3 : f32
+}
+
+// CHECK-LABEL: func @manual_deallocation(
+// CHECK: %[[true:.*]] = arith.constant true
+// CHECK: %[[manual_alloc:.*]] = memref.alloc() {bufferization.manual_deallocation} : memref<5xf32>
+// CHECK: %[[managed_alloc:.*]] = memref.alloc() : memref<5xf32>
+// CHECK: %[[selected:.*]] = arith.select
+// CHECK: cf.assert %[[true]], "expected that the block does not have ownership"
+// CHECK: memref.dealloc %[[manual_alloc]]
+// CHECK: bufferization.dealloc (%[[managed_alloc]] : memref<5xf32>) if (%[[true]])
diff --git a/mlir/test/Dialect/Bufferization/invalid.mlir b/mlir/test/Dialect/Bufferization/invalid.mlir
index ce56f89c1f1bbe6..912860c0d557026 100644
--- a/mlir/test/Dialect/Bufferization/invalid.mlir
+++ b/mlir/test/Dialect/Bufferization/invalid.mlir
@@ -143,3 +143,10 @@ func.func @invalid_dealloc_wrong_number_of_results(%arg0: memref<2xf32>, %arg1:
%0:3 = "bufferization.dealloc"(%arg0, %arg1, %arg2, %arg2, %arg1) <{operandSegmentSizes = array<i32: 2, 2, 1>}> : (memref<2xf32>, memref<4xi32>, i1, i1, memref<4xi32>) -> (i1, i1, i1)
return %0#0 : i1
}
+
+// -----
+
+func.func @invalid_manual_deallocation() {
+ // expected-error @below{{op attribute 'bufferization.manual_deallocation' can be used only on ops that have an allocation and/or free side effect}}
+ arith.constant {bufferization.manual_deallocation} 0 : index
+}
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aartbik
approved these changes
Oct 18, 2023
joker-eph
reviewed
Jan 3, 2024
| if (op.getEffectOnValue<MemoryEffects::Free>(operand).has_value()) { | ||
| if (!op->hasAttr(BufferizationDialect::kManualDeallocation)) | ||
| return op->emitError( | ||
| "memory free side-effect on MemRef value not supported!"); |
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I don't quite get this message here? It does not seems to relate to the conditions that lead here, or am I missing something?
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This is one of the things that confused me in #72289.
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The buffer deallocation pass fails if there are any "free" side effects (memory deallocations) in the input IR. We cannot handle such input programs at the moment.
There is one exception: Existing buffer deallocation ops are allowed if they are annotated with bufferization.manual_deallocation. The corresponding allocation must then also be annotated with that attribute. The buffer deallocation pass can completely ignore such buffers. (Internally, they are assigned an ownership indicator of "false".)
In essence, bufferization.manual_deallocation is a way exclude parts of the input IR from the buffer deallocation pass.
The code here checks if the op has a free side effect. If that is the case and there is no manual_deallocation attribute on the op, we reject the IR.
aartbik
reviewed
Jan 4, 2024
| @@ -28,6 +28,16 @@ constexpr const ::llvm::StringLiteral BufferizationDialect::kWritableAttrName; | |||
| constexpr const ::llvm::StringLiteral | |||
| BufferizationDialect::kBufferLayoutAttrName; | |||
|
|
|||
| /// An attribute that can be attached to ops with an allocation and/or | |||
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do we want to repeat the doc in both td and cpp ?
matthias-springer
added a commit
to matthias-springer/llvm-project
that referenced
this pull request
Jan 4, 2024
…eInterface` This is a follow-up for llvm#68648.
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Add a new attribute
bufferization.manual_deallocationthat can be attached to allocation and deallocation ops. Buffers that are allocated with this attribute are assigned an ownership of "false". Such buffers can be deallocated manually (e.g., withmemref.dealloc) if the deallocation op also has the attribute set. Previously, the ownership-based buffer deallocation pass used to reject IR with existing deallocation ops. This is no longer the case if such ops have this new attribute.This change is useful for the sparse compiler, which currently deallocates the sparse tensor buffers by itself.