[Mlir-commits] [mlir] ddeb55a - [mlir] add option to multi-buffering
Thomas Raoux
llvmlistbot at llvm.org
Fri Feb 17 07:35:11 PST 2023
Author: Thomas Raoux
Date: 2023-02-17T15:34:51Z
New Revision: ddeb55ab3359a7e332db47afaf0c574adf1a147a
URL: https://github.com/llvm/llvm-project/commit/ddeb55ab3359a7e332db47afaf0c574adf1a147a
DIFF: https://github.com/llvm/llvm-project/commit/ddeb55ab3359a7e332db47afaf0c574adf1a147a.diff
LOG: [mlir] add option to multi-buffering
Allow user to apply multi-buffering transformation for cases where proving
that there is no loop carried dependency is not trivial. In this case user needs
to ensure that the data are written and read in the same iteration otherwise the
result is incorrect.
Differential Revision: https://reviews.llvm.org/D144227
Added:
Modified:
mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td
mlir/include/mlir/Dialect/MemRef/Transforms/Passes.h
mlir/lib/Dialect/MemRef/TransformOps/MemRefTransformOps.cpp
mlir/lib/Dialect/MemRef/Transforms/MultiBuffer.cpp
mlir/test/Dialect/MemRef/transform-ops.mlir
Removed:
################################################################################
diff --git a/mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td b/mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td
index c22cec855f13a..ea7784eec0d36 100644
--- a/mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td
+++ b/mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td
@@ -28,6 +28,9 @@ def MemRefMultiBufferOp : Op<Transform_Dialect, "memref.multibuffer",
iterations. This transform expands the size of an allocation by
a given multiplicative factor and fixes up any users of the
multibuffered allocation.
+ If skip analysis is not set the transformation will only apply
+ if it can prove that there is no data being carried across loop
+ iterations.
#### Return modes
@@ -37,7 +40,8 @@ def MemRefMultiBufferOp : Op<Transform_Dialect, "memref.multibuffer",
let arguments =
(ins Transform_MemRefAllocOp:$target,
- ConfinedAttr<I64Attr, [IntPositive]>:$factor);
+ ConfinedAttr<I64Attr, [IntPositive]>:$factor,
+ UnitAttr:$skip_analysis);
let results = (outs PDL_Operation:$transformed);
diff --git a/mlir/include/mlir/Dialect/MemRef/Transforms/Passes.h b/mlir/include/mlir/Dialect/MemRef/Transforms/Passes.h
index 8935650eed9c9..80ecc10f4adfb 100644
--- a/mlir/include/mlir/Dialect/MemRef/Transforms/Passes.h
+++ b/mlir/include/mlir/Dialect/MemRef/Transforms/Passes.h
@@ -78,7 +78,10 @@ void populateMemRefWideIntEmulationConversions(
/// on the temporary allocation between consecutive loop iterations.
/// It returns the new allocation if the original allocation was multi-buffered
/// and returns failure() otherwise.
-/// Example:
+/// When `skipOverrideAnalysis`, the pass will apply the transformation
+/// without checking thwt the buffer is overrided at the beginning of each
+/// iteration. This implies that user knows that there is no data carried across
+/// loop iterations. Example:
/// ```
/// %0 = memref.alloc() : memref<4x128xf32>
/// scf.for %iv = %c1 to %c1024 step %c3 {
@@ -100,7 +103,8 @@ void populateMemRefWideIntEmulationConversions(
/// }
/// ```
FailureOr<memref::AllocOp> multiBuffer(memref::AllocOp allocOp,
- unsigned multiplier);
+ unsigned multiplier,
+ bool skipOverrideAnalysis = false);
//===----------------------------------------------------------------------===//
// Passes
diff --git a/mlir/lib/Dialect/MemRef/TransformOps/MemRefTransformOps.cpp b/mlir/lib/Dialect/MemRef/TransformOps/MemRefTransformOps.cpp
index 85356d294973f..e4b3b4523ac7a 100644
--- a/mlir/lib/Dialect/MemRef/TransformOps/MemRefTransformOps.cpp
+++ b/mlir/lib/Dialect/MemRef/TransformOps/MemRefTransformOps.cpp
@@ -41,7 +41,8 @@ DiagnosedSilenceableFailure transform::MemRefMultiBufferOp::apply(
if (!canApplyMultiBuffer)
continue;
- auto newBuffer = memref::multiBuffer(target, getFactor());
+ auto newBuffer =
+ memref::multiBuffer(target, getFactor(), getSkipAnalysis());
if (failed(newBuffer))
return emitSilenceableFailure(target->getLoc())
<< "op failed to multibuffer";
diff --git a/mlir/lib/Dialect/MemRef/Transforms/MultiBuffer.cpp b/mlir/lib/Dialect/MemRef/Transforms/MultiBuffer.cpp
index e094f5a5d454d..c93bda2e0be25 100644
--- a/mlir/lib/Dialect/MemRef/Transforms/MultiBuffer.cpp
+++ b/mlir/lib/Dialect/MemRef/Transforms/MultiBuffer.cpp
@@ -82,8 +82,9 @@ static Value getOrCreateValue(OpFoldResult res, OpBuilder &builder,
// Returns success if the transformation happened and failure otherwise.
// This is not a pattern as it requires propagating the new memref type to its
// uses and requires updating subview ops.
-FailureOr<memref::AllocOp> mlir::memref::multiBuffer(memref::AllocOp allocOp,
- unsigned multiplier) {
+FailureOr<memref::AllocOp>
+mlir::memref::multiBuffer(memref::AllocOp allocOp, unsigned multiplier,
+ bool skipOverrideAnalysis) {
LLVM_DEBUG(DBGS() << "Try multibuffer: " << allocOp << "\n");
DominanceInfo dom(allocOp->getParentOp());
LoopLikeOpInterface candidateLoop;
@@ -93,17 +94,29 @@ FailureOr<memref::AllocOp> mlir::memref::multiBuffer(memref::AllocOp allocOp,
LLVM_DEBUG(DBGS() << "Skip user: no parent loop\n");
return failure();
}
- /// Make sure there is no loop-carried dependency on the allocation.
- if (!overrideBuffer(user, allocOp.getResult())) {
- LLVM_DEBUG(DBGS() << "Skip user: found loop-carried dependence\n");
- continue;
- }
- // If this user doesn't dominate all the other users keep looking.
- if (llvm::any_of(allocOp->getUsers(), [&](Operation *otherUser) {
- return !dom.dominates(user, otherUser);
- })) {
- LLVM_DEBUG(DBGS() << "Skip user: does not dominate all other users\n");
- continue;
+ if (!skipOverrideAnalysis) {
+ /// Make sure there is no loop-carried dependency on the allocation.
+ if (!overrideBuffer(user, allocOp.getResult())) {
+ LLVM_DEBUG(DBGS() << "Skip user: found loop-carried dependence\n");
+ continue;
+ }
+ // If this user doesn't dominate all the other users keep looking.
+ if (llvm::any_of(allocOp->getUsers(), [&](Operation *otherUser) {
+ return !dom.dominates(user, otherUser);
+ })) {
+ LLVM_DEBUG(DBGS() << "Skip user: does not dominate all other users\n");
+ continue;
+ }
+ } else {
+ if (llvm::any_of(allocOp->getUsers(), [&](Operation *otherUser) {
+ return !isa<memref::DeallocOp>(otherUser) &&
+ !parentLoop->isProperAncestor(otherUser);
+ })) {
+ LLVM_DEBUG(
+ DBGS()
+ << "Skip user: not all other users are in the parent loop\n");
+ continue;
+ }
}
candidateLoop = parentLoop;
break;
diff --git a/mlir/test/Dialect/MemRef/transform-ops.mlir b/mlir/test/Dialect/MemRef/transform-ops.mlir
index df25fec4b1c75..450e642913cf1 100644
--- a/mlir/test/Dialect/MemRef/transform-ops.mlir
+++ b/mlir/test/Dialect/MemRef/transform-ops.mlir
@@ -185,3 +185,37 @@ transform.sequence failures(propagate) {
// Verify that the returned handle is usable.
transform.test_print_remark_at_operand %1, "transformed" : !pdl.operation
}
+
+// -----
+
+
+// CHECK-DAG: #[[$MAP0:.*]] = affine_map<(d0) -> ((d0 floordiv 4) mod 2)>
+
+// CHECK-LABEL: func @multi_buffer
+func.func @multi_buffer_no_analysis(%in: memref<16xf32>) {
+ // CHECK: %[[A:.*]] = memref.alloc() : memref<2x4xf32>
+ // expected-remark @below {{transformed}}
+ %tmp = memref.alloc() : memref<4xf32>
+
+ // CHECK: %[[C0:.*]] = arith.constant 0 : index
+ // CHECK: %[[C4:.*]] = arith.constant 4 : index
+ %c0 = arith.constant 0 : index
+ %c4 = arith.constant 4 : index
+ %c16 = arith.constant 16 : index
+
+ // CHECK: scf.for %[[IV:.*]] = %[[C0]]
+ scf.for %i0 = %c0 to %c16 step %c4 {
+ // CHECK: %[[I:.*]] = affine.apply #[[$MAP0]](%[[IV]])
+ // CHECK: %[[SV:.*]] = memref.subview %[[A]][%[[I]], 0] [1, 4] [1, 1] : memref<2x4xf32> to memref<4xf32, strided<[1], offset: ?>>
+ "some_write_read"(%tmp) : (memref<4xf32>) ->()
+ }
+ return
+}
+
+transform.sequence failures(propagate) {
+^bb1(%arg1: !pdl.operation):
+ %0 = transform.structured.match ops{["memref.alloc"]} in %arg1 : (!pdl.operation) -> !transform.op<"memref.alloc">
+ %1 = transform.memref.multibuffer %0 {factor = 2 : i64, skip_analysis} : (!transform.op<"memref.alloc">) -> !pdl.operation
+ // Verify that the returned handle is usable.
+ transform.test_print_remark_at_operand %1, "transformed" : !pdl.operation
+}
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