[mlir][IR] Add Block::isReachable helper function
#114928
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Add a new helper function `isReachable` to `Block`. This function traverses all successors of a block to determine if another block is reachable from the current block. This functionality has been reimplemented in multiple places.
matthias-springer
requested review from
banach-space,
dcaballe,
hanhanW and
nicolasvasilache
as code owners
llvmbot
added
mlir:core
|
@llvm/pr-subscribers-mlir @llvm/pr-subscribers-mlir-core Author: Matthias Springer (matthias-springer) ChangesAdd a new helper function This functionality has been reimplemented in multiple places in MLIR. Possibly additional copies in downstream projects. Therefore, moving it to a common place. Full diff: https://github.com/llvm/llvm-project/pull/114928.diff 4 Files Affected:
diff --git a/mlir/include/mlir/IR/Block.h b/mlir/include/mlir/IR/Block.h
index 536cbf9018e898..37fa8dfe90bf0d 100644
--- a/mlir/include/mlir/IR/Block.h
+++ b/mlir/include/mlir/IR/Block.h
@@ -264,6 +264,11 @@ class alignas(8) Block : public IRObjectWithUseList<BlockOperand>,
succ_iterator succ_end() { return getSuccessors().end(); }
SuccessorRange getSuccessors() { return SuccessorRange(this); }
+ /// Return "true" if there is a path from this block to the given block
+ /// (according to the successors relationship). Both blocks must be in the
+ /// same region. Paths that contain a block from `except` do not count.
+ bool isReachable(Block *other, ArrayRef<Block *> except = {});
+
//===--------------------------------------------------------------------===//
// Walkers
//===--------------------------------------------------------------------===//
diff --git a/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp b/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
index 829e954d53b259..d1e6acef324fbd 100644
--- a/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
+++ b/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
@@ -273,25 +273,6 @@ static bool happensBefore(Operation *a, Operation *b,
return false;
}
-static bool isReachable(Block *from, Block *to, ArrayRef<Block *> except) {
- DenseSet<Block *> visited;
- SmallVector<Block *> worklist;
- for (Block *succ : from->getSuccessors())
- worklist.push_back(succ);
- while (!worklist.empty()) {
- Block *next = worklist.pop_back_val();
- if (llvm::is_contained(except, next))
- continue;
- if (next == to)
- return true;
- if (!visited.insert(next).second)
- continue;
- for (Block *succ : next->getSuccessors())
- worklist.push_back(succ);
- }
- return false;
-}
-
/// Return `true` if op dominance can be used to rule out a read-after-write
/// conflicts based on the ordering of ops. Returns `false` if op dominance
/// cannot be used to due region-based loops.
@@ -427,8 +408,8 @@ static bool canUseOpDominanceDueToBlocks(OpOperand *uRead, OpOperand *uWrite,
Block *writeBlock = uWrite->getOwner()->getBlock();
for (Value def : definitions) {
Block *defBlock = def.getParentBlock();
- if (isReachable(readBlock, writeBlock, {defBlock}) &&
- isReachable(writeBlock, readBlock, {defBlock}))
+ if (readBlock->isReachable(writeBlock, {defBlock}) &&
+ writeBlock->isReachable(readBlock, {defBlock}))
return false;
}
diff --git a/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp b/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
index 3a30382114c8dc..bd5f06a3b46d42 100644
--- a/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
@@ -73,20 +73,7 @@ bool TransferOptimization::isReachable(Operation *start, Operation *dest) {
// Simple case where the start op dominate the destination.
if (dominators.dominates(start, dest))
return true;
- Block *startBlock = start->getBlock();
- Block *destBlock = dest->getBlock();
- SmallVector<Block *, 32> worklist(startBlock->succ_begin(),
- startBlock->succ_end());
- SmallPtrSet<Block *, 32> visited;
- while (!worklist.empty()) {
- Block *bb = worklist.pop_back_val();
- if (!visited.insert(bb).second)
- continue;
- if (dominators.dominates(bb, destBlock))
- return true;
- worklist.append(bb->succ_begin(), bb->succ_end());
- }
- return false;
+ return start->getBlock()->isReachable(dest->getBlock());
}
/// For transfer_write to overwrite fully another transfer_write must:
diff --git a/mlir/lib/IR/Block.cpp b/mlir/lib/IR/Block.cpp
index 65099f8ff15a6f..5ae98faaaba12c 100644
--- a/mlir/lib/IR/Block.cpp
+++ b/mlir/lib/IR/Block.cpp
@@ -7,9 +7,12 @@
//===----------------------------------------------------------------------===//
#include "mlir/IR/Block.h"
+
#include "mlir/IR/Builders.h"
#include "mlir/IR/Operation.h"
#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
+
using namespace mlir;
//===----------------------------------------------------------------------===//
@@ -331,7 +334,7 @@ unsigned PredecessorIterator::getSuccessorIndex() const {
}
//===----------------------------------------------------------------------===//
-// SuccessorRange
+// Successors
//===----------------------------------------------------------------------===//
SuccessorRange::SuccessorRange() : SuccessorRange(nullptr, 0) {}
@@ -349,6 +352,23 @@ SuccessorRange::SuccessorRange(Operation *term) : SuccessorRange() {
base = term->getBlockOperands().data();
}
+bool Block::isReachable(Block *other, ArrayRef<Block *> except) {
+ assert(getParent() == other->getParent() && "expected same region");
+ SmallVector<Block *> worklist(succ_begin(), succ_end());
+ SmallPtrSet<Block *, 16> visited;
+ while (!worklist.empty()) {
+ Block *next = worklist.pop_back_val();
+ if (llvm::is_contained(except, next))
+ continue;
+ if (next == other)
+ return true;
+ if (!visited.insert(next).second)
+ continue;
+ worklist.append(next->succ_begin(), next->succ_end());
+ }
+ return false;
+}
+
//===----------------------------------------------------------------------===//
// BlockRange
//===----------------------------------------------------------------------===//
|
|
@llvm/pr-subscribers-mlir-bufferization Author: Matthias Springer (matthias-springer) ChangesAdd a new helper function This functionality has been reimplemented in multiple places in MLIR. Possibly additional copies in downstream projects. Therefore, moving it to a common place. Full diff: https://github.com/llvm/llvm-project/pull/114928.diff 4 Files Affected:
diff --git a/mlir/include/mlir/IR/Block.h b/mlir/include/mlir/IR/Block.h
index 536cbf9018e898..37fa8dfe90bf0d 100644
--- a/mlir/include/mlir/IR/Block.h
+++ b/mlir/include/mlir/IR/Block.h
@@ -264,6 +264,11 @@ class alignas(8) Block : public IRObjectWithUseList<BlockOperand>,
succ_iterator succ_end() { return getSuccessors().end(); }
SuccessorRange getSuccessors() { return SuccessorRange(this); }
+ /// Return "true" if there is a path from this block to the given block
+ /// (according to the successors relationship). Both blocks must be in the
+ /// same region. Paths that contain a block from `except` do not count.
+ bool isReachable(Block *other, ArrayRef<Block *> except = {});
+
//===--------------------------------------------------------------------===//
// Walkers
//===--------------------------------------------------------------------===//
diff --git a/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp b/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
index 829e954d53b259..d1e6acef324fbd 100644
--- a/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
+++ b/mlir/lib/Dialect/Bufferization/Transforms/OneShotAnalysis.cpp
@@ -273,25 +273,6 @@ static bool happensBefore(Operation *a, Operation *b,
return false;
}
-static bool isReachable(Block *from, Block *to, ArrayRef<Block *> except) {
- DenseSet<Block *> visited;
- SmallVector<Block *> worklist;
- for (Block *succ : from->getSuccessors())
- worklist.push_back(succ);
- while (!worklist.empty()) {
- Block *next = worklist.pop_back_val();
- if (llvm::is_contained(except, next))
- continue;
- if (next == to)
- return true;
- if (!visited.insert(next).second)
- continue;
- for (Block *succ : next->getSuccessors())
- worklist.push_back(succ);
- }
- return false;
-}
-
/// Return `true` if op dominance can be used to rule out a read-after-write
/// conflicts based on the ordering of ops. Returns `false` if op dominance
/// cannot be used to due region-based loops.
@@ -427,8 +408,8 @@ static bool canUseOpDominanceDueToBlocks(OpOperand *uRead, OpOperand *uWrite,
Block *writeBlock = uWrite->getOwner()->getBlock();
for (Value def : definitions) {
Block *defBlock = def.getParentBlock();
- if (isReachable(readBlock, writeBlock, {defBlock}) &&
- isReachable(writeBlock, readBlock, {defBlock}))
+ if (readBlock->isReachable(writeBlock, {defBlock}) &&
+ writeBlock->isReachable(readBlock, {defBlock}))
return false;
}
diff --git a/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp b/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
index 3a30382114c8dc..bd5f06a3b46d42 100644
--- a/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/VectorTransferOpTransforms.cpp
@@ -73,20 +73,7 @@ bool TransferOptimization::isReachable(Operation *start, Operation *dest) {
// Simple case where the start op dominate the destination.
if (dominators.dominates(start, dest))
return true;
- Block *startBlock = start->getBlock();
- Block *destBlock = dest->getBlock();
- SmallVector<Block *, 32> worklist(startBlock->succ_begin(),
- startBlock->succ_end());
- SmallPtrSet<Block *, 32> visited;
- while (!worklist.empty()) {
- Block *bb = worklist.pop_back_val();
- if (!visited.insert(bb).second)
- continue;
- if (dominators.dominates(bb, destBlock))
- return true;
- worklist.append(bb->succ_begin(), bb->succ_end());
- }
- return false;
+ return start->getBlock()->isReachable(dest->getBlock());
}
/// For transfer_write to overwrite fully another transfer_write must:
diff --git a/mlir/lib/IR/Block.cpp b/mlir/lib/IR/Block.cpp
index 65099f8ff15a6f..5ae98faaaba12c 100644
--- a/mlir/lib/IR/Block.cpp
+++ b/mlir/lib/IR/Block.cpp
@@ -7,9 +7,12 @@
//===----------------------------------------------------------------------===//
#include "mlir/IR/Block.h"
+
#include "mlir/IR/Builders.h"
#include "mlir/IR/Operation.h"
#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
+
using namespace mlir;
//===----------------------------------------------------------------------===//
@@ -331,7 +334,7 @@ unsigned PredecessorIterator::getSuccessorIndex() const {
}
//===----------------------------------------------------------------------===//
-// SuccessorRange
+// Successors
//===----------------------------------------------------------------------===//
SuccessorRange::SuccessorRange() : SuccessorRange(nullptr, 0) {}
@@ -349,6 +352,23 @@ SuccessorRange::SuccessorRange(Operation *term) : SuccessorRange() {
base = term->getBlockOperands().data();
}
+bool Block::isReachable(Block *other, ArrayRef<Block *> except) {
+ assert(getParent() == other->getParent() && "expected same region");
+ SmallVector<Block *> worklist(succ_begin(), succ_end());
+ SmallPtrSet<Block *, 16> visited;
+ while (!worklist.empty()) {
+ Block *next = worklist.pop_back_val();
+ if (llvm::is_contained(except, next))
+ continue;
+ if (next == other)
+ return true;
+ if (!visited.insert(next).second)
+ continue;
+ worklist.append(next->succ_begin(), next->succ_end());
+ }
+ return false;
+}
+
//===----------------------------------------------------------------------===//
// BlockRange
//===----------------------------------------------------------------------===//
|
River707
requested changes
Nov 5, 2024
|
Coming back to this PR after reading #114940 (which uses this function). I don't think we should add this kind of thing to Block, I'd rather push people to use DominanceInfo (which does this more optimally). Things like Dialect Conversion (which make a muck of blocks and all kinds of other things) are generally very unique compared to the majority of users. For API's on the core data structures, the APIs should (generally) be pushing for the best way to do something. |
Block reachability and block dominance are two different things. Just because there is a path from That being said, in the dialect conversion I actually need dominance, so what I implemented here is not useful there... |
joker-eph
reviewed
Nov 6, 2024
joker-eph
reviewed
Nov 6, 2024
|
Seems fine to me but I'll let you finish the discussion with River though. |
matthias-springer
deleted the
users/matthias-springer/block_is_reachable
branch
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Add a new helper function
isReachabletoBlock. This function traverses all successors of a block to determine if another block is reachable from the current block.This functionality has been reimplemented in multiple places in MLIR. Possibly additional copies in downstream projects. Therefore, moving it to a common place.