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Revert "[MLIR][Transforms] Fix Mem2Reg removal order to respect dominance (#68687)" #68732

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Merged
merged 1 commit into from
Oct 10, 2023
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Revert "[MLIR][Transforms] Fix Mem2Reg removal order to respect dominance (#68687)" #68732

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28 changes: 12 additions & 16 deletions mlir/lib/Transforms/Mem2Reg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -96,9 +96,6 @@ using namespace mlir;

namespace {

using BlockingUsesMap =
llvm::MapVector<Operation *, SmallPtrSet<OpOperand *, 4>>;

/// Information computed during promotion analysis used to perform actual
/// promotion.
struct MemorySlotPromotionInfo {
Expand All @@ -109,7 +106,7 @@ struct MemorySlotPromotionInfo {
/// its uses, it is because the defining ops of the blocking uses requested
/// it. The defining ops therefore must also have blocking uses or be the
/// starting point of the bloccking uses.
BlockingUsesMap userToBlockingUses;
DenseMap<Operation *, SmallPtrSet<OpOperand *, 4>> userToBlockingUses;
};

/// Computes information for basic slot promotion. This will check that direct
Expand All @@ -132,7 +129,8 @@ class MemorySlotPromotionAnalyzer {
/// uses (typically, removing its users because it will delete itself to
/// resolve its own blocking uses). This will fail if one of the transitive
/// users cannot remove a requested use, and should prevent promotion.
LogicalResult computeBlockingUses(BlockingUsesMap &userToBlockingUses);
LogicalResult computeBlockingUses(
DenseMap<Operation *, SmallPtrSet<OpOperand *, 4>> &userToBlockingUses);

/// Computes in which blocks the value stored in the slot is actually used,
/// meaning blocks leading to a load. This method uses `definingBlocks`, the
Expand Down Expand Up @@ -235,7 +233,7 @@ Value MemorySlotPromoter::getLazyDefaultValue() {
}

LogicalResult MemorySlotPromotionAnalyzer::computeBlockingUses(
BlockingUsesMap &userToBlockingUses) {
DenseMap<Operation *, SmallPtrSet<OpOperand *, 4>> &userToBlockingUses) {
// The promotion of an operation may require the promotion of further
// operations (typically, removing operations that use an operation that must
// delete itself). We thus need to start from the use of the slot pointer and
Expand All @@ -245,7 +243,7 @@ LogicalResult MemorySlotPromotionAnalyzer::computeBlockingUses(
// use it.
for (OpOperand &use : slot.ptr.getUses()) {
SmallPtrSet<OpOperand *, 4> &blockingUses =
userToBlockingUses[use.getOwner()];
userToBlockingUses.getOrInsertDefault(use.getOwner());
blockingUses.insert(&use);
}

Expand Down Expand Up @@ -283,7 +281,7 @@ LogicalResult MemorySlotPromotionAnalyzer::computeBlockingUses(
assert(llvm::is_contained(user->getResults(), blockingUse->get()));

SmallPtrSetImpl<OpOperand *> &newUserBlockingUseSet =
userToBlockingUses[blockingUse->getOwner()];
userToBlockingUses.getOrInsertDefault(blockingUse->getOwner());
newUserBlockingUseSet.insert(blockingUse);
}
}
Expand Down Expand Up @@ -518,16 +516,14 @@ void MemorySlotPromoter::computeReachingDefInRegion(Region *region,
}

void MemorySlotPromoter::removeBlockingUses() {
llvm::SmallVector<Operation *> usersToRemoveUses(
llvm::make_first_range(info.userToBlockingUses));
// The uses need to be traversed in *reverse dominance* order to ensure that
// transitive replacements are performed correctly.
llvm::sort(usersToRemoveUses, [&](Operation *lhs, Operation *rhs) {
return dominance.properlyDominates(rhs, lhs);
});
llvm::SetVector<Operation *> usersToRemoveUses;
for (auto &user : llvm::make_first_range(info.userToBlockingUses))
usersToRemoveUses.insert(user);
SetVector<Operation *> sortedUsersToRemoveUses =
mlir::topologicalSort(usersToRemoveUses);

llvm::SmallVector<Operation *> toErase;
for (Operation *toPromote : usersToRemoveUses) {
for (Operation *toPromote : llvm::reverse(sortedUsersToRemoveUses)) {
if (auto toPromoteMemOp = dyn_cast<PromotableMemOpInterface>(toPromote)) {
Value reachingDef = reachingDefs.lookup(toPromoteMemOp);
// If no reaching definition is known, this use is outside the reach of
Expand Down
13 changes: 0 additions & 13 deletions mlir/test/Dialect/LLVMIR/mem2reg.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -683,16 +683,3 @@ llvm.func @no_inner_alloca_promotion(%arg: i64) -> i64 {
// CHECK: llvm.return %[[RES]] : i64
llvm.return %2 : i64
}

// -----

// CHECK-LABEL: @transitive_reaching_def
llvm.func @transitive_reaching_def() -> !llvm.ptr {
%0 = llvm.mlir.constant(1 : i32) : i32
// CHECK-NOT: alloca
%1 = llvm.alloca %0 x !llvm.ptr {alignment = 8 : i64} : (i32) -> !llvm.ptr
%2 = llvm.load %1 {alignment = 8 : i64} : !llvm.ptr -> !llvm.ptr
llvm.store %2, %1 {alignment = 8 : i64} : !llvm.ptr, !llvm.ptr
%3 = llvm.load %1 {alignment = 8 : i64} : !llvm.ptr -> !llvm.ptr
llvm.return %3 : !llvm.ptr
}