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Attributor: Propagate align to atomicrmw instructions #134837

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Merged
merged 1 commit into from
Apr 8, 2025
Merged

Attributor: Propagate align to atomicrmw instructions #134837

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20 changes: 15 additions & 5 deletions llvm/lib/Transforms/IPO/AttributorAttributes.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5283,7 +5283,7 @@ struct AAAlignImpl : AAAlign {

/// See AbstractAttribute::manifest(...).
ChangeStatus manifest(Attributor &A) override {
ChangeStatus LoadStoreChanged = ChangeStatus::UNCHANGED;
ChangeStatus InstrChanged = ChangeStatus::UNCHANGED;

// Check for users that allow alignment annotations.
Value &AssociatedValue = getAssociatedValue();
Expand All @@ -5297,16 +5297,26 @@ struct AAAlignImpl : AAAlign {
STATS_DECLTRACK(AAAlign, Store,
"Number of times alignment added to a store");
SI->setAlignment(getAssumedAlign());
LoadStoreChanged = ChangeStatus::CHANGED;
InstrChanged = ChangeStatus::CHANGED;
}
} else if (auto *LI = dyn_cast<LoadInst>(U.getUser())) {
if (LI->getPointerOperand() == &AssociatedValue)
if (LI->getAlign() < getAssumedAlign()) {
LI->setAlignment(getAssumedAlign());
STATS_DECLTRACK(AAAlign, Load,
"Number of times alignment added to a load");
LoadStoreChanged = ChangeStatus::CHANGED;
InstrChanged = ChangeStatus::CHANGED;
}
} else if (auto *RMW = dyn_cast<AtomicRMWInst>(U.getUser())) {
if (RMW->getPointerOperand() == &AssociatedValue) {
if (RMW->getAlign() < getAssumedAlign()) {
STATS_DECLTRACK(AAAlign, AtomicRMW,
"Number of times alignment added to atomicrmw");

RMW->setAlignment(getAssumedAlign());
InstrChanged = ChangeStatus::CHANGED;
}
}
}
}

Expand All @@ -5315,8 +5325,8 @@ struct AAAlignImpl : AAAlign {
Align InheritAlign =
getAssociatedValue().getPointerAlignment(A.getDataLayout());
if (InheritAlign >= getAssumedAlign())
return LoadStoreChanged;
return Changed | LoadStoreChanged;
return InstrChanged;
return Changed | InstrChanged;
}

// TODO: Provide a helper to determine the implied ABI alignment and check in
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/Attributor/align-atomic.ll
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Expand Up @@ -16,7 +16,7 @@ define i32 @atomicrmw_add_no_op(ptr align 4 %ptr, i32 %val) {
define i32 @atomicrmw_add_propagate(ptr align 8 %ptr, i32 %val) {
; CHECK-LABEL: define i32 @atomicrmw_add_propagate(
; CHECK-SAME: ptr nofree noundef nonnull align 8 captures(none) dereferenceable(4) [[PTR:%.*]], i32 [[VAL:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[RESULT:%.*]] = atomicrmw add ptr [[PTR]], i32 [[VAL]] seq_cst, align 2
; CHECK-NEXT: [[RESULT:%.*]] = atomicrmw add ptr [[PTR]], i32 [[VAL]] seq_cst, align 8
; CHECK-NEXT: ret i32 [[RESULT]]
;
%result = atomicrmw add ptr %ptr, i32 %val seq_cst, align 2
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