view.atomic.cmpxchg

← view dialect

Atomically compare the bits of one scalar view element with an expected payload, write a replacement payload when they match, and return the old observed payload. Comparison is bitwise for every accepted element type.

Operation contract

Property	Value
Semantic phase	executable
Target contracts	memory.atomic
Interfaces	MemoryAccess
Memory effects	readwrite view

Signature

Kind	Name	Type	Cardinality	Description
Operand	expected	scalar	required	Scalar value compared against memory.
Operand	replacement	scalar	required	Scalar value written on success.
Operand	view	view	required	Typed destination view.
Operand	indices	index	variadic	Dynamic logical element indices.
Result	old	scalar	required	Old memory value observed by the atomic operation.
Attribute	success_ordering	enum AtomicOrdering	required	Memory ordering used when the compare-exchange succeeds.
Attribute	failure_ordering	enum AtomicOrdering	required	Memory ordering used when the compare-exchange fails.
Attribute	scope	enum AtomicScope	required	Required atomic synchronization scope.
Attribute	cache_scope	enum CacheScope	optional	Optional cache/coherency scope required by target lowering.
Attribute	cache_temporal	enum CacheTemporal	optional	Optional temporal cache policy required by target lowering.
Attribute	static_indices	i64_array	required	Static logical element indices with INT64_MIN sentinels for dynamics.

Verification constraints

• HasBitwiseScalar(expected)
• SameElementType(expected, replacement, view, old)
• SameType(expected, replacement, old)

Examples

%old = view.atomic.cmpxchg %expected, %replacement, %view[%row, %col] {success_ordering = acq_rel, failure_ordering = acquire, scope = workgroup} : i32, view<[%M]x[%N]xi32, %layout> -> i32