scf.for

← scf dialect

Bounded counted loop over an index or offset domain with optional loop-carried state.

Operation contract

Property	Value
Semantic phase	source structure
Traits	ImplicitTerminator(scf.yield)
Interfaces	LoopLike

Signature

Kind	Name	Type	Cardinality	Description
Operand	lower_bound	address	required	Inclusive index or physical byte-offset lower bound.
Operand	upper_bound	address	required	Exclusive upper bound in the lower-bound address domain.
Operand	step	address	required	Positive step in the lower-bound address domain.
Operand	iter_args	any	variadic	—
Operand	unroll_factor	index	optional	Optional SSA unroll factor policy consumed by unroll transforms. The factor bounds body cloning and does not require the loop trip count to be static.
Result	results	any	variadic	—
Attribute	unroll_policy	enum ScfForUnrollPolicy	optional	Optional bare unroll policy for required full unroll.
Attribute	unroll_schedule	enum ScfForUnrollSchedule	optional	Optional schedule used when materializing unrolled loop body copies.
Region	body	region	required	Loop body. Terminated by scf.yield. (single block, terminator scf.yield.)

Verification constraints

• SameType(lower_bound, upper_bound, step)
• IterArgsMatchResults(iter_args, results)
• YieldCountMatchesResults(body, results)
• YieldTypesMatchResults(body, results)

Examples

scf.for %iv = [%c0 to %n step %c1] {
  scf.yield
}

scf.for %byte_offset = [%zero to %byte_length step %one] {
  scf.yield
}

%result = scf.for %iv = [%c0 to %n step %c1](%acc = %init : f32) -> (f32) {
  %next = scalar.addf %acc, %acc : f32
  scf.yield %next : f32
}

scf.for %iv = [%c0 to %n step %c1] unroll(%factor) {
  scf.yield
}

scf.for %iv = [%c0 to %n step %c1] unroll(%factor) schedule(interleaved) {
  scf.yield
}

%result = scf.for %iv = [%c0 to %n step %c1](%acc = %init : f32) -> (f32) unroll(%factor) schedule(recurrence) {
  %next = scalar.addf %acc, %acc : f32
  scf.yield %next : f32
}