scf.while

← scf dialect

Unbounded loop with explicit before and after regions. The before region terminates with scf.condition, and the after region terminates with scf.yield.

Operation contract

Property	Value
Semantic phase	source structure
Interfaces	LoopLike

Signature

Kind	Name	Type	Cardinality	Description
Operand	iter_args	any	variadic	—
Result	results	any	variadic	—
Region	before	region	required	Runs before each condition check. Terminated by scf.condition. (single block, terminator scf.condition.)
Region	after	region	required	Runs when the condition is true. Terminated by scf.yield. (single block, terminator scf.yield.)

Verification constraints

• IterArgsMatchResults(iter_args, results)
• BlockArgCount(before, iter_args)
• BlockArgsMatchTypes(before, iter_args)
• BlockArgCount(after, iter_args)
• BlockArgsMatchTypes(after, iter_args)
• YieldCountMatchesResults(after, results)
• YieldTypesMatchResults(after, results)

Examples

scf.while {
  scf.condition %cond : i1
} do {
  scf.yield
}

%result = scf.while(%before = %init : index) -> (index) {
  scf.condition %keep_going, %before : i1, index
} do(%body: index) {
  %next = index.add %body, %one : index
  scf.yield %next : index
}