Method ForN

core/codegen/builder.go:225–257

ForN builds a logic block with the following psuedocode: for it := 0; it < n; it++ { cont := cb() if cont == false { break; } } If cb returns nil then the loop will never exit early.

(n *Value, cb func(iterator *Value) (cont *Value))

//
// If cb returns nil then the loop will never exit early.
func (b *Builder) ForN(n *Value, cb func(iterator *Value) (cont *Value)) {
	one := llvm.ConstInt(n.Type().llvmTy(), 1, false)
	zero := b.Zero(n.Type())
	iterator := b.LocalInit("loop_iterator", zero)

	test := b.m.ctx.AddBasicBlock(b.function.llvm, "for_n_test")
	loop := b.m.ctx.AddBasicBlock(b.function.llvm, "for_n_loop")
	exit := b.m.ctx.AddBasicBlock(b.function.llvm, "for_n_exit")

	b.llvm.CreateBr(test)

	b.block(test, llvm.BasicBlock{}, func() {
		done := b.llvm.CreateICmp(llvm.IntSLT, iterator.Load().llvm, n.llvm, "for_n_condition")
		b.llvm.CreateCondBr(done, loop, exit)
	})

	b.block(loop, llvm.BasicBlock{}, func() {
		it := iterator.Load()
		cont := cb(it)
		if b.IsBlockTerminated() {
			return
		}
		b.llvm.CreateStore(b.llvm.CreateAdd(it.llvm, one, "for_n_iterator_inc"), iterator.llvm)
		if cont == nil {
			b.llvm.CreateBr(test)
		} else {
			assertTypesEqual(cont.ty, b.m.Types.Bool)
			b.llvm.CreateCondBr(cont.llvm, test, exit)
		}
	})

	b.setInsertPointAtEnd(exit)
}

// SwitchCase is a single condition and block used as a case statement in a
// switch.