[jogibear9988]

A typed label encountered before its backward jumps can lack a result local and return label. Reserve both when emitting the label, so later jumps reuse the same storage and target.

Backward Return, Goto and Break to typed labels, compared with System compilation across compiler flags. Regressions require strict FEC compilation. Native suites cover Standard and LightExpression.

Validation

Local validation uses master baseline 094d067 plus this change. Release solution build: zero warnings/errors.

Runtime	TestX groups	Legacy tests
.NET 10	489 passed	1,756 passed
.NET 8	489 passed	1,755 passed
.NET Framework 4.7.2	468 passed	1,639 passed

Measurements

Master baseline 094d0678 → this change, Release, Windows ARM64, .NET 8.0.28 / 10.0.9. Compilation uses prebuilt trees; runtime measures invocation through the same wrapper. Two fresh process rounds with reversed load order, seven samples per round, about 30 ms calibration, one logical CPU and tiered compilation disabled. Tables use the median of the two per-round medians.

The controls below produce correct results on master for their measured inputs. Newly supported trees have no valid before/after execution comparison because master rejects them, produces incorrect results or emits invalid IL. Timings include machine and JIT/code-placement variation; the unchanged add control helps show that variation. These observations do not prove universal performance neutrality.

net8.0 results (master → change)

API / workload	Compile ns	Invoke ns	Compile B/op	Invoke B/op
Standard / add_control	1504.5 → 1472.1	2.6 → 2.6	872.0 → 872.0	0.0 → 0.0
Standard / forward_label	1849.5 → 1651.2	2.5 → 2.4	1048.0 → 1048.0	0.0 → 0.0
Standard / label_value	1335.8 → 1451.1	2.6 → 2.5	920.0 → 920.0	0.0 → 0.0
Light / add_control	1358.4 → 1313.2	2.5 → 2.4	872.0 → 872.0	0.0 → 0.0
Light / forward_label	1887.5 → 1790.6	2.4 → 2.5	1048.0 → 1048.0	0.0 → 0.0
Light / label_value	1585.9 → 1286.9	2.7 → 2.8	920.0 → 920.0	0.0 → 0.0

net10.0 results (master → change)

API / workload	Compile ns	Invoke ns	Compile B/op	Invoke B/op
Standard / add_control	5856.7 → 5138.5	3.0 → 3.1	872.1 → 872.1	0.0 → 0.0
Standard / forward_label	6350.3 → 6570.4	2.9 → 2.7	1048.1 → 1048.1	0.0 → 0.0
Standard / label_value	3946.6 → 4235.6	2.5 → 2.6	920.0 → 920.0	0.0 → 0.0
Light / add_control	4610.3 → 4697.8	2.8 → 2.9	872.1 → 872.1	0.0 → 0.0
Light / forward_label	4426.6 → 5423.8	3.1 → 3.1	1048.0 → 1048.0	0.0 → 0.0
Light / label_value	2556.8 → 2546.0	2.7 → 2.7	920.0 → 920.0	0.0 → 0.0

Emitted IL differs in these measured workloads: none.
No measured allocation increase above 0.1 B/op in these controls.