[jogibear9988]

The global try-expression count forces extra left-value spills even when the right operand can only load an atomic value and cannot enter a protected region.

Keep that value on the stack for parameter/constant/default RHS operands and retain spills for complex or opaque intrinsic operands.

Right operands observing mutations made by a completed finalizer, parameter/constant/default variants, and an intrinsic LightExpression constant that emits an exception region.

Validation: Release solution build; full Standard and LightExpression runners on .NET 8, .NET 10 and .NET Framework. net8.0: 562 TestX cases and 1744 legacy cases; net10.0: 562 TestX cases and 1745 legacy cases; net472: 543 TestX cases and 1610 legacy cases.

Shared-workload measurements

Base: bac81d0734c0 (master); patch: 019767854711. Windows ARM64, SDK 10.0.301; .NET 8.0.28 and 10.0.9. Expression trees and invocation adapters are prepared outside the timed loops. Strict FEC compilation, tiered compilation disabled, one pinned logical processor, two opposite-load-order processes per runtime, seven alternating paired samples per process, 30 ms calibration target; medians of 14 samples.

Both columns below are FEC. “System trees” names the expression API, not the System compiler. Compilation includes delegate creation; invocation measures the returned delegate through the same adapter on each side. Managed allocations use GC.GetAllocatedBytesForCurrentThread.

Runtime / FEC API	Workload	Compile μs, master → patch	Compile B/op, master → patch	Invoke ns, master → patch	Invoke B/op, master → patch
net10.0 / LightExpression	arithmetic_after_try	6.580 → 6.454	1472.07	3.294 → 3.298	0.00
net10.0 / LightExpression	ref_compound	4.802 → 5.418	880.06	3.354 → 4.005	0.00
net10.0 / LightExpression	scalar_add	5.487 → 5.283	872.06	3.252 → 3.208	0.00
net10.0 / LightExpression	try_finally	5.605 → 6.586	1472.00	3.691 → 3.244	0.00
net10.0 / System trees	arithmetic_after_try	7.756 → 6.772	1472.08	3.256 → 3.194	0.00
net10.0 / System trees	ref_compound	6.257 → 6.695	880.29	3.401 → 3.488	0.00
net10.0 / System trees	scalar_add	5.036 → 4.945	872.07	3.003 → 2.927	0.00
net10.0 / System trees	try_finally	5.248 → 5.824	1472.00	3.220 → 2.928	0.00
net8.0 / LightExpression	arithmetic_after_try	2.048 → 1.883	1472.02	2.671 → 2.592	0.00
net8.0 / LightExpression	ref_compound	1.757 → 1.796	880.02	2.322 → 2.355	0.00
net8.0 / LightExpression	scalar_add	1.529 → 1.537	872.02	2.307 → 2.303	0.00
net8.0 / LightExpression	try_finally	1.708 → 1.625	1472.00	2.397 → 2.377	0.00
net8.0 / System trees	arithmetic_after_try	2.819 → 2.577	1472.03	2.505 → 2.507	0.00
net8.0 / System trees	ref_compound	2.282 → 2.286	880.12	2.366 → 2.395	0.00
net8.0 / System trees	scalar_add	2.106 → 2.186	872.04	2.455 → 2.375	0.00
net8.0 / System trees	try_finally	2.310 → 2.209	1472.00	2.371 → 2.303	0.00

Emitted IL matched byte-for-byte for 12/16 shared control delegates. Observed compilation changes range from -12.7% to +17.5%; invocation changes from -12.1% to +19.4%. Slower results are retained. Even identical-IL controls vary, so these short machine timings do not establish a blanket runtime speedup or absence of regressions.
Managed allocations were unchanged on every shared workload in this run.

Longer confirmation run

Same base, patch and paired protocol, with a 150 ms calibration target instead of 30 ms. These results are additional measurements of the same code; they do not replace slower observations above.

Runtime / FEC API	Workload	Compile μs, master → patch	Compile B/op	Invoke ns, master → patch	Invoke B/op
net10.0 / LightExpression	arithmetic_after_try	5.392 → 4.768	1472.01	2.837 → 2.878	0.00
net10.0 / LightExpression	ref_compound	4.433 → 4.260	880.01	3.338 → 3.481	0.00
net10.0 / LightExpression	scalar_add	3.926 → 3.860	872.01	3.214 → 3.170	0.00
net10.0 / LightExpression	try_finally	4.855 → 4.818	1472.00	2.837 → 2.872	0.00
net10.0 / System trees	arithmetic_after_try	6.351 → 6.050	1472.01	2.794 → 2.797	0.00
net10.0 / System trees	ref_compound	5.520 → 5.494	880.06	2.907 → 2.922	0.00
net10.0 / System trees	scalar_add	4.672 → 4.721	872.01	2.817 → 2.864	0.00
net10.0 / System trees	try_finally	5.581 → 5.715	1472.00	3.285 → 3.098	0.00
net8.0 / LightExpression	arithmetic_after_try	5.781 → 5.960	1472.01	3.221 → 3.150	0.00
net8.0 / LightExpression	ref_compound	3.943 → 3.938	880.01	2.826 → 3.021	0.00
net8.0 / LightExpression	scalar_add	4.115 → 4.527	872.01	3.613 → 3.675	0.00
net8.0 / LightExpression	try_finally	5.298 → 5.748	1472.00	3.275 → 3.309	0.00
net8.0 / System trees	arithmetic_after_try	9.214 → 8.968	1472.02	3.650 → 3.234	0.00
net8.0 / System trees	ref_compound	6.078 → 5.555	880.08	3.041 → 2.979	0.00
net8.0 / System trees	scalar_add	4.549 → 4.462	872.02	2.974 → 3.138	0.00
net8.0 / System trees	try_finally	5.339 → 5.409	1472.00	3.270 → 3.107	0.00