HowlFrame #90 Phase 3b: experimental while bytecode

[howlcipher]

Summary

Experimental -compile-hfir-bc now compiles and runs a tiny while. LowerAST records that loop header's control edges as the condition, then the body. LowerToBytecode follows those edges and emits the existing JUMP_IF_FALSE and JUMP opcodes, with the same relative offsets as the AST bytecode compiler. A while whose control edges are missing or swapped fails closed with HFIR_BYTECODE_UNSUPPORTED and no bytecode program.

Production -compile-bc is still runHFIRGate and then bytecode.CompileToBytecode on the AST. sleep still compiles on that flag and is still rejected by -compile-hfir-bc. This is not a CFG or SSA pass: if, for, and every other node still have empty control edges. No new opcode, no new capability, no Wasm, and no module linker. The model-adapter transport still rejects while, so #88 stays closed. write_file and mkdir stay deferred. #90 stays Partial.

Journal: docs/journals/2026-09-30_lowered_hfir_abi_phase3b_while.md.

How to test

gofmt -l .
go vet ./...
go test ./...

The shared fixture is tests/conformance/abi_v1/10_while.howl (while_control in tests/conformance/lowered_hfir_abi_v1.json). A false loop must not print. A counting loop prints 1, 2, and 3 on the experimental bytecode path, production bytecode, the interpreter, Go, and JavaScript:

go test ./tools/difftest/ -run TestLoweredHFIRABIConformance -count=1

go test ./internal/vm/ -run TestHFIRBytecode -count=1 compares the experimental artifact with AST bytecode on a counting loop, a loop that does not enter, a nested loop, a loop inside defun, and a non-bool condition (TYPE_ERROR, empty stdout).

  

[howlcipher]

Phase 3b looks clean on the fence.

-compile-hfir-bc now runs a tiny while off ControlEdges (condition → body) with the existing JUMP_IF_FALSE / JUMP layout. Prod -compile-bc is still AST after the gate — locked by the sleep split. No new opcode, no new cap, no Wasm, no linker, no #88 reopen. write_file / mkdir stay deferred. #90 stays Partial.

Hard nos look clean. CI build is green on d466ff5e. Good to undraft + squash-merge when you’re ready — leave #90 Partial.