fix(arm): gale-wasm linkability — internal-call relocations + Thumb BL encoding (#167) + graceful skip (#168)#169
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…coding (#167) Three defects made every synth ARM object with a function call non-linkable (regression from v0.3.0): 1. arm_backend.rs recorded a relocation ONLY for BL labels starting with `__meld_` (import dispatch stubs). Internal calls (`BL func_N`) got no relocation, so they were emitted as bare `bl #0` with nothing to patch them. Now records a relocation for every BL. 2. build_relocatable_elf only defined export-name symbols; the selector emits `BL func_{wasm_index}`, so internal-call relocations had no target symbol. Now defines a `func_{index}` symbol per function (alongside the export name) and emits R_ARM_THM_CALL (Thumb) — not R_ARM_CALL (ARM mode). 3. The Thumb BL placeholder encoded the second halfword as 0xD000, which (J1=J2=0, S=0 ⟹ I1=I2=1) bakes in a bogus ~+0x600000 addend — the source of the garbage `bl c0000c` target AND the linker "relocation truncated to fit". A true zero-offset Thumb BL is 0xF800 (J1=J2=1). Fixed. Verified on the #167 minimal repro (2 internal-call functions): the .o now carries an R_ARM_THM_CALL against func_0, links with arm-none-eabi-ld with zero errors (was "truncated to fit"), and the call resolves to the callee. All 180+ synth-backend tests pass. Remaining (follow-up): standalone --cortex-m direct call resolution; $t mapping symbols for Thumb disassembly/debug display. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
… aborting (#168) A single function that the backend cannot compile (e.g. compiler_builtins::float::div, which exhausts the i64 register-pair allocator) previously aborted the entire --all-exports module compile. For the gale --whole-archive route this means one piece of dead weight kills 190+ otherwise-fine functions. Now compile_all_exports records the failure (with a per-function 'warning: skipping function ...' diagnostic), continues, and reports the full skipped set at the end. A caller that actually references a skipped function gets a clean 'undefined symbol func_N' link error (it becomes an undefined external via the #167 relocation path) — far more actionable than a whole-module failure. If EVERY function is skipped, we still error (nothing to emit). The underlying allocator limitation (no consecutive free pair for i64) is unchanged; this is the graceful-degradation mitigation the issue requested. Spilling / pair-coalescing remains a follow-up. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This was referenced May 29, 2026
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Bumps workspace 0.11.0 → 0.11.1, sweeps the intra-workspace path-dep pins + MODULE.bazel, promotes [Unreleased] → [0.11.1] with the falsification statement. PR #169 (closes #167, #168): internal-call relocations + correct Thumb BL encoding (0xF800) make synth ARM objects with function calls linkable again (v0.3.0 regression); --all-exports skips un-compilable functions instead of aborting. Backend bugfix only — no proof-suite changes.
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Fixes the two serious gale-wasm compilation blockers filed against v0.11.0.
#167 — non-linkable ELF (regression from v0.3.0)
Every synth ARM object containing a function call was non-linkable. Three chained defects:
arm_backend.rsrecorded a relocation only forBLlabels starting with__meld_(import dispatch). InternalBL func_Ngot none → emitted as barebl #0with nothing to patch. → record a relocation for everyBL.build_relocatable_elfdefined only export-name symbols, but the selector emitsBL func_{wasm_index}. → define afunc_{index}symbol per function and emitR_ARM_THM_CALL(Thumb) instead ofR_ARM_CALL(ARM-mode).0xD000— withJ1=J2=0, S=0that decodes toI1=I2=1, baking in a bogus ~+0x600000 addend. That is the original garbagebl c0000ctarget and the linkerrelocation truncated to fit. A true zero-offset Thumb BL is0xF800(J1=J2=1). Fixed.Verified on the issue's minimal 2-function repro: the
.onow carriesR_ARM_THM_CALL → func_0, links witharm-none-eabi-ldwith zero errors (was "truncated to fit"), and the call resolves to the callee.#168 — register exhaustion aborts whole module
compiler_builtins::float::divexhausts the i64 consecutive-pair allocator; under--all-exports(gale's--whole-archive) this killed the entire module. Nowcompile_all_exportsskips the un-compilable function with a diagnostic, continues, and reports the skipped set; a caller that references it gets a cleanundefined symbol func_Nlink error (via the #167 relocation path). Erroring only if every function fails. (The allocator limitation itself — spill / pair-coalescing — remains a follow-up.)Tests
Falsification
This is wrong if: a module with internal calls still produces a
.othat fails to link (noR_ARM_THM_CALLfor the call, or a bogus addend), or--all-exportsstill aborts on a single un-compilable function.Follow-ups (filed-worthy, not blocking)
--cortex-m(non-relocatable) direct call resolution.$t/$amapping symbols (Thumb disassembly/debug display; not required for linking).🤖 Generated with Claude Code