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Frédéric Desbiens
a8aebc5206
Two unrelated Cortex-M0 gaps, both left over from earlier work. The memory barriers from #523 reached the Cortex-M0 gnu port but not its ac6 or iar siblings, in either the inline system return in tx_port.h or the assembly routine. Both take the same GNU or IAR code path, and iar already carried the entry barrier, so the missing pieces were the entry pair for ac6 and the barrier after restoring the interrupt posture for both. All three tools now match. The Cortex-M0 example could not link with any toolchain. cortexm0_crt0.S references 23 linker script symbols and the script defined only 12 of them, so __text_start__, __text_end__, __text_load_start__, the rodata and fast section symbols, and the ctors and dtors load addresses were all unresolved. The Cortex-M4 script defines all 23, including a .fast section with no content whose symbols exist so that the startup copy is a no-op, and its comment says as much. The Cortex-M0 script is brought to that same shape. That left the example failing under LLVM only, on instructions that ARMv6-M can encode just one way. The file declared .code 16 but no syntax mode, so GNU as used the legacy divided syntax in which a plain add or sub sets the flags implicitly, while LLVM implements unified syntax only and rejected the non-flag-setting spelling. Declaring .syntax unified and writing movs, adds and subs makes both assemblers agree, and the encodings GNU produces are byte identical before and after, verified by disassembling both objects. The Cortex-M0 example now links with GNU at 22,520 bytes of text and with Arm Toolchain for Embedded at 22,866, so it comes off the list of examples not expected to link and scripts/check_clang.sh now links eight of eight. Assisted-by: Claude Code (Opus 5) <noreply@anthropic.com>