Am 29.03.20 um 22:46 schrieb Christo Crause via fpc-devel:
According to the Xtensa ISA 4.3.8 the SEXT instruction is optional (and
some others too) and apparently not implemented for ESP8266 according to
core-isa.h in ESP8266_RTOS_SDK
(https://github.com/espressif/ESP8266_RTOS_SDK/blob/master/components/esp8266/include/xtensa/config/core-isa.h).
This explains why xtensa-lx106-elf-as does not recognise the SEXT
instruction.
It seems that a different instruction sequence should be used for sign
extension for the lx106 subarch.
Ok, I see. Let me first integrate everything done so far in trunk, then
we can continue with the details :)
Also core-isa.h indicates XCHAL_HAVE_WINDOWED = 0, which I take to mean
that the LX106 toolchain doesn't know/implement the windowed ABI, which
explains why setting the FPC ABI to windowed caused as to flag retw as
unknown.
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