bb5050a50d
I found that .data is not correctly initialized with firmware images
that use over 64kB of flash. The problem is that the data in .data
(which is stored in flash, and copied to RAM at reset) is beyond the
64kB limit and must therefore be loaded using the elpm instruction
instead of the lpm instruction.
I encountered this issue while getting testdata/math.go to work for AVR.
The following command mostly works with this patch, while it prints
garbage withtout it:
tinygo run -target=simavr -size=short -scheduler=none ./testdata/math.go
(This also requires a patch to picolibc to work, see
https://github.com/picolibc/picolibc/pull/371)
It still doesn't work entirely with this patch: some of the math
operations have an incorrect result. But at least it's an improvement as
it won't print garbage anymore.
84 строки
2,2 КиБ
ArmAsm
84 строки
2,2 КиБ
ArmAsm
; This file provides common code across AVRs that cannot be implemented directly
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; in Go.
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; The reset vector is device-specific and is generated by tools/gen-device-avr.py.
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; These definitions are necessary because LLVM does not yet know these register
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; aliases. See: https://reviews.llvm.org/D96492
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#define xl r26
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#define xh r27
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#define yl r28
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#define yh r29
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#define zl r30
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#define zh r31
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; Ugly hack until https://reviews.llvm.org/D137572 is merged.
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#if !defined(__AVR_HAVE_ELPM__) && defined(__flash1)
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#define __AVR_HAVE_ELPM__
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#endif
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; Startup code
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.section .text.__vector_RESET
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.global __vector_RESET
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__vector_RESET:
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clr r1 ; r1 is expected to be 0 by the C calling convention
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; Set up the stack pointer.
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ldi xl, lo8(_stack_top)
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ldi xh, hi8(_stack_top)
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out 0x3d, xl; SPL
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out 0x3e, xh; SPH
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; Subtract one from the stack pointer, so it doesn't point in the .data section.
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push r0
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; Initialize .data
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init_data:
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ldi xl, lo8(_sdata)
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ldi xh, hi8(_sdata)
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ldi yl, lo8(_edata)
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ldi yh, hi8(_edata)
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ldi zl, lo8(_sidata)
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ldi zh, hi8(_sidata)
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#ifdef __AVR_HAVE_ELPM__
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ldi r16, hh8(_sidata) ; RAMPZ = hh8(_sidata)
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out 0x3b, r16
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#endif
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init_data_loop:
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cp xl, yl ; if x == y
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cpc xh, yh
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breq init_data_end ; goto main
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#ifdef __AVR_HAVE_ELPM__
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elpm r0, Z+ ; r0 = *(z++)
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#else
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lpm r0, Z+ ; r0 = *(z++)
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#endif
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st X+, r0 ; *(x++) = r0
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rjmp init_data_loop ; goto init_data_loop
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init_data_end:
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; main will be placed right after here by the linker script so there's no
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; need to jump.
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; The only thing this WDT handler really does is disable itself, to get out of
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; sleep mode.
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.section .text.__vector_WDT
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.global __vector_WDT
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__vector_WDT:
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push r16
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clr r16
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wdr ; Reset watchdog
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out 0x34, r16 ; Clear reset reason (MCUSR)
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; part 1: set WDCE and WDE to enable editing WDTCSR
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lds r16, 0x60 ; r16 = WDTCSR
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ori r16, 0x18 ; r16 |= WDCE | WDE
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sts 0x60, r16 ; WDTCSR = r16
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; part 2: within 4 clock cycles, set the new value for WDTCSR
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clr r16
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sts 0x60, r16 ; WDTCSR = 0
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pop r16
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reti
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