I'm trying to create a template that emits a single line of ARM assembly with
two register args and two immediate args. The asm statement's triple-quotes was
causing a problem when the template expanded its arguments, so I put the asm
statement in a proc and call that proc from the template. Here's my best
attempt so far:
{.push stackTrace:off.}
proc setField[T](
regVal: T, bitOffset: static int, bitWidth: static int, fieldVal:
RegisterVal
): T {.asmNoStackFrame.} =
asm """
BFI `regVal`, `fieldVal`, #bitOffset, #bitWidth
"""
{.pop.}
# chained field modify
template GPIOAEN*(regVal: RCC_AHB1ENR_Val, fieldVal: uint32):
RCC_AHB1ENR_Val =
setField[RCC_AHB1ENR_Val](regVal, 0, 1, fieldVal)
Run
This results in the following error:
/var/folders/_8/x78bn0wj3nz4gwnbtm47qsqw0000gn/T//ccBPqMCO.s: Assembler
messages:
/var/folders/_8/x78bn0wj3nz4gwnbtm47qsqw0000gn/T//ccBPqMCO.s:93: Error: ARM
register expected -- `bfi regVal_p0,fieldVal_p3,#bitOffset,#bitWidth'
Error: execution of an external compiler program 'arm-none-eabi-gcc -c -w
-fmax-errors=4 -mthumb -march=armv7 -mtune=cortex-m4
-I/opt/homebrew/Cellar/nim/2.0.0_1/nim/lib -I/Users/hidepath/code/nim/arm/src
-o /Users/hidepath/code/nim/arm/build/nimcache/@mmain_7.nim.c.o
/Users/dwhall/GoogleDrive/code/nim/arm/build/nimcache/@mmain_7.nim.c' failed
with exit code: 1
Run
Does anyone know a way to make this work? Even if I get past the
argument-to-register error (above), I don't see how I'll ever get the
argument-to-immediate-value conversion. I have read about, but never coded
macros; do they hold any hope of resolving this?
If you want to play with it, see main_7.nim in:
<https://github.com/dwhall/arm_sandbox> and use `nimble cross` to cross-compile
with your local arm-none-eabi-gcc toolchain. The project may have MacOS and
VSCode assumptions.
