int64_t divide crashing on cortex-m3

drwho drwho@infidigm.net
Wed Sep 21 21:31:00 GMT 2016


On 2016-09-21 12:46 PM, Richard Earnshaw (lists) wrote:
>
> movlt is a conditional instruction matching mov<c> where <c> == lt (less
> than).  The instruction in cortex-m3 is used by prefixing it with an IT
> instruction which modifies the behaviour of subsequent instructions.  So
>
> 	it lt
> 	movlt xxxx
>
> is perfectly legal on this processor.
>
> MOVT is a completely different instruction.  It inserts a 16-bit value
> in the top half of the destination register, overwriting the previous
> bits in that register but leaving the lower half unchanged.
>
> This is all documented in the ARMv7-M version of the ARM ARM
> (registration required).
>
> http://infocenter.arm.com/help/topic/com.arm.doc.ddi0403e.b/index.html
>
>
> R.
I'm not very familiar with conditional instruction matching, so I got 
all excited when I thought I found a missing instruction. Sorry.  Turns 
out I was getting the hard fault because I had not enabled the other 
fault handlers.  The real fault is from a bus error.....Imprecise data 
bus error = "data bus error has occurred, but the return address in the 
stack frame is not related to the instruction that caused the error".

Jon



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