Re: [Patch, ARM, GAS] Fix single-reg LDM/STM to LDR/STR translation.

[Richard Earnshaw <rearnsha at arm dot com>]

On Fri, 2010-09-17 at 11:06 +0100, Tejas Belagod wrote:
> Hi,
> 
> The attached patch fixes the translation of single-register LDM/STM. For
> instruction like:
>         STMIA sp, {r1}
> this patch chooses to encode this as 
>         STR r1, [sp, #0]
> which can fit into a 16-bit thumb encoding. This is in line with what
> the ARM ARM has to say about choosing encodings for STM:
> 
> "Encoding T2 does not support a list containing only one register. If an
> STM instruction with just one register <Rt> in the list is assembled to
> Thumb and encoding T1 is not available, it is assembled to the
> equivalent STR<c><q> <Rt>,[<Rn>]{,#4} instruction"
> 
> For LDM/STM with single-register list that can't fit into 16-bit
> encoding after translation to STR/LDR, 32-bit encoding is used. Care
> also has been taken to record UNPREDICTABLE errors where necessary. 
> 
> Tested with arm-none-eabi. OK?
> 
> --
> Tejas Belagod
> ARM.
> 
> Changelog:
> 
> gas/
> 
> 2010-09-17  Tejas Belagod  <tejas.belagod@arm.com>
> 
> 	* config/tc-arm.c (do_t_ldmstm): Add logic to handle
> 	single-register list for ldm/stm.
> 
> gas/testsuite
> 
> 2010-09-17  Tejas Belagod  <tejas.belagod@arm.com>
> 
> 	* gas/arm/thumb2_ldmstm.d: Change single-register stmia to use 
> 	16-bit str encoding instead of str.w. Likewise for ldmia.
> 	* gas/arm/thumb2_ldmstm.s: Change stmia comment. Add tests for
> 	T1 ldmia-to-ldr.

This is OK.

R.