Re: Emission of store_multiple and load_multiple patterns

[noeljohn <noel dot daniel at gmx dot com>]

Ian Lance Taylor-3 wrote:
> 
> noeljohn <noel.daniel@gmx.com> writes:
> 
>> Ian Lance Taylor-3 wrote:
>>> 
>>> noeljohn <noel.daniel@gmx.com> writes:
>>> 
>>>>         I am working on a new risc machine. I have defined the
>>>> "store_multiple" and "load_multiple" pattern and the system builds
>>>> fine.
>>>> But
>>>> when I compile the C program for a declared integer array, the
>>>> "store_multiple" and "load_multiple" patterns are not getting emitted.
>>>> Instead simple load and store patterns are emitted multiple times. As
>>>> per
>>>> actual working store_multiple and load_multiple patters need to get
>>>> emitted.
>>> 
>>> What do your store_multiple and load_multiple insns look like?
>>> 
>>> E.g., if they only work for consecutive registers, then gcc can only
>>> match them after register allocation, but there is no appropriate
>>> optimization pass to do so.  In that case you are going to have write
>>> peepholes for them, and you're going to have to generate them
>>> explicitly in your backend's prologue and epilogue generation.
>>> 
>>> 
>>> Ian
>>> 
>>> 
>>
>>
>> Thank you for replying.
>> According to my understanding, it works for consecutive registers as I am
>> just declaring an array in my test case. To be specific, how do I get
>> "rodata" section in assembly generated that contains only the
>> data(integers)
>> in the array declared,, because when I compile with other already build
>> processors, it creates this rodata section and then using a single
>> instruction stores all the elements of array in memory. 
> 
> 
> It's difficult to say how this works without more information.  Is the
> array being treated as a vector?
> 
> It's easy enough to get an rodata section in your assembly code, that
> should happen more or less automatically if you write
>     const int ai[] = { 1, 2, 3, 4 };
> I don't know how to load that using a load-multiple instruction unless
> it is being treated as a vector.
> 
> Ian
> 
> 

Hello Sir,
  The array as I have seen is not being treated as a vector. What it does is
it directly loads the integer array data into the stack. This is normally
done for processors which does not have a support for multiple loading and
storing of words. 

noeljohn
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