llvm dev - Nov 2015 - Hexagon and choosing of slots

> On Hexagon, the slot assignment is determined by the layout of the
> instructions in memory.  The order of the instructions in the packet does
> not matter either in the IR, nor in the .s file, but it does when the
> packet is encoded into the actual machine code.  In LLVM, the Hexagon
> shuffler orders the instructions just prior to encoding.
>
> Specifically, the instructions in the packet are encoded "in
reverse",
> i.e. the instruction that will go to the highest slot will be encoded
> first, then the instruction that will go to the second highest slot, etc.
> In case of a packet with 4 instructions, it will be
>   addr:    slot3
>   addr+4:  slot2
>   addr+8:  slot1
>   addr+12: slot0
> Not all slots have to be occupied. If they are not, the hardware will
> assign the slots based on the instruction, but within a packet the slots
> must be in a decreasing order.  For example:
>   addr:    slot2
>   addr+4:  slot0
> is ok, but
>   addr:    slot1
>   addr+4:  slot0
> is not.
>
> There are also bits in each encoding word that indicate the end of the
> packet: those must also be set properly by the compiler.
>
> -Krzysztof
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by The Linux Foundation
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>
Would you mind pointing me to the source code where actual shuffling
occurs. I looked through lib/Target/Hexagon but was not able to find it. Is
shuffling now part of a core code?

Thanks,

-- 
R
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On 11/24/2015 2:06 PM, Rail Shafigulin wrote:
>
> Would you mind pointing me to the source code where actual shuffling
> occurs. I looked through lib/Target/Hexagon but was not able to find it.
> Is shuffling now part of a core code?
The actual slot assignment is implemented here:
lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.cpp

Here is a wrapper class used in MC:
lib/Target/Hexagon/MCTargetDesc/HexagonMCShuffler.cpp

-Krzysztof

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation

On Tue, Nov 24, 2015 at 12:16 PM, Krzysztof Parzyszek <
kparzysz at codeaurora.org> wrote:
> On 11/24/2015 2:06 PM, Rail Shafigulin wrote:
>
>>
>> Would you mind pointing me to the source code where actual shuffling
>> occurs. I looked through lib/Target/Hexagon but was not able to find
it.
>> Is shuffling now part of a core code?
>>
>
> The actual slot assignment is implemented here:
> lib/Target/Hexagon/MCTargetDesc/HexagonShuffler.cpp
>
> Here is a wrapper class used in MC:
> lib/Target/Hexagon/MCTargetDesc/HexagonMCShuffler.cpp
>
>
> -Krzysztof
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by The Linux Foundation
>
Thanks!!! I also know why I wasn't able to find the shuffler. I'm
working
with LLVM 3.5 (at the moment I'm locked into it) and Hexagon target
doesn't
have the shuffler in it.

-- 
R
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