[llvm-dev] how to prevent LLVM back-end from reordering instructions at instruction scheduling?
Ryan Taylor via llvm-dev
llvm-dev at lists.llvm.org
Tue Nov 15 14:19:26 PST 2016
Krzysztof,
Thanks, I'll look into it.
-Ryan
On Tue, Nov 15, 2016 at 5:18 PM, Krzysztof Parzyszek <
kparzysz at codeaurora.org> wrote:
> You can override TargetInstrInfo::isSchedulingBoundary for that.
>
> -Krzysztof
>
> On 11/15/2016 4:13 PM, Ryan Taylor wrote:
>
>> I have the same issue, would it be easier and more useful to attach a
>> flag to the instruction to tell the scheduler not to move instructions
>> across this boundary?
>>
>> -Ryan
>>
>> On Tue, Nov 15, 2016 at 5:11 PM, Krzysztof Parzyszek via llvm-dev
>> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>>
>> You can create a DAG mutation that adds artificial dependencies
>> between A, B and Z.
>>
>> -Krzysztof
>>
>>
>> On 11/15/2016 3:26 PM, Wei Ding via llvm-dev wrote:
>>
>> Hello,
>>
>> I have a LLVM backend question regarding how to prevent compiler
>> from
>> reordering instructions. For example, I have the following
>> instructions.
>> Z_instruction is the one which I want to insert.
>>
>>
>> // instruction order which I am looking for
>> /////////////////////////////////////////
>> A_instruction
>> B_instruction
>>
>> *Z_instruction*
>>
>> C_instruction
>> D_instruction
>> E_instruction
>> F_instruction
>>
>> *Z_instruction*
>>
>> G_instruction
>> F_instruction
>>
>>
>> ==================================================
>>
>> But I found compiler reordered those instructions like the
>> following.
>> How could I prevent compiler from moving *A_instruction* and
>> *B_instruction* after the first *Z_instruction*? Any
>> recommendations and
>> suggestion are greatly appreciated here!!!
>>
>> *Z_instruction*
>> *
>> *
>> A_instruction
>> B_instruction
>>
>> C_instruction
>> D_instruction
>> E_instruction
>> F_instruction
>>
>> *Z_instruction*
>>
>> G_instruction
>> F_instruction
>>
>> BTW, I have define input/output chain for : *C_instruction,
>> D_instruction, E_instruction, F_instruction and Z_instruction*
>> *
>> *
>> Thank you so much!
>>
>> --
>> Wei Ding
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>>
>>
>> --
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> hosted by The Linux Foundation
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>>
>>
>>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by The Linux Foundation
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20161115/586f97db/attachment.html>
More information about the llvm-dev
mailing list