llvm dev - Oct 2015 - Is there a way to determine what CPU resource is used by which instruction?

I'm trying to figure out if there is a way to figure out what processor
resource is used by which instruction during scheduling. This is purely for
debugging purposes. Since I'm somewhat new to LLVM it is a bit difficult
for me to figure this out.

Initial idea was to insert comments in the generated assembly which would
tell me what what resource is used. MachineInstr has a  uint8_t
AsmPrinterFlags, which I want to use to pass information from the scheduler
to AsmPrinter about which resource is used. I've asked on the IRC channel
how to do it but nobody seems to know. A scheduling debug log was also
mentioned (supposedly it should provide me with the same information) but I
don't know how to generate one.

I'd appreciate any help on the issue.
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Dear Rail,

Can you clarify what you mean by "processor resource?"  Are you
talking
about architecture-visible state (like registers) or micro-architecture 
state (like ALUs) that are typically not visible at the ISA-level?

Regards,

John Criswell

On 10/19/15 2:58 PM, Rail Shafigulin via llvm-dev wrote:
> I'm trying to figure out if there is a way to figure out what 
> processor resource is used by which instruction during scheduling. 
> This is purely for debugging purposes. Since I'm somewhat new to LLVM 
> it is a bit difficult for me to figure this out.
>
> Initial idea was to insert comments in the generated assembly which 
> would tell me what what resource is used. MachineInstr has a  uint8_t 
> AsmPrinterFlags, which I want to use to pass information from the 
> scheduler to AsmPrinter about which resource is used. I've asked on 
> the IRC channel how to do it but nobody seems to know. A scheduling 
> debug log was also mentioned (supposedly it should provide me with the 
> same information) but I don't know how to generate one.
>
> I'd appreciate any help on the issue.
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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On Mon, Oct 19, 2015 at 1:07 PM, John Criswell <jtcriswel at gmail.com>
wrote:
> Dear Rail,
>
> Can you clarify what you mean by "processor resource?"  Are you
talking
> about architecture-visible state (like registers) or micro-architecture
> state (like ALUs) that are typically not visible at the ISA-level?
>
> Regards,
>
> John Criswell
>
John,

Thanks for the reply. I'm talking about micro-architecture state, i.e.
number of ALUs currently available (i.e. that are not preforming any
computation at the moment), number of Load and Store units, number of
floating point multiply and divide units etc.

I would greatly appreciate any help on this.

Thanks
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> On Oct 19, 2015, at 11:58 AM, Rail Shafigulin via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> I'm trying to figure out if there is a way to figure out what processor
resource is used by which instruction during scheduling. This is purely for
debugging purposes. Since I'm somewhat new to LLVM it is a bit difficult for
me to figure this out.
> 
> Initial idea was to insert comments in the generated assembly which would
tell me what what resource is used. MachineInstr has a  uint8_t AsmPrinterFlags,
which I want to use to pass information from the scheduler to AsmPrinter about
which resource is used. I've asked on the IRC channel how to do it but
nobody seems to know. A scheduling debug log was also mentioned (supposedly it
should provide me with the same information) but I don't know how to
generate one.
Look for a #define like this in the llvm CodeGen files:
#define DEBUG_TYPE “misched"

This allows you to use
llc -debug-only=misched
or
clang -mllvm -ldebug-only=misched

to enable the debugging output for that file/topic. You may use the flag
multiple times to enable multiple debugging outputs.

- Matthias

>
> Look for a #define like this in the llvm CodeGen files:
> #define DEBUG_TYPE “misched"
>
> This allows you to use
> llc -debug-only=misched
> or
> clang -mllvm -ldebug-only=misched
>
> to enable the debugging output for that file/topic. You may use the flag
> multiple times to enable multiple debugging outputs.
>
> - Matthias

Mathias,

Thanks. I think this is what I was looking for.
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