[llvm-dev] Preparing BOLT for LLVM monorepo

Mon Jan 10 13:12:01 PST 2022

Hi Shengchen,

Thank you for the code review and your suggestions!
We've addressed some of them (see inline) but still in the process of
addressing them all.

On Tue, Jan 4, 2022 at 7:56 PM Kan, Shengchen <shengchen.kan at intel.com>
wrote:

> Hi Amir
>
>
>
> I read the MC-related code and it looks fine to me in general. I’m also
> supportive for the merge. The following are some suggestions.
>
>
>
>    1. https://llvm.org/docs/CodingStandards.html#braced-initializer-lists
>     If you use a braced initializer list when initializing a variable, use an
>    equals before the open curly brace. e.g BinaryBasicBlock.h
>
> Addressed, soon to be published.

>
>    1.
>    https://llvm.org/docs/ProgrammersManual.html#fine-grained-debug-info-with-debug-type-and-the-debug-only-option
>    DEBUG_TYPE should not be target specific,
>
> e.g, the definition of DEBUG_TYPE should be same in X86MCPlusBuilder.cpp
> and AArch64MCPlusBuilder.cpp
>
Addressed in
https://github.com/facebookincubator/BOLT/commit/7ca0c5a26714754ec1dd72576ddecaa8b459842c

>
>    1. Functions getShortArithOpcode, getShortBranchOpcode in
>    X86MCPlusBuilder.cpp use reversed mappings as functions
>    getRelaxedOpcodeBranch, getRelaxedOpcodeArith in X86AsmBackend.cpp. Writing
>    twice in two places makes the code difficult to maintain, could we generate
>    the table with tablgen? The memory folding and unfolding tables in
>    X86InstrFoldTables.cpp give an example.
>
> To make sure I get it right: the tables in X86InstrFoldTables.cpp were
generated with tablegen at some point, but are checked in as source code?
Is there a way to rebuild these tables, so I can use that as an example?

>    1. It would better if functions isADD, isAND, isCMP, isDEC, isINC,
>    isSUB and isTEST can be generated with tablgen.
>
> Removed our definitions of isINC/isDEC:
https://github.com/facebookincubator/BOLT/commit/9fec2d58964d643a7436ba2804f8fb967f23881e
How do we approach generating isADD/... with tablegen? There are
appropriate definitions (`defm ADD`, etc)
in llvm/lib/Target/X86/X86InstrArithmetic.td but I'm not sure how to get
tablegen to generate the tables.

Thanks,
-Amir

>
> Best
>
> Shengchen
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *Wang,
> Phoebe via llvm-dev
> *Sent:* Thursday, December 30, 2021 5:33 PM
> *To:* Amir Aupov <amir.aupov at gmail.com>
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] Preparing BOLT for LLVM monorepo
>
>
>
> Hi Amir,
>
>
>
> Amazing job! Thanks for the quick and perfect changes. I don’t have any
> other problems now. Hoping seeing the code in main trunk soon.
>
>
>
> Thanks
>
> Phoebe
>
>
>
> *From:* Amir Aupov <amir.aupov at gmail.com>
> *Sent:* Thursday, December 30, 2021 4:32 PM
> *To:* Wang, Phoebe <phoebe.wang at intel.com>
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] Preparing BOLT for LLVM monorepo
>
>
>
> Hi Phoebe,
>
>
>
> Thank you again for reviewing the codebase and for your feedback. We've
> addressed it in recent commits:
>
> >  1.  Use the monorepo of LLVM in the example for convenience in https://github.com/facebookincubator/BOLT/blob/main/bolt/docs/OptimizingClang.md#getting-clang-7-sources
>
> E.g, git clone --branch=release/7.x https://github.com/llvm/llvm-project.git
>
> https://github.com/facebookincubator/BOLT/commit/c4ed6a11eb264660f5cfe7f5165df35b63d52608
>
>
>
> >  1.  I found there are 142 code with “not implemented”, most of which are in Core/MCPlusBuilder.h.
>
>      *   Do they affect the functionality of BOLT?
>
>      *   Do you have plan to implement them recently or can they be removed instead?
>
> Explained above.
>
> >  2.  I noticed some inconsistent use of braces in the code. Maybe better to follow with LLVM coding standard<https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements>.
>
>      *   https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/BinaryBasicBlock.cpp#L241, L289<https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/BinaryBasicBlock.cpp#L289>, etc.
>
>      *   https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/DebugData.cpp#L193
>
> https://github.com/facebookincubator/BOLT/commit/fe3fcf094e320af4da4a98a5387820cd0ca826b9
>
> https://github.com/facebookincubator/BOLT/commit/b40699ed90882465e49ec46e4d3ad28623e54c69
>
> https://github.com/facebookincubator/BOLT/commit/c21ee425083276a7af700e232df15e2a3d31dacb
>
> https://github.com/facebookincubator/BOLT/commit/ebc06afcfc35fbb4360b3788adeb6228c27ad830
>
> https://github.com/facebookincubator/BOLT/commit/dca3003fce711daee387bbbf66bf4ecbe1b9ab9b
>
> https://github.com/facebookincubator/BOLT/commit/cd526a4550455b0f203771088cef6e512b0dd1a2
>
> >  3.  Some files don’t have a descriptions in the first line, e.g.  DynoStats.cpp<https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/DynoStats.cpp#L1>, ParallelUtilities.cpp<https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/ParallelUtilities.cpp#L1>, etc.
>
> >  4.  Leaving without descriptions might be fine, but the format should be consistent. Leaving with spaces like in BinaryFunctionProfile.cpp<https://github.com/facebookincubator/BOLT/blob/main/bolt/lib/Core/BinaryFunctionProfile.cpp#L1> doesn’t make sense.
>
>
> https://github.com/facebookincubator/BOLT/commit/349c8abc696919e989418895f4ade24a4c910617
>
>
>
> On Tue, Dec 21, 2021 at 4:22 AM Wang, Phoebe <phoebe.wang at intel.com>
> wrote:
>
> Hi Amir,
>
>
>
> It makes sense to me. Thanks!
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *Amir
> Aupov via llvm-dev
> *Sent:* Tuesday, December 21, 2021 8:57 AM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] Preparing BOLT for LLVM monorepo
>
>
>
> Hi Phoebe,
>
>
>
> Thanks again for taking the time to look at the codebase. We've added your
> feedback to our upstreaming tracking issue on github:
> https://github.com/facebookincubator/BOLT/issues/248. We've started
> addressing the issues.
>
>
>
> Regarding "not implemented” in Core/MCPlusBuilder.h: it's a design
> decision to prevent the use of non-implemented target-specific methods
> (these are virtual methods). Target-specific implementation goes to
> X86MCPlusBuilder and AArch64MCPlusBuilder. Some methods only make sense for
> specific targets, so we intend to keep llvm_unreachable statements in
> MCPlusBuilder.h.
>
>
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