[llvm-dev] Preparing BOLT for LLVM monorepo

Tue Jan 4 19:56:24 PST 2022

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
  2.  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

  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.
  2.  It would better if functions isADD, isAND, isCMP, isDEC, isINC, isSUB and isTEST can be generated with tablgen.

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<mailto:amir.aupov at gmail.com>>
Sent: Thursday, December 30, 2021 4:32 PM
To: Wang, Phoebe <phoebe.wang at intel.com<mailto:phoebe.wang at intel.com>>
Cc: llvm-dev at lists.llvm.org<mailto: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<mailto:phoebe.wang at intel.com>> wrote:
Hi Amir,

It makes sense to me. Thanks!

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto: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<mailto: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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