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[Bitcode][NFC] Add abbrev for FUNC_CODE_DEBUG_LOC (#147211)

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DILocations that are not attached to instructions are encoded using
METADATA_LOCATION records which have an abbrev. DILocations attached to
instructions are interleaved with instruction records as FUNC_CODE_DEBUG_LOC
records, which do not have an abbrev (and FUNC_CODE_DEBUG_LOC_AGAIN
which have no operands).

Add a new FUNCTION_BLOCK abbrev FUNCTION_DEBUG_LOC_ABBREV for
FUNC_CODE_DEBUG_LOC records.

This reduces the bc file size by up to 7% in CTMark, with many between 2-4%
smaller.

[per-file file size
compile-time-tracker](https://llvm-compile-time-tracker.com/compare.php?from=75cf826849713c00829cdf657e330e24c1a2fd03&to=1e268ebd0a581016660d9d7e942495c1be041f7d&stat=size-file&details=on)
(go to stage1-ReleaseLTO-g).

This optimisation is motivated by #144102, which adds the new Key Instructions
fields to bitcode records. The combined patches still overall look to be a
slight improvement over the base.

(Originally reviewed in PR #146497)

Co-authored-by: Orlando Cazalet-Hyams <orlando.hyams@sony.com>
This commit is contained in:
Jeremy Morse 2025-07-06 22:30:31 +01:00 committed by GitHub
parent 5ccbea9f48
commit 51f4e2cda2
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 18 additions and 3 deletions
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17
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -157,6 +157,7 @@ enum {
FUNCTION_INST_CMP_ABBREV,
FUNCTION_INST_CMP_FLAGS_ABBREV,
FUNCTION_DEBUG_RECORD_VALUE_ABBREV,
FUNCTION_DEBUG_LOC_ABBREV,
};
/// Abstract class to manage the bitcode writing, subclassed for each bitcode
@ -3747,7 +3748,8 @@ void ModuleBitcodeWriter::writeFunction(
Vals.push_back(VE.getMetadataOrNullID(DL->getScope()));
Vals.push_back(VE.getMetadataOrNullID(DL->getInlinedAt()));
Vals.push_back(DL->isImplicitCode());
Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals,
FUNCTION_DEBUG_LOC_ABBREV);
Vals.clear();
LastDL = DL;
}
@ -4131,6 +4133,19 @@ void ModuleBitcodeWriter::writeBlockInfo() {
FUNCTION_DEBUG_RECORD_VALUE_ABBREV)
llvm_unreachable("Unexpected abbrev ordering! 1");
}
{
auto Abbv = std::make_shared<BitCodeAbbrev>();
Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_DEBUG_LOC));
// NOTE: No IsDistinct field for FUNC_CODE_DEBUG_LOC.
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
FUNCTION_DEBUG_LOC_ABBREV)
llvm_unreachable("Unexpected abbrev ordering!");
}
Stream.ExitBlock();
}

4
llvm/test/Bitcode/debug-loc-again.ll
View File

@ -1,9 +1,9 @@
; RUN: llvm-as < %s | llvm-bcanalyzer -dump | FileCheck %s -check-prefix=BC
; PR23436: Actually emit DEBUG_LOC_AGAIN records.
; BC: <DEBUG_LOC op
; BC: <DEBUG_LOC abbrevid
; BC: <DEBUG_LOC_AGAIN/>
; BC: <DEBUG_LOC op
; BC: <DEBUG_LOC abbrevid
; BC: <DEBUG_LOC_AGAIN/>
; RUN: llvm-as < %s | llvm-dis | FileCheck %s