[KeyInstr] Add bitcode support #144102
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[KeyInstr] Add bitcode support #144102
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@llvm/pr-subscribers-debuginfo Author: Orlando Cazalet-Hyams (OCHyams) ChangesPatch 4/4 adding bitcode support Full diff: https://github.com/llvm/llvm-project/pull/144102.diff 5 Files Affected:
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index fde934fbb3cf1..5f24aac2eb975 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5082,7 +5082,9 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
unsigned Line = Record[0], Col = Record[1];
unsigned ScopeID = Record[2], IAID = Record[3];
- bool isImplicitCode = Record.size() == 5 && Record[4];
+ bool isImplicitCode = Record.size() >= 5 && Record[4];
+ uint64_t AtomGroup = Record.size() == 7 ? Record[5] : 0;
+ uint8_t AtomRank = Record.size() == 7 ? Record[6] : 0;
MDNode *Scope = nullptr, *IA = nullptr;
if (ScopeID) {
@@ -5097,8 +5099,9 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
if (!IA)
return error("Invalid record");
}
+
LastLoc = DILocation::get(Scope->getContext(), Line, Col, Scope, IA,
- isImplicitCode);
+ isImplicitCode, AtomGroup, AtomRank);
I->setDebugLoc(LastLoc);
I = nullptr;
continue;
diff --git a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
index 1cd1797c1092d..538a93b168410 100644
--- a/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
+++ b/llvm/lib/Bitcode/Reader/MetadataLoader.cpp
@@ -1416,7 +1416,8 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
break;
}
case bitc::METADATA_LOCATION: {
- if (Record.size() != 5 && Record.size() != 6)
+ // 5: inlinedAt, 6: isImplicit, 8: Key Instructions fields.
+ if (Record.size() != 5 && Record.size() != 6 && Record.size() != 8)
return error("Invalid record");
IsDistinct = Record[0];
@@ -1424,10 +1425,12 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
unsigned Column = Record[2];
Metadata *Scope = getMD(Record[3]);
Metadata *InlinedAt = getMDOrNull(Record[4]);
- bool ImplicitCode = Record.size() == 6 && Record[5];
+ bool ImplicitCode = Record.size() >= 6 && Record[5];
+ uint64_t AtomGroup = Record.size() == 8 ? Record[6] : 0;
+ uint8_t AtomRank = Record.size() == 8 ? Record[7] : 0;
MetadataList.assignValue(
GET_OR_DISTINCT(DILocation, (Context, Line, Column, Scope, InlinedAt,
- ImplicitCode)),
+ ImplicitCode, AtomGroup, AtomRank)),
NextMetadataNo);
NextMetadataNo++;
break;
@@ -1857,7 +1860,7 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
break;
}
case bitc::METADATA_SUBPROGRAM: {
- if (Record.size() < 18 || Record.size() > 21)
+ if (Record.size() < 18 || Record.size() > 22)
return error("Invalid record");
bool HasSPFlags = Record[0] & 4;
@@ -1909,6 +1912,9 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
bool HasTargetFuncName = false;
unsigned OffsetA = 0;
unsigned OffsetB = 0;
+ // Key instructions won't be enabled in old-format bitcode, so only
+ // check it if HasSPFlags is true.
+ bool UsesKeyInstructions = false;
if (!HasSPFlags) {
OffsetA = 2;
OffsetB = 2;
@@ -1921,7 +1927,9 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
} else {
HasAnnotations = Record.size() >= 19;
HasTargetFuncName = Record.size() >= 20;
+ UsesKeyInstructions = Record.size() >= 21 ? Record[20] : 0;
}
+
Metadata *CUorFn = getMDOrNull(Record[12 + OffsetB]);
DISubprogram *SP = GET_OR_DISTINCT(
DISubprogram,
@@ -1947,8 +1955,8 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
HasAnnotations ? getMDOrNull(Record[18 + OffsetB])
: nullptr, // annotations
HasTargetFuncName ? getMDString(Record[19 + OffsetB])
- : nullptr // targetFuncName
- ));
+ : nullptr, // targetFuncName
+ UsesKeyInstructions));
MetadataList.assignValue(SP, NextMetadataNo);
NextMetadataNo++;
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 628b939af19ce..5afcc283c315a 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1799,12 +1799,14 @@ unsigned ModuleBitcodeWriter::createDILocationAbbrev() {
// location (it's never more expensive than building an array size 1).
auto Abbv = std::make_shared<BitCodeAbbrev>();
Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_LOCATION));
- Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
- 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));
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isDistinct
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // line
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // column
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // scope
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // inlinedAt
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isImplicitCode
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // atomGroup
+ Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // atomRank
return Stream.EmitAbbrev(std::move(Abbv));
}
@@ -1820,7 +1822,8 @@ void ModuleBitcodeWriter::writeDILocation(const DILocation *N,
Record.push_back(VE.getMetadataID(N->getScope()));
Record.push_back(VE.getMetadataOrNullID(N->getInlinedAt()));
Record.push_back(N->isImplicitCode());
-
+ Record.push_back(N->getAtomGroup());
+ Record.push_back(N->getAtomRank());
Stream.EmitRecord(bitc::METADATA_LOCATION, Record, Abbrev);
Record.clear();
}
@@ -2141,6 +2144,7 @@ void ModuleBitcodeWriter::writeDISubprogram(const DISubprogram *N,
Record.push_back(VE.getMetadataOrNullID(N->getThrownTypes().get()));
Record.push_back(VE.getMetadataOrNullID(N->getAnnotations().get()));
Record.push_back(VE.getMetadataOrNullID(N->getRawTargetFuncName()));
+ Record.push_back(N->getKeyInstructionsEnabled());
Stream.EmitRecord(bitc::METADATA_SUBPROGRAM, Record, Abbrev);
Record.clear();
@@ -3717,6 +3721,8 @@ void ModuleBitcodeWriter::writeFunction(
Vals.push_back(VE.getMetadataOrNullID(DL->getScope()));
Vals.push_back(VE.getMetadataOrNullID(DL->getInlinedAt()));
Vals.push_back(DL->isImplicitCode());
+ Vals.push_back(DL->getAtomGroup());
+ Vals.push_back(DL->getAtomRank());
Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
Vals.clear();
LastDL = DL;
diff --git a/llvm/test/DebugInfo/KeyInstructions/Generic/link-two-modes.ll b/llvm/test/DebugInfo/KeyInstructions/Generic/link-two-modes.ll
new file mode 100644
index 0000000000000..104d75d8648b6
--- /dev/null
+++ b/llvm/test/DebugInfo/KeyInstructions/Generic/link-two-modes.ll
@@ -0,0 +1,67 @@
+; RUN: split-file %s %t
+; RUN: llvm-as %t/key-instr-enabled.ll -o %t/key-instr-enabled.bc
+; RUN: llvm-as %t/key-instr-disabled.ll -o %t/key-instr-disabled.bc
+; RUN: llvm-link %t/key-instr-enabled.bc %t/key-instr-disabled.bc -o - | llvm-dis | FileCheck %s
+
+;; Check the Key Instructions metadata is preserved correctly when linking a
+;; modules with Key Instructions enabled/disabled.
+
+;; Key Instructions enabled.
+; CHECK: void @f() !dbg [[f:!.*]] {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret void, !dbg [[enabled:!.*]]
+; CHECK-NEXT: }
+
+;; Key Instructions disabled.
+; CHECK: void @g() !dbg [[g:!.*]] {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret void, !dbg [[disabled:!.*]]
+; CHECK-NEXT: }
+
+; CHECK: !llvm.dbg.cu = !{!0, !2}
+; CHECK-NEXT: !llvm.module.flags = !{!4}
+
+; CHECK: [[file1:!.*]] = !DIFile(filename: "key-instr-enabled.cpp", directory: "/")
+; CHECK: [[file2:!.*]] = !DIFile(filename: "key-instr-disabled.cpp", directory: "/")
+; CHECK: [[f]] = distinct !DISubprogram(name: "f", scope: [[file1]]{{.*}}, keyInstructions: true)
+; CHECK: [[enabled]] = !DILocation(line: 1, column: 11, scope: [[f]], atomGroup: 1, atomRank: 1)
+; CHECK: [[g]] = distinct !DISubprogram(name: "g", scope: [[file2]]
+; CHECK-NOT: keyInstructions
+; CHECK-SAME: )
+; CHECK: [[disabled]] = !DILocation(line: 1, column: 11, scope: [[g]])
+
+;--- key-instr-enabled.ll
+define dso_local void @f() !dbg !10 {
+entry:
+ ret void, !dbg !13
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "key-instr-enabled.cpp", directory: "/")
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 21.0.0git"}
+!10 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, keyInstructions: true)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null}
+!13 = !DILocation(line: 1, column: 11, scope: !10, atomGroup: 1, atomRank: 1)
+
+;--- key-instr-disabled.ll
+define dso_local void @g() !dbg !10 {
+entry:
+ ret void, !dbg !13
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "key-instr-disabled.cpp", directory: "/")
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 21.0.0git"}
+!10 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, keyInstructions: false)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null}
+!13 = !DILocation(line: 1, column: 11, scope: !10)
diff --git a/llvm/test/DebugInfo/KeyInstructions/Generic/roundtrip.ll b/llvm/test/DebugInfo/KeyInstructions/Generic/roundtrip.ll
new file mode 100644
index 0000000000000..79a06e51b264f
--- /dev/null
+++ b/llvm/test/DebugInfo/KeyInstructions/Generic/roundtrip.ll
@@ -0,0 +1,48 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt %s -o - -S | llvm-as - | llvm-dis - | FileCheck %s
+
+; Key Instructions enabled.
+define dso_local void @f() !dbg !10 {
+; CHECK-LABEL: define dso_local void @f(
+; CHECK-SAME: ) !dbg [[DBG3:![0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret void, !dbg [[DBG6:![0-9]+]]
+;
+entry:
+ ret void, !dbg !13
+}
+
+; Key Instructions disabled.
+define dso_local void @g() !dbg !14 {
+; CHECK-LABEL: define dso_local void @g(
+; CHECK-SAME: ) !dbg [[DBG7:![0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: ret void, !dbg [[DBG8:![0-9]+]]
+;
+entry:
+ ret void, !dbg !15
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "key-instr.cpp", directory: "/")
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 21.0.0git"}
+!10 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, keyInstructions: true)
+!11 = !DISubroutineType(types: !12)
+!12 = !{null}
+!13 = !DILocation(line: 1, scope: !10, atomGroup: 1, atomRank: 1)
+!14 = distinct !DISubprogram(name: "g", scope: !1, file: !1, line: 2, type: !11, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, keyInstructions: false)
+!15 = !DILocation(line: 2, scope: !14)
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+; CHECK: [[META1]] = !DIFile(filename: "{{.*}}key-instr.cpp", directory: {{.*}})
+; CHECK: [[DBG3]] = distinct !DISubprogram(name: "f", scope: [[META1]], file: [[META1]], line: 1, type: [[META4:![0-9]+]], scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: [[META0]], keyInstructions: true)
+; CHECK: [[META4]] = !DISubroutineType(types: [[META5:![0-9]+]])
+; CHECK: [[META5]] = !{null}
+; CHECK: [[DBG6]] = !DILocation(line: 1, scope: [[DBG3]], atomGroup: 1, atomRank: 1)
+; CHECK: [[DBG7]] = distinct !DISubprogram(name: "g", scope: [[META1]], file: [[META1]], line: 2, type: [[META4]], scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: [[META0]])
+; CHECK: [[DBG8]] = !DILocation(line: 2, scope: [[DBG7]])
+;.
|
jmorse
reviewed
Jun 24, 2025
| @@ -0,0 +1,48 @@ | |||
| ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5 | |||
| ; RUN: opt %s -o - -S | llvm-as - | llvm-dis - | FileCheck %s | |||
There was a problem hiding this comment.
Can't remember if there was a reason I did that... I will update this when I come to rebase it (depending on the outcome of the abbrev changes in PR 146497)
Build with support enabled and the feature on by default: compile time tracker link.
Yes and no. It's less likely that you find identical debug-locs, considering both group and rank. I considered whether it might be reasonable to change the debug-loc-again to ignore KeyInstructions info in the comparison and encode it. I didn't end up pursuing the idea, but I can look into it if you feel it's needed. |
|
Hmmm -- that's a noteworthy cost (in some scenarios up to 5%) on bitcode size (with -g). While we can rely on the position of "this is delivering a superior debugging experience" because there's strictly more information in the object-file / bitcode, it's worth going the extra mile to see if we can cut the file size increase down a bit. IIRC we talked in the past about the numeric distribution of atom-groups and how they're keyed on {Scope,InlinedAt}, thus each independent function can have its own number-sequence, but IIRC we also thought about making them globally unique-ish. Or something. The point being that with VBR-encoded atom-groups we pay a cost for high-numbers that perhaps we could avoid by being smarter? |
|
Ok, I'll do some investigating |
OCHyams
added a commit
to OCHyams/llvm-project
that referenced
this pull request
Jul 1, 2025
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 llvm#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.
Doing anything "smart" looks tricky, but I found an easy win in #146497 which seems to cover the cost of the extra fields. |
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Patch 4/4 adding bitcode support