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[llvm][DebugInfo] Emit 0/1 for constant boolean values #151225

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Merged
merged 4 commits into from
Nov 3, 2025
+40 −3
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[llvm][DebugInfo] Emit 0/1 for constant boolean values #151225

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63aa87f
[DWARF] Emit 0/1 for constant boolean values
laxmansole Jul 25, 2025
8600698
Move DW_OP_lit0/1 related change to separate PR
laxmansole Aug 21, 2025
8092f6a
Zero-extend 1-bit constantInt operands of the DbgValue
laxmansole Sep 19, 2025
0968b1f
Fixed an expected test failure caused by these changes
laxmansole Nov 3, 2025
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4 changes: 3 additions & 1 deletion llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
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Expand Up @@ -109,8 +109,10 @@ MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
if (auto *CI = dyn_cast<ConstantInt>(NumericConstant)) {
if (CI->getBitWidth() > 64)
MIB.addCImm(CI);
else
else if (CI->getBitWidth() == 1)
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@Michael137 Michael137 Sep 22, 2025

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Why are we modifying GlobalISel? I think it was working correctly there already right?

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@laxmansole laxmansole Sep 23, 2025 •
edited
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Immediate values need to be sign-extended for correctness. Consider a case where the immediate operand is a negative value.
An exception to this would be 1-bit values, as they don't have a notion of sign, and sign-extending them changes their value like 1 becomes -1.

MIB.addImm(CI->getZExtValue());
else
MIB.addImm(CI->getSExtValue());
} else if (auto *CFP = dyn_cast<ConstantFP>(NumericConstant)) {
MIB.addFPImm(CFP);
} else if (isa<ConstantPointerNull>(NumericConstant)) {
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2 changes: 2 additions & 0 deletions llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
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Expand Up @@ -733,6 +733,8 @@ MachineOperand GetMOForConstDbgOp(const SDDbgOperand &Op) {
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
if (CI->getBitWidth() > 64)
return MachineOperand::CreateCImm(CI);
if (CI->getBitWidth() == 1)
return MachineOperand::CreateImm(CI->getZExtValue());
return MachineOperand::CreateImm(CI->getSExtValue());
}
if (const ConstantFP *CF = dyn_cast<ConstantFP>(V))
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6 changes: 5 additions & 1 deletion llvm/lib/Transforms/Utils/Local.cpp
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Expand Up @@ -3416,7 +3416,11 @@ DIExpression *llvm::getExpressionForConstant(DIBuilder &DIB, const Constant &C,
// Create integer constant expression.
auto createIntegerExpression = [&DIB](const Constant &CV) -> DIExpression * {
const APInt &API = cast<ConstantInt>(&CV)->getValue();
std::optional<int64_t> InitIntOpt = API.trySExtValue();
std::optional<int64_t> InitIntOpt;
if (API.getBitWidth() == 1)
InitIntOpt = API.tryZExtValue();
else
InitIntOpt = API.trySExtValue();
return InitIntOpt ? DIB.createConstantValueExpression(
static_cast<uint64_t>(*InitIntOpt))
: nullptr;
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29 changes: 29 additions & 0 deletions llvm/test/DebugInfo/debug-bool-const-value.ll
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@@ -0,0 +1,29 @@
; REQUIRES: object-emission
; RUN: %llc_dwarf %s -filetype=obj -o - | llvm-dwarfdump - | FileCheck %s

; CHECK: {{.*}}DW_TAG_variable
; CHECK-NEXT: {{.*}} DW_AT_const_value (1)
; CHECK-NEXT: {{.*}} DW_AT_name ("arg")

define void @test() !dbg !5
{
entry:
call void @"llvm.dbg.value"(metadata i1 true, metadata !7, metadata !8), !dbg !6
ret void, !dbg !6
}

declare void @"llvm.dbg.value"(metadata %".1", metadata %".2", metadata %".3")

!llvm.dbg.cu = !{ !2 }
!llvm.module.flags = !{ !9, !10 }

!1 = !DIFile(directory: "", filename: "test")
!2 = distinct !DICompileUnit(emissionKind: FullDebug, file: !1, isOptimized: false, language: DW_LANG_C_plus_plus, runtimeVersion: 0)
!3 = !DIBasicType(encoding: DW_ATE_boolean, name: "bool", size: 8)
!4 = !DISubroutineType(types: !{null})
!5 = distinct !DISubprogram(file: !1, isDefinition: true, isLocal: false, isOptimized: false, line: 5, linkageName: "test", name: "test", scope: !1, scopeLine: 5, type: !4, unit: !2)
!6 = !DILocation(column: 1, line: 5, scope: !5)
!7 = !DILocalVariable(arg: 0, file: !1, line: 5, name: "arg", scope: !5, type: !3)
!8 = !DIExpression()
!9 = !{ i32 2, !"Dwarf Version", i32 4 }
!10 = !{ i32 2, !"Debug Info Version", i32 3 }
2 changes: 1 addition & 1 deletion llvm/unittests/Transforms/Utils/LocalTest.cpp
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Expand Up @@ -1153,7 +1153,7 @@ TEST(Local, ExpressionForConstant) {
IntegerType *Int1Ty = Type::getInt1Ty(Context);
Expr = createExpression(ConstantInt::getTrue(Context), Int1Ty);
EXPECT_NE(Expr, nullptr);
EXPECT_EQ(Expr->getElement(1), 18446744073709551615U);
EXPECT_EQ(Expr->getElement(1), 1U);

Expr = createExpression(ConstantInt::getFalse(Context), Int1Ty);
EXPECT_NE(Expr, nullptr);
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