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

laxmansole · 2025-07-29T20:37:13Z

Backends like NVPTX use -1 to indicate true and 0 to indicate false for boolean values. Machine instruction #DBG_VALUE also uses -1 to indicate a true boolean constant.

However, during the DWARF generation, booleans are treated as unsigned variables, and the DWARF attributes DW_AT_const_value(0xffffffffffffffff) is emitted for the True value.

This leads to the debugger printing 255 instead of "true" for boolean variables.

This change emits the attribute DW_AT_const_value(1) instead of DW_AT_const_value(0xffffffffffffffff).

github-actions · 2025-07-29T20:37:31Z

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llvmbot · 2025-07-29T20:38:01Z

@llvm/pr-subscribers-backend-nvptx

Author: Laxman (laxmansole)

Changes

For boolean values, -1 is assigned to indicate True and 0 to indicate False.
However, during the DWARF generation, booleans are treated as unsigned variables, and the debug_loc expression, like DW_OP_lit0; DW_OP_not or the attribute DW_AT_const_value(0xffffffffffffffff) is emitted for the True value.

This leads to the debugger printing 255 instead of "true" for boolean variables.

This change emits DW_OP_lit1 instead of DW_OP_lot0;DW_OP_not and the attribute DW_AT_const_value(1) instead of DW_AT_const_value(0xffffffffffffffff).

Full diff: https://github.com/llvm/llvm-project/pull/151225.diff

6 Files Affected:

(modified) llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (+32-2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (+4-2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp (+9)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h (+3)
(added) llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll (+51)
(added) llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll (+37)

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 5577a7d298177..f1be286c0a746 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -247,6 +247,13 @@ void DwarfCompileUnit::addLocationAttribute(
   DIELoc *Loc = nullptr;
   std::optional<unsigned> NVPTXAddressSpace;
   std::unique_ptr<DIEDwarfExpression> DwarfExpr;
+
+  // Check if this variable is of boolean type
+  bool isBoolean = false;
+  if (GV && GV->getType())
+    if (auto *BasicType = dyn_cast<DIBasicType>(GV->getType()))
+      isBoolean = BasicType->getEncoding() == dwarf::DW_ATE_boolean;
+
   for (const auto &GE : GlobalExprs) {
     const GlobalVariable *Global = GE.Var;
     const DIExpression *Expr = GE.Expr;
@@ -257,11 +264,17 @@ void DwarfCompileUnit::addLocationAttribute(
     // DW_AT_const_value(X).
     if (GlobalExprs.size() == 1 && Expr && Expr->isConstant()) {
       addToAccelTable = true;
+
+      // Determine the value to use, normalizing booleans to 0 or 1
+      int64_t valueToUse = Expr->getElement(1);
+      if (isBoolean)
+        valueToUse = valueToUse ? 1 : 0;
+
       addConstantValue(
           *VariableDIE,
           DIExpression::SignedOrUnsignedConstant::UnsignedConstant ==
               *Expr->isConstant(),
-          Expr->getElement(1));
+          valueToUse);
       break;
     }
 
@@ -820,6 +833,22 @@ void DwarfCompileUnit::applyConcreteDbgVariableAttributes(
   }
   if (!DVal->isVariadic()) {
     const DbgValueLocEntry *Entry = DVal->getLocEntries().begin();
+
+    // Helper function to handle boolean constant values with type safety
+    auto addConstantValueWithBooleanNormalization =
+        [&](DIE &VariableDie, uint64_t intValue, const DIType *Type) {
+          if (auto *BasicType = dyn_cast_or_null<DIBasicType>(Type)) {
+            if (BasicType->getEncoding() == dwarf::DW_ATE_boolean) {
+              // Normalize boolean values: any non-zero becomes 1, zero stays 0
+              uint64_t normalizedBoolValue = (intValue) ? 1 : 0;
+              addConstantValue(VariableDie, normalizedBoolValue, Type);
+              return;
+            }
+          }
+          // For non-boolean types, use the original constant value
+          addConstantValue(VariableDie, intValue, Type);
+        };
+
     if (Entry->isLocation()) {
       addVariableAddress(DV, VariableDie, Entry->getLoc());
     } else if (Entry->isInt()) {
@@ -836,7 +865,8 @@ void DwarfCompileUnit::applyConcreteDbgVariableAttributes(
           addUInt(VariableDie, dwarf::DW_AT_LLVM_tag_offset,
                   dwarf::DW_FORM_data1, *DwarfExpr.TagOffset);
       } else
-        addConstantValue(VariableDie, Entry->getInt(), DV.getType());
+        addConstantValueWithBooleanNormalization(VariableDie, Entry->getInt(),
+                                                 DV.getType());
     } else if (Entry->isConstantFP()) {
       addConstantFPValue(VariableDie, Entry->getConstantFP());
     } else if (Entry->isConstantInt()) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 71888332a6620..6d4c9c05e3aba 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3100,8 +3100,10 @@ void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
                             &AP](const DbgValueLocEntry &Entry,
                                  DIExpressionCursor &Cursor) -> bool {
     if (Entry.isInt()) {
-      if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
-                 BT->getEncoding() == dwarf::DW_ATE_signed_char))
+      if (BT && (BT->getEncoding() == dwarf::DW_ATE_boolean))
+        DwarfExpr.addBooleanConstant(Entry.getInt());
+      else if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
+                      BT->getEncoding() == dwarf::DW_ATE_signed_char))
         DwarfExpr.addSignedConstant(Entry.getInt());
       else
         DwarfExpr.addUnsignedConstant(Entry.getInt());
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index e684054ffa3e4..8a30714db2fdf 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -194,6 +194,15 @@ void DwarfExpression::addStackValue() {
     emitOp(dwarf::DW_OP_stack_value);
 }
 
+void DwarfExpression::addBooleanConstant(int64_t Value) {
+  assert(isImplicitLocation() || isUnknownLocation());
+  LocationKind = Implicit;
+  if (Value == 0)
+    emitOp(dwarf::DW_OP_lit0);
+  else
+    emitOp(dwarf::DW_OP_lit1);
+}
+
 void DwarfExpression::addSignedConstant(int64_t Value) {
   assert(isImplicitLocation() || isUnknownLocation());
   LocationKind = Implicit;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 06809ab263875..700e0ec5813ee 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -229,6 +229,9 @@ class DwarfExpression {
   /// This needs to be called last to commit any pending changes.
   void finalize();
 
+  /// Emit a boolean constant.
+  void addBooleanConstant(int64_t Value);
+
   /// Emit a signed constant.
   void addSignedConstant(int64_t Value);
 
diff --git a/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll b/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll
new file mode 100644
index 0000000000000..f073d51e7ef99
--- /dev/null
+++ b/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll
@@ -0,0 +1,51 @@
+; RUN: llc < %s -asm-verbose -mattr=+ptx76  -O0| FileCheck %s
+; RUN: %if ptxas %{ llc < %s -asm-verbose -mattr=+ptx76  -O0 | %ptxas-verify %}
+
+target triple = "nvptx64-nvidia-cuda"
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+; CHECK: {{.*}}section {{.*}}debug_loc
+; CHECK: .b8 48{{.*}} DW_OP_lit0
+; CHECK: .b8 49{{.*}} DW_OP_lit1
+; CHECK: .b8 144{{.*}} DW_OP_regx
+
+define void @foo(i8 %"arg.arg") !dbg !5
+{
+entry:
+  %".4" = alloca i1
+  %".5" = icmp eq i8 %"arg.arg", 0
+  %arg = alloca i1
+  br i1 %".5", label %"entry.if", label %"entry.else"
+entry.if:
+  store i1 false, i1* %arg
+  call void @"llvm.dbg.value"(metadata i1 false , metadata !9, metadata !10), !dbg !6
+  br label %"entry.endif"
+entry.else:
+  store i1 true, i1* %arg
+  call void @"llvm.dbg.value"(metadata i1 true , metadata !9, metadata !10), !dbg !7
+  br label %"entry.endif"
+entry.endif:
+  %".11" = load i1, i1* %arg
+  store i1 %".11", i1* %".4", !dbg !8
+  call void @"llvm.dbg.value"(metadata i1 %".11" , metadata !9, metadata !10), !dbg !8
+  ret void, !dbg !8
+}
+
+declare void @"llvm.dbg.value"(metadata %".1", metadata %".2", metadata %".3")
+
+!llvm.dbg.cu = !{ !2 }
+!llvm.module.flags = !{ !11, !12 }
+!nvvm.annotations = !{}
+
+!1 = !DIFile(directory: "/source/dir", filename: "test.cu")
+!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: "foo", name: "foo", scope: !1, scopeLine: 5, type: !4, unit: !2)
+!6 = !DILocation(column: 1, line: 5, scope: !5)
+!7 = !DILocation(column: 1, line: 7, scope: !5)
+!8 = !DILocation(column: 1, line: 8, scope: !5)
+!9 = !DILocalVariable(arg: 0, file: !1, line: 5, name: "arg", scope: !5, type: !3)
+!10 = !DIExpression()
+!11 = !{ i32 2, !"Dwarf Version", i32 4 }
+!12 = !{ i32 2, !"Debug Info Version", i32 3 }
\ No newline at end of file
diff --git a/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll b/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll
new file mode 100644
index 0000000000000..002a7a801c746
--- /dev/null
+++ b/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll
@@ -0,0 +1,37 @@
+; RUN: llc < %s -asm-verbose -mattr=+ptx76 | FileCheck %s
+; RUN: %if ptxas %{ llc < %s -asm-verbose -mattr=+ptx76 | %ptxas-verify %}
+
+target triple = "nvptx64-nvidia-cuda"
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+; CHECK: {{.*}}section {{.*}}debug_info
+; CHECK: {{.*}}DW_TAG_variable
+; CHECK-NEXT: {{.*}} DW_AT_address_class
+; CHECK-NEXT: .b8 1{{.*}} DW_AT_const_value
+; CHECK-NEXT: {{.*}} DW_AT_name
+
+define void @test() !dbg !5
+{
+entry:
+  %arg = alloca i1
+  store i1 true, i1* %arg, !dbg !6
+  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 }
+!nvvm.annotations = !{}
+
+!1 = !DIFile(directory: "/source/dir", filename: "test.cu")
+!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 }
\ No newline at end of file

llvmbot · 2025-07-29T20:38:02Z

@llvm/pr-subscribers-debuginfo

Author: Laxman (laxmansole)

Changes

For boolean values, -1 is assigned to indicate True and 0 to indicate False.
However, during the DWARF generation, booleans are treated as unsigned variables, and the debug_loc expression, like DW_OP_lit0; DW_OP_not or the attribute DW_AT_const_value(0xffffffffffffffff) is emitted for the True value.

This leads to the debugger printing 255 instead of "true" for boolean variables.

This change emits DW_OP_lit1 instead of DW_OP_lot0;DW_OP_not and the attribute DW_AT_const_value(1) instead of DW_AT_const_value(0xffffffffffffffff).

Full diff: https://github.com/llvm/llvm-project/pull/151225.diff

6 Files Affected:

(modified) llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (+32-2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (+4-2)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp (+9)
(modified) llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h (+3)
(added) llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll (+51)
(added) llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll (+37)

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 5577a7d298177..f1be286c0a746 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -247,6 +247,13 @@ void DwarfCompileUnit::addLocationAttribute(
   DIELoc *Loc = nullptr;
   std::optional<unsigned> NVPTXAddressSpace;
   std::unique_ptr<DIEDwarfExpression> DwarfExpr;
+
+  // Check if this variable is of boolean type
+  bool isBoolean = false;
+  if (GV && GV->getType())
+    if (auto *BasicType = dyn_cast<DIBasicType>(GV->getType()))
+      isBoolean = BasicType->getEncoding() == dwarf::DW_ATE_boolean;
+
   for (const auto &GE : GlobalExprs) {
     const GlobalVariable *Global = GE.Var;
     const DIExpression *Expr = GE.Expr;
@@ -257,11 +264,17 @@ void DwarfCompileUnit::addLocationAttribute(
     // DW_AT_const_value(X).
     if (GlobalExprs.size() == 1 && Expr && Expr->isConstant()) {
       addToAccelTable = true;
+
+      // Determine the value to use, normalizing booleans to 0 or 1
+      int64_t valueToUse = Expr->getElement(1);
+      if (isBoolean)
+        valueToUse = valueToUse ? 1 : 0;
+
       addConstantValue(
           *VariableDIE,
           DIExpression::SignedOrUnsignedConstant::UnsignedConstant ==
               *Expr->isConstant(),
-          Expr->getElement(1));
+          valueToUse);
       break;
     }
 
@@ -820,6 +833,22 @@ void DwarfCompileUnit::applyConcreteDbgVariableAttributes(
   }
   if (!DVal->isVariadic()) {
     const DbgValueLocEntry *Entry = DVal->getLocEntries().begin();
+
+    // Helper function to handle boolean constant values with type safety
+    auto addConstantValueWithBooleanNormalization =
+        [&](DIE &VariableDie, uint64_t intValue, const DIType *Type) {
+          if (auto *BasicType = dyn_cast_or_null<DIBasicType>(Type)) {
+            if (BasicType->getEncoding() == dwarf::DW_ATE_boolean) {
+              // Normalize boolean values: any non-zero becomes 1, zero stays 0
+              uint64_t normalizedBoolValue = (intValue) ? 1 : 0;
+              addConstantValue(VariableDie, normalizedBoolValue, Type);
+              return;
+            }
+          }
+          // For non-boolean types, use the original constant value
+          addConstantValue(VariableDie, intValue, Type);
+        };
+
     if (Entry->isLocation()) {
       addVariableAddress(DV, VariableDie, Entry->getLoc());
     } else if (Entry->isInt()) {
@@ -836,7 +865,8 @@ void DwarfCompileUnit::applyConcreteDbgVariableAttributes(
           addUInt(VariableDie, dwarf::DW_AT_LLVM_tag_offset,
                   dwarf::DW_FORM_data1, *DwarfExpr.TagOffset);
       } else
-        addConstantValue(VariableDie, Entry->getInt(), DV.getType());
+        addConstantValueWithBooleanNormalization(VariableDie, Entry->getInt(),
+                                                 DV.getType());
     } else if (Entry->isConstantFP()) {
       addConstantFPValue(VariableDie, Entry->getConstantFP());
     } else if (Entry->isConstantInt()) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 71888332a6620..6d4c9c05e3aba 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3100,8 +3100,10 @@ void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
                             &AP](const DbgValueLocEntry &Entry,
                                  DIExpressionCursor &Cursor) -> bool {
     if (Entry.isInt()) {
-      if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
-                 BT->getEncoding() == dwarf::DW_ATE_signed_char))
+      if (BT && (BT->getEncoding() == dwarf::DW_ATE_boolean))
+        DwarfExpr.addBooleanConstant(Entry.getInt());
+      else if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
+                      BT->getEncoding() == dwarf::DW_ATE_signed_char))
         DwarfExpr.addSignedConstant(Entry.getInt());
       else
         DwarfExpr.addUnsignedConstant(Entry.getInt());
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index e684054ffa3e4..8a30714db2fdf 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -194,6 +194,15 @@ void DwarfExpression::addStackValue() {
     emitOp(dwarf::DW_OP_stack_value);
 }
 
+void DwarfExpression::addBooleanConstant(int64_t Value) {
+  assert(isImplicitLocation() || isUnknownLocation());
+  LocationKind = Implicit;
+  if (Value == 0)
+    emitOp(dwarf::DW_OP_lit0);
+  else
+    emitOp(dwarf::DW_OP_lit1);
+}
+
 void DwarfExpression::addSignedConstant(int64_t Value) {
   assert(isImplicitLocation() || isUnknownLocation());
   LocationKind = Implicit;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 06809ab263875..700e0ec5813ee 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -229,6 +229,9 @@ class DwarfExpression {
   /// This needs to be called last to commit any pending changes.
   void finalize();
 
+  /// Emit a boolean constant.
+  void addBooleanConstant(int64_t Value);
+
   /// Emit a signed constant.
   void addSignedConstant(int64_t Value);
 
diff --git a/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll b/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll
new file mode 100644
index 0000000000000..f073d51e7ef99
--- /dev/null
+++ b/llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll
@@ -0,0 +1,51 @@
+; RUN: llc < %s -asm-verbose -mattr=+ptx76  -O0| FileCheck %s
+; RUN: %if ptxas %{ llc < %s -asm-verbose -mattr=+ptx76  -O0 | %ptxas-verify %}
+
+target triple = "nvptx64-nvidia-cuda"
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+; CHECK: {{.*}}section {{.*}}debug_loc
+; CHECK: .b8 48{{.*}} DW_OP_lit0
+; CHECK: .b8 49{{.*}} DW_OP_lit1
+; CHECK: .b8 144{{.*}} DW_OP_regx
+
+define void @foo(i8 %"arg.arg") !dbg !5
+{
+entry:
+  %".4" = alloca i1
+  %".5" = icmp eq i8 %"arg.arg", 0
+  %arg = alloca i1
+  br i1 %".5", label %"entry.if", label %"entry.else"
+entry.if:
+  store i1 false, i1* %arg
+  call void @"llvm.dbg.value"(metadata i1 false , metadata !9, metadata !10), !dbg !6
+  br label %"entry.endif"
+entry.else:
+  store i1 true, i1* %arg
+  call void @"llvm.dbg.value"(metadata i1 true , metadata !9, metadata !10), !dbg !7
+  br label %"entry.endif"
+entry.endif:
+  %".11" = load i1, i1* %arg
+  store i1 %".11", i1* %".4", !dbg !8
+  call void @"llvm.dbg.value"(metadata i1 %".11" , metadata !9, metadata !10), !dbg !8
+  ret void, !dbg !8
+}
+
+declare void @"llvm.dbg.value"(metadata %".1", metadata %".2", metadata %".3")
+
+!llvm.dbg.cu = !{ !2 }
+!llvm.module.flags = !{ !11, !12 }
+!nvvm.annotations = !{}
+
+!1 = !DIFile(directory: "/source/dir", filename: "test.cu")
+!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: "foo", name: "foo", scope: !1, scopeLine: 5, type: !4, unit: !2)
+!6 = !DILocation(column: 1, line: 5, scope: !5)
+!7 = !DILocation(column: 1, line: 7, scope: !5)
+!8 = !DILocation(column: 1, line: 8, scope: !5)
+!9 = !DILocalVariable(arg: 0, file: !1, line: 5, name: "arg", scope: !5, type: !3)
+!10 = !DIExpression()
+!11 = !{ i32 2, !"Dwarf Version", i32 4 }
+!12 = !{ i32 2, !"Debug Info Version", i32 3 }
\ No newline at end of file
diff --git a/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll b/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll
new file mode 100644
index 0000000000000..002a7a801c746
--- /dev/null
+++ b/llvm/test/DebugInfo/NVPTX/debug-bool-const-value.ll
@@ -0,0 +1,37 @@
+; RUN: llc < %s -asm-verbose -mattr=+ptx76 | FileCheck %s
+; RUN: %if ptxas %{ llc < %s -asm-verbose -mattr=+ptx76 | %ptxas-verify %}
+
+target triple = "nvptx64-nvidia-cuda"
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+; CHECK: {{.*}}section {{.*}}debug_info
+; CHECK: {{.*}}DW_TAG_variable
+; CHECK-NEXT: {{.*}} DW_AT_address_class
+; CHECK-NEXT: .b8 1{{.*}} DW_AT_const_value
+; CHECK-NEXT: {{.*}} DW_AT_name
+
+define void @test() !dbg !5
+{
+entry:
+  %arg = alloca i1
+  store i1 true, i1* %arg, !dbg !6
+  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 }
+!nvvm.annotations = !{}
+
+!1 = !DIFile(directory: "/source/dir", filename: "test.cu")
+!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 }
\ No newline at end of file

laxmansole · 2025-07-29T21:13:15Z

CC: @enferex

laxmansole · 2025-07-31T18:56:53Z

CC: @jmorse

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

Michael137 · 2025-08-06T08:48:41Z

This leads to the debugger printing 255 instead of "true" for boolean variables.

Do you have an example/Github issue of this? Shouldn't the debugger know how to present booleans in a particular language, regardless of which non-zero value was used to indicate truthness?

dwblaikie · 2025-08-06T18:19:14Z

This leads to the debugger printing 255 instead of "true" for boolean variables.

Do you have an example/Github issue of this? Shouldn't the debugger know how to present booleans in a particular language, regardless of which non-zero value was used to indicate truthness?

Arguable - it's UB to have a bool that isn't 0 or 1 (-fsanitize=bool catches this, for instance - there's some neat term for these sort of "corrupted" bools, but I forget what it is) so I'd expect a debugger to show the actual value and say something about the value being invalid. This'd help the developer understand why boolean tests (if (x) or if (!x)) don't work necessarily work as expected.

So, yeah, I think it is important we describe the value as 0 or 1 if it is 0 or 1, conceptually, at least.

dwblaikie · 2025-08-06T18:19:26Z

(but yeah, still would be good to see a bug/etc)

laxmansole · 2025-08-11T18:38:44Z

(but yeah, still would be good to see a bug/etc)

We encountered this issue with cuda-gdb. I won't be able to share the high-level source, but I have added shorter LLVM IR lit tests that generate this DWARF.

laxmansole · 2025-08-18T17:44:39Z

ping

Michael137 · 2025-08-19T14:13:28Z

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -820,6 +833,22 @@ void DwarfCompileUnit::applyConcreteDbgVariableAttributes(
  }
  if (!DVal->isVariadic()) {
    const DbgValueLocEntry *Entry = DVal->getLocEntries().begin();
+
+    // Helper function to handle boolean constant values with type safety
+    auto addConstantValueWithBooleanNormalization =


Have you considered putting this boolean normalization into addConstantValue? That way, any other place where we emit booleans with out-of-range constants would benefit from this. Some of the overloads don't take a DIType though, so might not be as simple as I imagine?

I wasn't sure if adding boolean normalization for the APInt or ConstantInt versions made sense, so I only modified the affected call sites.

I guess what's confusing me is:

Who is assigning -1 to indicate true?

There seem to be two independent changes in this PR:

emit DW_OP_lit for boolean constants when computing debug values. This seems very reasonable since it makes the DWARF expression simpler (and works regardless of how the true/false values are represented?)

Don't emit DW_OP_constu (-1) values for booleans. That also seems reasonable, but what I'm curious about where this -1 comes from? And then, if you do this kind of normalization for booleans here, why not any other place where DW_AT_const_value is emitted for booleans? You don't strictly have to but I think we can split these two changes into separate PRs

Who is assigning -1 to indicate true?

llvm-project/llvm/include/llvm/CodeGen/TargetLowering.h

Lines 236 to 241 in 085d0b0

/// Enum that describes how the target represents true/false values.

enum BooleanContent {

UndefinedBooleanContent, // Only bit 0 counts, the rest can hold garbage.

ZeroOrOneBooleanContent, // All bits zero except for bit 0.

ZeroOrNegativeOneBooleanContent // All bits equal to bit 0.

};

There is a target-dependent setBooleanContents.

While creating #DBG_VALUE, the true/1 gets signed extednded to 0xffffffffffffffff i.e. -1(Line 736 below)

llvm-project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp

Lines 731 to 749 in 5886a27

MachineOperand GetMOForConstDbgOp(const SDDbgOperand &Op) {

const Value *V = Op.getConst();

if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {

if (CI->getBitWidth() > 64)

return MachineOperand::CreateCImm(CI);

return MachineOperand::CreateImm(CI->getSExtValue());

}

if (const ConstantFP *CF = dyn_cast<ConstantFP>(V))

return MachineOperand::CreateFPImm(CF);

// Note: This assumes that all nullptr constants are zero-valued.

if (isa<ConstantPointerNull>(V))

return MachineOperand::CreateImm(0);

// Undef or unhandled value type, so return an undef operand.

return MachineOperand::CreateReg(

/* Reg */ 0U, /* isDef */ false, /* isImp */ false,

/* isKill */ false, /* isDead */ false,

/* isUndef */ false, /* isEarlyClobber */ false,

/* SubReg */ 0, /* isDebug */ true);

}

And then, if you do this kind of normalization for booleans here, why not any other place where DW_AT_const_value is emitted for booleans?

I checked all the call sites for addConstantValue and found that this is the most relevant one. Alternatively, as you suggested, I could add this normalization to addConstantValue, but we don't have DIType in all overloaded functions.

I think we can split these two changes into separate PRs

Sure. Let me spilt these into two separate PRs- current one for the changes in DwarfCompileUnit.cpp and another one for the changes to emit DW_OP_lit0/1 for booleans.

emit DW_OP_lit for boolean constants when computing debug values.

Created a separate PR #155539 for these changes

llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll

llvm/test/DebugInfo/debug-bool-const-location.ll

llvmbot added llvm:codegen debuginfo backend:NVPTX labels Jul 29, 2025

Michael137 reviewed Aug 6, 2025

View reviewed changes

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp Outdated Show resolved Hide resolved

Michael137 requested a review from dwblaikie August 6, 2025 08:46

laxmansole requested a review from Michael137 August 11, 2025 18:40

Michael137 reviewed Aug 19, 2025

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llvm/test/DebugInfo/NVPTX/debug-bool-const-location.ll Outdated Show resolved Hide resolved

laxmansole force-pushed the user/lsole/boolean_constants_as_literals branch from 5810b2f to f9104e6 Compare August 21, 2025 02:01

Michael137 reviewed Aug 22, 2025

View reviewed changes

llvm/test/DebugInfo/debug-bool-const-location.ll Outdated Show resolved Hide resolved

laxmansole force-pushed the user/lsole/boolean_constants_as_literals branch from f9104e6 to a3fbfa6 Compare August 25, 2025 20:26

laxmansole mentioned this pull request Aug 27, 2025

Emit DW_OP_lit0/1 for constant boolean values #155539

Merged

laxmansole added 2 commits August 26, 2025 19:12

[DWARF] Emit 0/1 for constant boolean values

a5e96cd

Move DW_OP_lit0/1 related change to separate PR

859a086

laxmansole force-pushed the user/lsole/boolean_constants_as_literals branch from a3fbfa6 to 859a086 Compare August 27, 2025 02:36

	/// Enum that describes how the target represents true/false values.
	enum BooleanContent {
	UndefinedBooleanContent, // Only bit 0 counts, the rest can hold garbage.
	ZeroOrOneBooleanContent, // All bits zero except for bit 0.
	ZeroOrNegativeOneBooleanContent // All bits equal to bit 0.
	};

	MachineOperand GetMOForConstDbgOp(const SDDbgOperand &Op) {
	const Value *V = Op.getConst();
	if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
	if (CI->getBitWidth() > 64)
	return MachineOperand::CreateCImm(CI);
	return MachineOperand::CreateImm(CI->getSExtValue());
	}
	if (const ConstantFP *CF = dyn_cast<ConstantFP>(V))
	return MachineOperand::CreateFPImm(CF);
	// Note: This assumes that all nullptr constants are zero-valued.
	if (isa<ConstantPointerNull>(V))
	return MachineOperand::CreateImm(0);
	// Undef or unhandled value type, so return an undef operand.
	return MachineOperand::CreateReg(
	/* Reg / 0U, / isDef / false, / isImp */ false,
	/* isKill / false, / isDead */ false,
	/* isUndef / false, / isEarlyClobber */ false,
	/* SubReg / 0, / isDebug */ true);
	}

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

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

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