[llvm] [Dwarf] Emit `DW_AT_bit_size` for non-byte-sized types (PR #137118)
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Wed Apr 23 22:46:15 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-debuginfo
Author: Yingwei Zheng (dtcxzyw)
<details>
<summary>Changes</summary>
When the base type is non-byte-sized (e.g., boolean), we should emit `DW_AT_bit_size` to make `DW_OP_convert` correct.
This patch was tested with gdb. lldb ignores `DW_AT_bit_size` field if `DW_AT_byte_size` is available. I will post a follow-up patch later.
This patch is stacked on https://github.com/llvm/llvm-project/pull/137013
Related issue: https://github.com/llvm/llvm-project/issues/71065
---
Full diff: https://github.com/llvm/llvm-project/pull/137118.diff
4 Files Affected:
- (modified) llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (+4)
- (modified) llvm/lib/Transforms/InstCombine/InstructionCombining.cpp (+18)
- (added) llvm/test/DebugInfo/X86/convert-bool.ll (+43)
- (added) llvm/test/Transforms/InstCombine/debuginfo-invert.ll (+70)
``````````diff
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 3939dae81841f..e73028d2e28d9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1749,6 +1749,10 @@ void DwarfCompileUnit::createBaseTypeDIEs() {
// Round up to smallest number of bytes that contains this number of bits.
addUInt(Die, dwarf::DW_AT_byte_size, std::nullopt,
divideCeil(Btr.BitSize, 8));
+ // If the size is not a multiple of 8 (e.g., boolean), add the bit size
+ // field.
+ if (Btr.BitSize % 8 != 0)
+ addUInt(Die, dwarf::DW_AT_bit_size, std::nullopt, Btr.BitSize);
Btr.Die = &Die;
}
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index f807f5f4519fc..c47d32dc01cd3 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1396,6 +1396,24 @@ void InstCombinerImpl::freelyInvertAllUsersOf(Value *I, Value *IgnoredUser) {
"canFreelyInvertAllUsersOf() ?");
}
}
+
+ // Update pre-existing debug value uses.
+ SmallVector<DbgValueInst *, 4> DbgValues;
+ SmallVector<DbgVariableRecord *, 4> DbgVariableRecords;
+ llvm::findDbgValues(DbgValues, I, &DbgVariableRecords);
+ auto ApplyNot = [](DIExpression *Src) {
+ SmallVector<uint64_t> Elements;
+ Elements.reserve(Src->getElements().size() + 1);
+ Elements.push_back(dwarf::DW_OP_not);
+ Elements.append(Src->getElements().begin(), Src->getElements().end());
+ return DIExpression::get(Src->getContext(), Elements);
+ };
+
+ for (auto *DVI : DbgValues)
+ DVI->setExpression(ApplyNot(DVI->getExpression()));
+
+ for (DbgVariableRecord *DVR : DbgVariableRecords)
+ DVR->setExpression(ApplyNot(DVR->getExpression()));
}
/// Given a 'sub' instruction, return the RHS of the instruction if the LHS is a
diff --git a/llvm/test/DebugInfo/X86/convert-bool.ll b/llvm/test/DebugInfo/X86/convert-bool.ll
new file mode 100644
index 0000000000000..0abd011c56668
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/convert-bool.ll
@@ -0,0 +1,43 @@
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -filetype=obj -O0 < %s | llvm-dwarfdump - | FileCheck %s
+
+; CHECK: DW_TAG_base_type
+; CHECK-NEXT: DW_AT_name ("DW_ATE_unsigned_1")
+; CHECK-NEXT: DW_AT_encoding (DW_ATE_unsigned)
+; CHECK-NEXT: DW_AT_byte_size (0x01)
+; CHECK-NEXT: DW_AT_bit_size (0x01)
+
+define void @main() !dbg !18 {
+entry:
+ #dbg_value(i1 false, !22, !DIExpression(DW_OP_not, DW_OP_LLVM_convert, 1, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value), !23)
+ ret void, !dbg !24
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!10, !11, !12, !13, !14, !15, !16}
+!llvm.ident = !{!17}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 21.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.c", directory: "/home/dtcxzyw/WorkSpace/Projects/compilers/LLVM/llvm-build", checksumkind: CSK_MD5, checksum: "100bdbce655d729c24c7c0e8523a58ae")
+!2 = !{!3, !6, !8}
+!3 = !DIGlobalVariableExpression(var: !4, expr: !DIExpression())
+!4 = distinct !DIGlobalVariable(name: "a", scope: !0, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true)
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "b", scope: !0, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true)
+!8 = !DIGlobalVariableExpression(var: !9, expr: !DIExpression())
+!9 = distinct !DIGlobalVariable(name: "c", scope: !0, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true)
+!10 = !{i32 7, !"Dwarf Version", i32 5}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{i32 8, !"PIC Level", i32 2}
+!14 = !{i32 7, !"PIE Level", i32 2}
+!15 = !{i32 7, !"uwtable", i32 2}
+!16 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!17 = !{!"clang version 21.0.0git"}
+!18 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 3, type: !19, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !21)
+!19 = !DISubroutineType(types: !20)
+!20 = !{null}
+!21 = !{!22}
+!22 = !DILocalVariable(name: "l_4516", scope: !18, file: !1, line: 4, type: !5)
+!23 = !DILocation(line: 0, scope: !18)
+!24 = !DILocation(line: 9, column: 1, scope: !18)
diff --git a/llvm/test/Transforms/InstCombine/debuginfo-invert.ll b/llvm/test/Transforms/InstCombine/debuginfo-invert.ll
new file mode 100644
index 0000000000000..8c673e319f7f7
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/debuginfo-invert.ll
@@ -0,0 +1,70 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=instcombine -S %s -o - | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @test(i32 noundef %x, i32 noundef %y) !dbg !10 {
+; CHECK-LABEL: define i32 @test(
+; CHECK-SAME: i32 noundef [[X:%.*]], i32 noundef [[Y:%.*]]) !dbg [[DBG10:![0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: #dbg_value(i32 [[X]], [[META15:![0-9]+]], !DIExpression(), [[META18:![0-9]+]])
+; CHECK-NEXT: #dbg_value(i32 [[Y]], [[META16:![0-9]+]], !DIExpression(), [[META18]])
+; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq i32 [[X]], 0, !dbg [[DBG19:![0-9]+]]
+; CHECK-NEXT: #dbg_value(i1 [[CMP_NOT]], [[META17:![0-9]+]], !DIExpression(DW_OP_not, DW_OP_LLVM_convert, 1, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value), [[META18]])
+; CHECK-NEXT: [[TMP0:%.*]] = and i32 [[Y]], 1, !dbg [[DBG20:![0-9]+]]
+; CHECK-NEXT: [[AND:%.*]] = select i1 [[CMP_NOT]], i32 0, i32 [[TMP0]], !dbg [[DBG20]]
+; CHECK-NEXT: ret i32 [[AND]], !dbg [[DBG21:![0-9]+]]
+;
+entry:
+ #dbg_value(i32 %x, !15, !DIExpression(), !18)
+ #dbg_value(i32 %y, !16, !DIExpression(), !18)
+ %cmp = icmp ne i32 %x, 0, !dbg !19
+ %conv = zext i1 %cmp to i32, !dbg !19
+ #dbg_value(i32 %conv, !17, !DIExpression(), !18)
+ %and = and i32 %conv, %y, !dbg !20
+ ret i32 %and, !dbg !21
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 21.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.c", directory: "/", checksumkind: CSK_MD5, checksum: "b2d9ffc7905684d8b7c3b52a3136e57c")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!6 = !{i32 7, !"PIE Level", i32 2}
+!7 = !{i32 7, !"uwtable", i32 2}
+!8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!9 = !{!"clang version 21.0.0git"}
+!10 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !14)
+!11 = !DISubroutineType(types: !12)
+!12 = !{!13, !13, !13}
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !{!15, !16, !17}
+!15 = !DILocalVariable(name: "x", arg: 1, scope: !10, file: !1, line: 1, type: !13)
+!16 = !DILocalVariable(name: "y", arg: 2, scope: !10, file: !1, line: 1, type: !13)
+!17 = !DILocalVariable(name: "z", scope: !10, file: !1, line: 2, type: !13)
+!18 = !DILocation(line: 0, scope: !10)
+!19 = !DILocation(line: 2, column: 13, scope: !10)
+!20 = !DILocation(line: 3, column: 12, scope: !10)
+!21 = !DILocation(line: 3, column: 3, scope: !10)
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C11, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+; CHECK: [[META1]] = !DIFile(filename: "test.c", directory: {{.*}})
+; CHECK: [[DBG10]] = distinct !DISubprogram(name: "test", scope: [[META1]], file: [[META1]], line: 1, type: [[META11:![0-9]+]], scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META14:![0-9]+]])
+; CHECK: [[META11]] = !DISubroutineType(types: [[META12:![0-9]+]])
+; CHECK: [[META12]] = !{[[META13:![0-9]+]], [[META13]], [[META13]]}
+; CHECK: [[META13]] = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+; CHECK: [[META14]] = !{[[META15]], [[META16]], [[META17]]}
+; CHECK: [[META15]] = !DILocalVariable(name: "x", arg: 1, scope: [[DBG10]], file: [[META1]], line: 1, type: [[META13]])
+; CHECK: [[META16]] = !DILocalVariable(name: "y", arg: 2, scope: [[DBG10]], file: [[META1]], line: 1, type: [[META13]])
+; CHECK: [[META17]] = !DILocalVariable(name: "z", scope: [[DBG10]], file: [[META1]], line: 2, type: [[META13]])
+; CHECK: [[META18]] = !DILocation(line: 0, scope: [[DBG10]])
+; CHECK: [[DBG19]] = !DILocation(line: 2, column: 13, scope: [[DBG10]])
+; CHECK: [[DBG20]] = !DILocation(line: 3, column: 12, scope: [[DBG10]])
+; CHECK: [[DBG21]] = !DILocation(line: 3, column: 3, scope: [[DBG10]])
+;.
``````````
</details>
https://github.com/llvm/llvm-project/pull/137118
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