[DebugInfo] Assign best possible debugloc to bundle

[quic-santdas]

The debug info attached to the BUNDLE is the first instruction in the BUNDLE, even if a better debug info (line:column) is present in the later instructions of the bundle. The patch tries to get a better debug info first. If not, then a worse debug info without line number is chosen.

[llvmbot]

@llvm/pr-subscribers-debuginfo

Author: Santanu Das (quic-santdas)

Changes

The debug info attached to the BUNDLE is the first instruction in the BUNDLE, even if a better debug info (line:column) is present in the later instructions of the bundle. The patch tries to get a better debug info first. If not, then a worse debug info without line number is chosen.

---

Full diff: https://github.com/llvm/llvm-project/pull/164573.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/MachineInstrBundle.cpp (+11-4)
• (added) llvm/test/DebugInfo/Hexagon/packet-debug.ll (+96)

diff --git a/llvm/lib/CodeGen/MachineInstrBundle.cpp b/llvm/lib/CodeGen/MachineInstrBundle.cpp
index da29ffc9d2fed..a749b13846e0c 100644
--- a/llvm/lib/CodeGen/MachineInstrBundle.cpp
+++ b/llvm/lib/CodeGen/MachineInstrBundle.cpp
@@ -88,10 +88,17 @@ llvm::createUnpackMachineBundles(
 /// DILocation is found, then an empty location is returned.
 static DebugLoc getDebugLoc(MachineBasicBlock::instr_iterator FirstMI,
                             MachineBasicBlock::instr_iterator LastMI) {
-  for (auto MII = FirstMI; MII != LastMI; ++MII)
-    if (MII->getDebugLoc())
-      return MII->getDebugLoc();
-  return DebugLoc();
+  DebugLoc DL;
+  for (auto MII = FirstMI; MII != LastMI; ++MII) {
+    DebugLoc MIIDL = MII->getDebugLoc();
+    if (MIIDL) {
+      if (MIIDL.getLine() == 0)
+        DL = MIIDL.get();
+      else
+        return MII->getDebugLoc();
+    }
+  }
+  return DL;
 }
 
 /// Check if target reg is contained in given lists, which are:
diff --git a/llvm/test/DebugInfo/Hexagon/packet-debug.ll b/llvm/test/DebugInfo/Hexagon/packet-debug.ll
new file mode 100644
index 0000000000000..ad1b04bbf400f
--- /dev/null
+++ b/llvm/test/DebugInfo/Hexagon/packet-debug.ll
@@ -0,0 +1,96 @@
+; Passes if line number 9 is generated in the line table
+
+; REQUIRES: hexagon-registered-target
+
+; RUN: llc %s -march=hexagon -filetype=obj -mcpu=hexagonv69 -o - | llvm-dwarfdump --debug-line - | FileCheck %s
+
+; CHECK: 9 9 1 0 0 0 is_stmt prologue_end
+
+@glob = common dso_local local_unnamed_addr global i32 0, align 4, !dbg !0
+@.str = private unnamed_addr constant [23 x i8] c"Factorial of %d is %d\0A\00", align 1, !dbg !5
+define dso_local i32 @factorial(i32 %i) local_unnamed_addr !dbg !18 {
+entry:
+    #dbg_value(i32 %i, !22, !DIExpression(), !24)
+  %cmp = icmp eq i32 %i, 1, !dbg !25
+  br i1 %cmp, label %common.ret, label %if.end, !dbg !25
+common.ret:                                       ; preds = %entry, %if.end
+  %common.ret.op = phi i32 [ %mul, %if.end ], [ 1, %entry ]
+  ret i32 %common.ret.op, !dbg !27
+if.end:                                           ; preds = %entry
+  %sub = add nsw i32 %i, -1, !dbg !28
+  %call = tail call i32 @factorial(i32 noundef %sub), !dbg !29
+  %mul = mul nsw i32 %call, %i, !dbg !30
+    #dbg_value(i32 %mul, !23, !DIExpression(), !24)
+  store i32 %mul, ptr @glob, align 4, !dbg !31, !tbaa !32
+  br label %common.ret, !dbg !27
+}
+define dso_local noundef i32 @main(i32 noundef %argc, ptr noundef readnone captures(none) %argv) local_unnamed_addr !dbg !36 {
+entry:
+    #dbg_value(i32 %argc, !42, !DIExpression(), !46)
+    #dbg_value(ptr %argv, !43, !DIExpression(), !46)
+    #dbg_value(i32 10, !44, !DIExpression(), !46)
+  %call = tail call i32 @factorial(i32 noundef 10), !dbg !47
+  %call1 = tail call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str, i32 noundef 10, i32 noundef %call), !dbg !48
+  ret i32 0, !dbg !50
+}
+declare !dbg !51 dso_local noundef i32 @printf(ptr noundef readonly captures(none), ...) local_unnamed_addr #1
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!12, !13, !14, !15, !16}
+!llvm.ident = !{!17}
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "glob", scope: !2, file: !3, line: 4, type: !11, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "QuIC LLVM Hexagon Clang version 21.0 Engineering Release: hexagon-clang-210", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, debugInfoForProfiling: true, nameTableKind: None)
+!3 = !DIFile(filename: "fact.c", directory: ".")
+!4 = !{!5, !0}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(scope: null, file: !3, line: 38, type: !7, isLocal: true, isDefinition: true)
+!7 = !DICompositeType(tag: DW_TAG_array_type, baseType: !8, size: 184, elements: !9)
+!8 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_unsigned_char)
+!9 = !{!10}
+!10 = !DISubrange(count: 23)
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{i32 7, !"Dwarf Version", i32 4}
+!13 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{i32 1, !"wchar_size", i32 4}
+!15 = !{i32 7, !"frame-pointer", i32 2}
+!16 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!17 = !{!"QuIC LLVM Hexagon Clang version 21.0 Engineering Release: hexagon-clang-210"}
+!18 = distinct !DISubprogram(name: "factorial", scope: !3, file: !3, line: 6, type: !19, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !21)
+!19 = !DISubroutineType(types: !20)
+!20 = !{!11, !11}
+!21 = !{!22, !23}
+!22 = !DILocalVariable(name: "i", arg: 1, scope: !18, file: !3, line: 6, type: !11)
+!23 = !DILocalVariable(name: "j", scope: !18, file: !3, line: 8, type: !11)
+!24 = !DILocation(line: 0, scope: !18)
+!25 = !DILocation(line: 9, column: 9, scope: !26)
+!26 = distinct !DILexicalBlock(scope: !18, file: !3, line: 9, column: 7)
+!27 = !DILocation(line: 14, column: 1, scope: !18)
+!28 = !DILocation(line: 11, column: 23, scope: !18)
+!29 = !DILocation(line: 11, column: 11, scope: !18)
+!30 = !DILocation(line: 11, column: 9, scope: !18)
+!31 = !DILocation(line: 12, column: 8, scope: !18)
+!32 = !{!33, !33, i64 0}
+!33 = !{!"int", !34, i64 0}
+!34 = !{!"omnipotent char", !35, i64 0}
+!35 = !{!"Simple C/C++ TBAA"}
+!36 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 16, type: !37, scopeLine: 17, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !41)
+!37 = !DISubroutineType(types: !38)
+!38 = !{!11, !11, !39}
+!39 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !40, size: 32)
+!40 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !8, size: 32)
+!41 = !{!42, !43, !44}
+!42 = !DILocalVariable(name: "argc", arg: 1, scope: !36, file: !3, line: 16, type: !11)
+!43 = !DILocalVariable(name: "argv", arg: 2, scope: !36, file: !3, line: 16, type: !39)
+!44 = !DILocalVariable(name: "base", scope: !36, file: !3, line: 18, type: !45)
+!45 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!46 = !DILocation(line: 0, scope: !36)
+!47 = !DILocation(line: 38, column: 43, scope: !36)
+!48 = !DILocation(line: 38, column: 3, scope: !49)
+!49 = !DILexicalBlockFile(scope: !36, file: !3, discriminator: 2)
+!50 = !DILocation(line: 39, column: 3, scope: !36)
+!51 = !DISubprogram(name: "printf", scope: !52, file: !52, line: 160, type: !53, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
+!52 = !DIFile(filename: "stdio.h", directory: ".")
+!53 = !DISubroutineType(types: !54)
+!54 = !{!11, !55, null}
+!55 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !56, size: 32)
+!56 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !8)

[dzhidzhoev]

If a separate folder for Hexagon-dependent tests is created, should it contain lit.local.cfg similar to llvm/test/DebugInfo/X86/lit.local.cfg or llvm/test/DebugInfo/AArch64/lit.local.cfg?

if not "Hexagon" in config.root.targets:
    config.unsupported = True

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[quic-santdas]

@androm3da @iajbar

[OCHyams]

From a debug info perspective I don't have a good handle on what's best to do with a bundle, but I've got some general patch feedback.

I think the test could be minimised a little more? e.g.

• remove #dbg_values
• looks like there's many !dbg / DILocations that are not needed
• the whole llc pipeline is run; can this be narrowed down to a specific pass using --start-before --stop-after?

[OCHyams]

I think the function's comment needs updating?