[SelectionDAG] Dump debug locs in SDNodes

[vsk]

Summary

This helps debug issues where SelectionDAG assigns the wrong location
to an instruction.

[vsk]

• Add a test.

[thegameg]

LGTM, thanks!

lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp

 #endif
 
 void SDNode::print(raw_ostream &OS, const SelectionDAG *G) const {
   printr(OS, G);
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
     if (i) OS << ", "; else OS << " ";
     printOperand(OS, G, getOperand(i));
   }
+  if (DebugLoc DL = getDebugLoc()) {
+    OS << ", ";
+    DL.print(OS);
+  }
 }

test/CodeGen/X86/selectiondag-debug-loc.ll

+; RUN: llc < %s -O1 -mtriple=x86_64-unknown-unknown -o /dev/null -debug-only=selectiondag 2>&1 | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+define i32 @main(i32 %argc, i8** %argv) !dbg !8 {
+entry:
+  %retval = alloca i32, align 4
+  %argc.addr = alloca i32, align 4
+  %argv.addr = alloca i8**, align 8
+  store i32 0, i32* %retval, align 4
+  store i32 %argc, i32* %argc.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %argc.addr, metadata !16, metadata !DIExpression()), !dbg !17
+  store i8** %argv, i8*** %argv.addr, align 8
+  call void @llvm.dbg.declare(metadata i8*** %argv.addr, metadata !18, metadata !DIExpression()), !dbg !19
+  %0 = load i8**, i8*** %argv.addr, align 8, !dbg !20
+  %1 = load i32, i32* %argc.addr, align 4, !dbg !21
+  %idxprom = sext i32 %1 to i64, !dbg !20
+  %arrayidx = getelementptr inbounds i8*, i8** %0, i64 %idxprom, !dbg !20
+  %2 = load i8*, i8** %arrayidx, align 8, !dbg !20
+  %arrayidx1 = getelementptr inbounds i8, i8* %2, i64 0, !dbg !20
+  %3 = load i8, i8* %arrayidx1, align 1, !dbg !20
+  %conv = sext i8 %3 to i32, !dbg !20
+
+  ; CHECK: ch = X86ISD::RET_FLAG t25, TargetConstant:i32<0>, Register:i32 $eax, t25:1, <stdin>:2:3
+  ret i32 %conv, !dbg !22
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 7.0.0 (trunk 330296) (llvm/trunk 330298)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "-", directory: "/Users/vsk/src/builds/llvm.org-master-RA")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 7.0.0 (trunk 330296) (llvm/trunk 330298)"}
+!8 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!9 = !DIFile(filename: "<stdin>", directory: "/Users/vsk/src/builds/llvm.org-master-RA")
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12, !12, !13}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 64)
+!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64)
+!15 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!16 = !DILocalVariable(name: "argc", arg: 1, scope: !8, file: !9, line: 1, type: !12)
+!17 = !DILocation(line: 1, column: 14, scope: !8)
+!18 = !DILocalVariable(name: "argv", arg: 2, scope: !8, file: !9, line: 1, type: !13)
+!19 = !DILocation(line: 1, column: 27, scope: !8)
+!20 = !DILocation(line: 2, column: 10, scope: !8)
+!21 = !DILocation(line: 2, column: 15, scope: !8)
+!22 = !DILocation(line: 2, column: 3, scope: !8)