[DebugInfo][SelectionDAGISel] Do not drop all dbg.declares if one with empty metadata is found

[Orlando]

Summary

This error was introduced (by me) in 1d1de7467c32d52926ca56b9167a2c65c451ecfa (~1 month ago).

Found while testing the D140901 patch stack. I'll rebase those changes on this because this is a clear-cut bug fix that should IMO be prioritised.

[jryans]

Thanks, this is an easy to follow bug fix and has good test coverage. 🙂

[Orlando]

Thank you for the very speedy review!

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

 static void processDbgDeclares(FunctionLoweringInfo &FuncInfo) {
   for (const BasicBlock &BB : *FuncInfo.Fn) {
     for (const Instruction &I : BB) {
       if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(&I)) {
         Value *Address = DI->getAddress();
         if (!Address) {
           LLVM_DEBUG(dbgs() << "processDbgDeclares skipping " << *DI
                             << " (bad address)\n");
-          return;
+          continue;
         }
         processDbgDeclare(FuncInfo, Address, DI->getExpression(),
                           DI->getVariable(), DI->getDebugLoc());
       }
     }
   }
 }
 

llvm/test/DebugInfo/X86/empty-metadata-dbg-declare.ll

+; RUN: llc %s -stop-after=finalize-isel -o - | FileCheck %s --implicit-check-not=DBG
+
+;; Check that a single "empty metadata" dbg.declare doesn't accidentally cause
+;; other dbg.declares in the function to go missing.
+
+; CHECK: ![[f:[0-9]+]] = !DILocalVariable(name: "f",
+
+; CHECK: stack:
+; CHECK-NEXT: - { id: 0, name: f, type: default, offset: 0, size: 4, alignment: 4,
+; CHECK-NEXT:     stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+; CHECK-NEXT:     debug-info-variable: '![[f]]', debug-info-expression: '!DIExpression()',
+; CHECK-NEXT:     debug-info-location: '{{.+}}' }
+; CHECK-NEXT: callSites:
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local void @fun() local_unnamed_addr #0 !dbg !9 {
+entry:
+  %f = alloca float
+  call void @llvm.dbg.declare(metadata ptr %f, metadata !13, metadata !DIExpression()), !dbg !15
+  call void @llvm.dbg.declare(metadata !19, metadata !18, metadata !DIExpression()), !dbg !15
+  ret void, !dbg !17
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 16.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", directory: "/")
+!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 = !{!"clang version 16.0.0"}
+!9 = distinct !DISubprogram(name: "fun", linkageName: "fun", scope: !1, file: !1, line: 2, type: !10, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
+!10 = !DISubroutineType(types: !11)
+!11 = !{null}
+!12 = !{!13}
+!13 = !DILocalVariable(name: "f", scope: !9, file: !1, line: 3, type: !14)
+!14 = !DIBasicType(name: "float", size: 32, encoding: DW_ATE_float)
+!15 = !DILocation(line: 0, scope: !9)
+!16 = !DILocation(line: 4, column: 3, scope: !9)
+!17 = !DILocation(line: 5, column: 1, scope: !9)
+!18 = !DILocalVariable(name: "g", scope: !9, file: !1, line: 3, type: !14)
+!19 = !{}