Reapply "[DebugInfo] Prevent explosion of debug intrinsics during jump threading"

        continue;

      while (ProcessBlock(&BB)) // Thread all of the branches we can over BB.

        Changed = true;

      // Jump threading may have introduced redundant debug values into BB

      // which should be removed.

      if (Changed)

        RemoveRedundantDbgInstrs(&BB);

      // Stop processing BB if it's the entry or is now deleted. The following

      // routines attempt to eliminate BB and locating a suitable replacement

      // for the entry is non-trivial.

      // ProcessBlock doesn't thread BBs with unconditional TIs. However, if BB

      // is "almost empty", we attempt to merge BB with its sole successor.

      auto *BI = dyn_cast<BranchInst>(BB.getTerminator());

      if (BI && BI->isUnconditional() &&

      if (BI && BI->isUnconditional()) {

        BasicBlock *Succ = BI->getSuccessor(0);

        if (

            // The terminator must be the only non-phi instruction in BB.

            BB.getFirstNonPHIOrDbg()->isTerminator() &&

            // Don't alter Loop headers and latches to ensure another pass can

            // detect and transform nested loops later.

          !LoopHeaders.count(&BB) && !LoopHeaders.count(BI->getSuccessor(0)) &&

            !LoopHeaders.count(&BB) && !LoopHeaders.count(Succ) &&

            TryToSimplifyUncondBranchFromEmptyBlock(&BB, DTU)) {

          RemoveRedundantDbgInstrs(Succ);

          // BB is valid for cleanup here because we passed in DTU. F remains

          // BB's parent until a DTU->getDomTree() event.

          LVI->eraseBlock(&BB);

          Changed = true;

        }

      }

    }

    EverChanged |= Changed;

  } while (Changed);

; RUN: opt -jump-threading -S < %s | FileCheck %s

define dso_local i32 @_Z3fooi(i32 %a) !dbg !7 {

entry:

  call void @llvm.dbg.value(metadata i32 %a, metadata !12, metadata !DIExpression()), !dbg !13

  call void @llvm.dbg.value(metadata i32 1, metadata !14, metadata !DIExpression()), !dbg !13

  %tobool = icmp ne i32 %a, 0, !dbg !15

  br i1 %tobool, label %if.then, label %if.end, !dbg !17

if.then:                                          ; preds = %entry

  call void @_Z4callv(), !dbg !18

  call void @llvm.dbg.value(metadata i32 0, metadata !14, metadata !DIExpression()), !dbg !13

  br label %if.end, !dbg !20

if.end:                                           ; preds = %if.then, %entry

  %c.0 = phi i32 [ 0, %if.then ], [ 1, %entry ], !dbg !13

  call void @llvm.dbg.value(metadata i32 %c.0, metadata !14, metadata !DIExpression()), !dbg !13

  %tobool1 = icmp ne i32 %c.0, 0, !dbg !21

  br i1 %tobool1, label %if.else, label %if.then2, !dbg !23

; CHECK-LABEL: if.then2:

; CHECK: call void @llvm.dbg.value({{.+}}, metadata ![[B:[0-9]+]], metadata !DIExpression())

; CHECK: call void @llvm.dbg.value({{.+}}, metadata ![[B:[0-9]+]], metadata !DIExpression())

; CHECK-NOT: call void @llvm.dbg.value({{.+}}, metadata ![[B]], metadata !DIExpression())

if.then2:                                         ; preds = %if.end

  call void @llvm.dbg.value(metadata i32 4, metadata !24, metadata !DIExpression()), !dbg !13

  br label %if.end3, !dbg !25

; CHECK-LABEL: if.end3:

if.else:                                          ; preds = %if.end

  call void @llvm.dbg.value(metadata i32 6, metadata !24, metadata !DIExpression()), !dbg !13

  br label %if.end3

if.end3:                                          ; preds = %if.else, %if.then2

  %b.0 = phi i32 [ 6, %if.else ], [ 4, %if.then2 ], !dbg !27

  call void @llvm.dbg.value(metadata i32 %b.0, metadata !24, metadata !DIExpression()), !dbg !13

  ret i32 %b.0, !dbg !28

}

; Function Attrs: nounwind readnone speculatable willreturn

declare void @llvm.dbg.declare(metadata, metadata, metadata)

declare dso_local void @_Z4callv()

; Function Attrs: nounwind readnone speculatable willreturn

declare void @llvm.dbg.value(metadata, metadata, metadata)

!llvm.dbg.cu = !{!0}

!llvm.module.flags = !{!3, !4, !5}

!llvm.ident = !{!6}

; CHECK: ![[B]] = !DILocalVariable(name: "b"

!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)

!1 = !DIFile(filename: "test.cpp", directory: "/")

!2 = !{}

!3 = !{i32 7, !"Dwarf Version", i32 4}

!4 = !{i32 2, !"Debug Info Version", i32 3}

!5 = !{i32 1, !"wchar_size", i32 4}

!6 = !{!"clang version 10.0.0"}

!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fooi", scope: !8, file: !8, line: 3, type: !9, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)

!8 = !DIFile(filename: "./test.cpp", directory: "/")

!9 = !DISubroutineType(types: !10)

!10 = !{!11, !11}

!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)

!12 = !DILocalVariable(name: "a", arg: 1, scope: !7, file: !8, line: 3, type: !11)

!13 = !DILocation(line: 0, scope: !7)

!14 = !DILocalVariable(name: "c", scope: !7, file: !8, line: 4, type: !11)

!15 = !DILocation(line: 5, column: 7, scope: !16)

!16 = distinct !DILexicalBlock(scope: !7, file: !8, line: 5, column: 7)

!17 = !DILocation(line: 5, column: 7, scope: !7)

!18 = !DILocation(line: 6, column: 5, scope: !19)

!19 = distinct !DILexicalBlock(scope: !16, file: !8, line: 5, column: 10)

!20 = !DILocation(line: 8, column: 3, scope: !19)

!21 = !DILocation(line: 9, column: 8, scope: !22)

!22 = distinct !DILexicalBlock(scope: !7, file: !8, line: 9, column: 7)

!23 = !DILocation(line: 9, column: 7, scope: !7)

!24 = !DILocalVariable(name: "b", scope: !7, file: !8, line: 4, type: !11)

!25 = !DILocation(line: 11, column: 3, scope: !26)

!26 = distinct !DILexicalBlock(scope: !22, file: !8, line: 9, column: 11)

!27 = !DILocation(line: 0, scope: !22)

!28 = !DILocation(line: 14, column: 3, scope: !7)