Index: llvm/trunk/lib/Transforms/Coroutines/CoroFrame.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Coroutines/CoroFrame.cpp
+++ llvm/trunk/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/circular_raw_ostream.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
 
 using namespace llvm;
 
@@ -637,6 +638,10 @@
 }
 
 void coro::buildCoroutineFrame(Function &F, Shape &Shape) {
+  // Lower coro.dbg.declare to coro.dbg.value, since we are going to rewrite
+  // access to local variables.
+  LowerDbgDeclare(F);
+
   Shape.PromiseAlloca = Shape.CoroBegin->getId()->getPromise();
   if (Shape.PromiseAlloca) {
     Shape.CoroBegin->getId()->clearPromise();
Index: llvm/trunk/lib/Transforms/Coroutines/CoroSplit.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Coroutines/CoroSplit.cpp
+++ llvm/trunk/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -200,14 +200,16 @@
 
   SmallVector<ReturnInst *, 4> Returns;
 
+  if (DISubprogram *SP = F.getSubprogram()) {
+    // If we have debug info, add mapping for the metadata nodes that should not
+    // be cloned by CloneFunctionInfo.
+    auto &MD = VMap.MD();
+    MD[SP->getUnit()].reset(SP->getUnit());
+    MD[SP->getType()].reset(SP->getType());
+    MD[SP->getFile()].reset(SP->getFile());
+  }
   CloneFunctionInto(NewF, &F, VMap, /*ModuleLevelChanges=*/true, Returns);
 
-  // If we have debug info, update it. ModuleLevelChanges = true above, does
-  // the heavy lifting, we just need to repoint subprogram at the same
-  // DICompileUnit as the original function F.
-  if (DISubprogram *SP = F.getSubprogram())
-    NewF->getSubprogram()->replaceUnit(SP->getUnit());
-
   // Remove old returns.
   for (ReturnInst *Return : Returns)
     changeToUnreachable(Return, /*UseLLVMTrap=*/false);
Index: llvm/trunk/test/Transforms/Coroutines/coro-split-dbg.ll
===================================================================
--- llvm/trunk/test/Transforms/Coroutines/coro-split-dbg.ll
+++ llvm/trunk/test/Transforms/Coroutines/coro-split-dbg.ll
@@ -0,0 +1,119 @@
+; Make sure that coro-split correctly deals with debug information.
+; The test here is simply that it does not result in bad IR that will crash opt.
+; RUN: opt < %s -coro-split -disable-output
+source_filename = "coro.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+declare void @bar(...) local_unnamed_addr #2
+
+; Function Attrs: nounwind uwtable
+define i8* @f() #3 !dbg !16 {
+entry:
+  %0 = tail call token @llvm.coro.id(i32 0, i8* null, i8* bitcast (i8* ()* @f to i8*), i8* null), !dbg !26
+  %1 = tail call i64 @llvm.coro.size.i64(), !dbg !26
+  %call = tail call i8* @malloc(i64 %1), !dbg !26
+  %2 = tail call i8* @llvm.coro.begin(token %0, i8* %call) #9, !dbg !26
+  tail call void @llvm.dbg.value(metadata i8* %2, i64 0, metadata !21, metadata !12), !dbg !26
+  br label %for.cond, !dbg !27
+
+for.cond:                                         ; preds = %for.cond, %entry
+  tail call void @llvm.dbg.value(metadata i32 undef, i64 0, metadata !22, metadata !12), !dbg !28
+  tail call void @llvm.dbg.value(metadata i32 undef, i64 0, metadata !11, metadata !12) #7, !dbg !29
+  tail call void (...) @bar() #7, !dbg !33
+  %3 = tail call token @llvm.coro.save(i8* null), !dbg !34
+  %4 = tail call i8 @llvm.coro.suspend(token %3, i1 false), !dbg !34
+  %conv = sext i8 %4 to i32, !dbg !34
+  switch i32 %conv, label %coro_Suspend [
+    i32 0, label %for.cond
+    i32 1, label %coro_Cleanup
+  ], !dbg !34
+
+coro_Cleanup:                                     ; preds = %for.cond
+  %5 = tail call i8* @llvm.coro.free(token %0, i8* %2), !dbg !35
+  tail call void @free(i8* nonnull %5), !dbg !36
+  br label %coro_Suspend, !dbg !36
+
+coro_Suspend:                                     ; preds = %for.cond, %if.then, %coro_Cleanup
+  tail call void @llvm.coro.end(i8* null, i1 false) #9, !dbg !38
+  ret i8* %2, !dbg !39
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start(i64, i8* nocapture) #4
+
+; Function Attrs: argmemonly nounwind readonly
+declare token @llvm.coro.id(i32, i8* readnone, i8* nocapture readonly, i8*) #5
+
+; Function Attrs: nounwind
+declare noalias i8* @malloc(i64) local_unnamed_addr #6
+declare i64 @llvm.coro.size.i64() #1
+declare i8* @llvm.coro.begin(token, i8* writeonly) #7
+declare token @llvm.coro.save(i8*) #7
+declare i8 @llvm.coro.suspend(token, i1) #7
+declare void @llvm.lifetime.end(i64, i8* nocapture) #4
+declare i8* @llvm.coro.free(token, i8* nocapture readonly) #5
+declare void @free(i8* nocapture) local_unnamed_addr #6
+declare void @llvm.coro.end(i8*, i1) #7
+declare i8* @llvm.coro.subfn.addr(i8* nocapture readonly, i8) #5
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #3 = { nounwind uwtable "coroutine.presplit"="1" "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #4 = { argmemonly nounwind }
+attributes #5 = { argmemonly nounwind readonly }
+attributes #6 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #7 = { nounwind }
+attributes #8 = { alwaysinline nounwind }
+attributes #9 = { noduplicate }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (http://llvm.org/git/clang.git 6c405f93921ac99ff5b8521bb1b3df4449deede4) (http://llvm.org/git/llvm.git 6e6d3247102a0f87ce14e906dcf6a3a5ed3faa65)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "coro.c", directory: "/home/gor/build/bin")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!"clang version 4.0.0 (http://llvm.org/git/clang.git 6c405f93921ac99ff5b8521bb1b3df4449deede4) (http://llvm.org/git/llvm.git 6e6d3247102a0f87ce14e906dcf6a3a5ed3faa65)"}
+!6 = distinct !DISubprogram(name: "print", scope: !1, file: !1, line: 6, type: !7, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !10)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null, !9}
+!9 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!10 = !{!11}
+!11 = !DILocalVariable(name: "v", arg: 1, scope: !6, file: !1, line: 6, type: !9)
+!12 = !DIExpression()
+!13 = !DILocation(line: 6, column: 16, scope: !6)
+!14 = !DILocation(line: 6, column: 19, scope: !6)
+!15 = !DILocation(line: 6, column: 25, scope: !6)
+!16 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 8, type: !17, isLocal: false, isDefinition: true, scopeLine: 8, isOptimized: true, unit: !0, variables: !20)
+!17 = !DISubroutineType(types: !18)
+!18 = !{!19}
+!19 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64, align: 64)
+!20 = !{!21, !22, !24}
+!21 = !DILocalVariable(name: "coro_hdl", scope: !16, file: !1, line: 9, type: !19)
+!22 = !DILocalVariable(name: "i", scope: !23, file: !1, line: 11, type: !9)
+!23 = distinct !DILexicalBlock(scope: !16, file: !1, line: 11, column: 3)
+!24 = !DILocalVariable(name: "coro_mem", scope: !25, file: !1, line: 16, type: !19)
+!25 = distinct !DILexicalBlock(scope: !16, file: !1, line: 16, column: 3)
+!26 = !DILocation(line: 9, column: 3, scope: !16)
+!27 = !DILocation(line: 11, column: 8, scope: !23)
+!28 = !DILocation(line: 11, column: 12, scope: !23)
+!29 = !DILocation(line: 6, column: 16, scope: !6, inlinedAt: !30)
+!30 = distinct !DILocation(line: 12, column: 5, scope: !31)
+!31 = distinct !DILexicalBlock(scope: !32, file: !1, line: 11, column: 25)
+!32 = distinct !DILexicalBlock(scope: !23, file: !1, line: 11, column: 3)
+!33 = !DILocation(line: 6, column: 19, scope: !6, inlinedAt: !30)
+!34 = !DILocation(line: 13, column: 5, scope: !31)
+!35 = !DILocation(line: 16, column: 3, scope: !25)
+!36 = !DILocation(line: 16, column: 3, scope: !37)
+!37 = distinct !DILexicalBlock(scope: !25, file: !1, line: 16, column: 3)
+!38 = !DILocation(line: 16, column: 3, scope: !16)
+!39 = !DILocation(line: 17, column: 1, scope: !16)