Update the linkage name of coro-split functions in the debug info.

This patch updates the linkage name in the DISubprogram of coro-split
functions, which is particularly important for Swift, where the
funclets have a special name mangling. This patch does not affect C++
coroutines, since the DW_AT_specification is expected to hold the
(original) linkage name. I believe this is mostly due to limitations
in AsmPrinter, so we might be able to relax this restriction in the
future.

Differential Revision: https://reviews.llvm.org/D99693

Author: adrian-prantl

llvm/include/llvm/IR/DebugInfoMetadata.h

@@ -2010,6 +2010,8 @@ class DISubprogram : public DILocalScope {
 
   StringRef getName() const { return getStringOperand(2); }
   StringRef getLinkageName() const { return getStringOperand(3); }
+  /// Only used by clients of CloneFunction, and only right after the cloning.
+  void replaceLinkageName(MDString *LN) { replaceOperandWith(3, LN); }
 
   DISubroutineType *getType() const {
     return cast_or_null<DISubroutineType>(getRawType());

llvm/lib/Transforms/Coroutines/CoroSplit.cpp

@@ -846,6 +846,9 @@ void CoroCloner::create() {
 
   CloneFunctionInto(NewF, &OrigF, VMap,
                     CloneFunctionChangeType::LocalChangesOnly, Returns);
+
+  auto &Context = NewF->getContext();
+
   // For async functions / continuations, adjust the scope line of the
   // clone to the line number of the suspend point. The scope line is
   // associated with all pre-prologue instructions. This avoids a jump
@@ -855,15 +858,24 @@ void CoroCloner::create() {
     if (ActiveSuspend)
       if (auto DL = ActiveSuspend->getDebugLoc())
         SP->setScopeLine(DL->getLine());
+    // Update the linkage name to reflect the modified symbol name. It
+    // is necessary to update the linkage name in Swift, since the
+    // mangling changes for resume functions. It might also be the
+    // right thing to do in C++, but due to a limitation in LLVM's
+    // AsmPrinter we can only do this if the function doesn't have an
+    // abstract specification, since the DWARF backend expects the
+    // abstract specification to contain the linkage name and asserts
+    // that they are identical.
+    if (!SP->getDeclaration() && SP->getUnit() &&
+        SP->getUnit()->getSourceLanguage() == dwarf::DW_LANG_Swift)
+      SP->replaceLinkageName(MDString::get(Context, NewF->getName()));
   }
 
   NewF->setLinkage(savedLinkage);
   NewF->setVisibility(savedVisibility);
   NewF->setUnnamedAddr(savedUnnamedAddr);
   NewF->setDLLStorageClass(savedDLLStorageClass);
 
-  auto &Context = NewF->getContext();
-
   // Replace the attributes of the new function:
   auto OrigAttrs = NewF->getAttributes();
   auto NewAttrs = AttributeList();

llvm/test/Transforms/Coroutines/coro-async.ll

@@ -547,7 +547,7 @@ declare void @llvm.coro.async.size.replace(i8*, i8*)
                             scope: !2, file: !3, line: 1, type: !4,
                             scopeLine: 1, spFlags: DISPFlagDefinition, unit: !2)
 ; CHECK: ![[SP2]] = distinct !DISubprogram(name: "my_async_function",
-; CHECK-SAME:                              linkageName: "my_async_function",
+; CHECK-SAME:                              linkageName: "my_async_function.resume.0",
 ; CHECK-SAME:                              scopeLine: 2
 !2 = distinct !DICompileUnit(language: DW_LANG_Swift, file: !3, emissionKind: FullDebug)
 !3 = !DIFile(filename: "/tmp/1.swift", directory: "/")

llvm/test/Transforms/Coroutines/coro-debug.ll

@@ -114,7 +114,7 @@ attributes #7 = { noduplicate }
 !3 = !{i32 2, !"Dwarf Version", i32 4}
 !4 = !{i32 2, !"Debug Info Version", i32 3}
 !5 = !{!"clang version 5.0.0"}
-!6 = distinct !DISubprogram(name: "f", linkageName: "flink", scope: !7, file: !7, line: 55, type: !8, isLocal: false, isDefinition: true, scopeLine: 55, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!6 = distinct !DISubprogram(name: "f", linkageName: "flink", scope: !7, file: !7, line: 55, type: !8, isLocal: false, isDefinition: true, scopeLine: 55, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2, declaration: !DISubprogram(name: "f", linkageName: "flink", scope: !7, file: !7, line: 55, type: !8, isLocal: false, isDefinition: false, flags: DIFlagPrototyped))
 !7 = !DIFile(filename: "simple-repro.c", directory: "C:\5CGitHub\5Cllvm\5Cbuild\5CDebug\5Cbin")
 !8 = !DISubroutineType(types: !9)
 !9 = !{!10, !11}