Add llvm.codeview.annotation to implement MSVC __annotation

Summary:
This intrinsic represents a label with a list of associated metadata
strings. It is modelled as reading and writing inaccessible memory so
that it won't be removed as dead code. I think the intention is that the
annotation strings should appear at most once in the debug info, so I
marked it noduplicate. We are allowed to inline code with annotations as
long as we strip the annotation, but that can be done later.

Reviewers: majnemer

Subscribers: eraman, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D36904

llvm-svn: 312569

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 218f8db9cde..e4084856272 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -860,6 +860,30 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
       emitInlinedCallSite(FI, InlinedAt, I->second);
     }
 
+    for (auto Annot : FI.Annotations) {
+      MCSymbol *Label = Annot.first;
+      MDTuple *Strs = cast<MDTuple>(Annot.second);
+      MCSymbol *AnnotBegin = MMI->getContext().createTempSymbol(),
+               *AnnotEnd = MMI->getContext().createTempSymbol();
+      OS.AddComment("Record length");
+      OS.emitAbsoluteSymbolDiff(AnnotEnd, AnnotBegin, 2);
+      OS.EmitLabel(AnnotBegin);
+      OS.AddComment("Record kind: S_ANNOTATION");
+      OS.EmitIntValue(SymbolKind::S_ANNOTATION, 2);
+      OS.EmitCOFFSecRel32(Label, /*Offset=*/0);
+      // FIXME: Make sure we don't overflow the max record size.
+      OS.EmitCOFFSectionIndex(Label);
+      OS.EmitIntValue(Strs->getNumOperands(), 2);
+      for (Metadata *MD : Strs->operands()) {
+        // MDStrings are null terminated, so we can do EmitBytes and get the
+        // nice .asciz directive.
+        StringRef Str = cast<MDString>(MD)->getString();
+        assert(Str.data()[Str.size()] == '\0' && "non-nullterminated MDString");
+        OS.EmitBytes(StringRef(Str.data(), Str.size() + 1));
+      }
+      OS.EmitLabel(AnnotEnd);
+    }
+
     if (SP != nullptr)
       emitDebugInfoForUDTs(LocalUDTs);
 
@@ -2195,6 +2219,8 @@ void CodeViewDebug::endFunctionImpl(const MachineFunction *MF) {
     return;
   }
 
+  CurFn->Annotations = MF->getCodeViewAnnotations();
+
   CurFn->End = Asm->getFunctionEnd();
 
   CurFn = nullptr;