[CodeView] Initial support for emitting S_THUNK32 symbols for compiler...
When emitting CodeView debug information, compiler-generated thunk routines
should be emitted using S_THUNK32 symbols instead of S_GPROC32_ID symbols so
Visual Studio can properly step into the user code. This initial support only
handles standard thunk ordinals.
Differential Revision: https://reviews.llvm.org/D43838
llvm-svn: 330132
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 6769ed4..a7bc8a8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -838,6 +838,57 @@
emitCodeViewMagicVersion();
}
+// Emit an S_THUNK32/S_END symbol pair for a thunk routine.
+// The only supported thunk ordinal is currently the standard type.
+void CodeViewDebug::emitDebugInfoForThunk(const Function *GV,
+ FunctionInfo &FI,
+ const MCSymbol *Fn) {
+ std::string FuncName = GlobalValue::dropLLVMManglingEscape(GV->getName());
+ const ThunkOrdinal ordinal = ThunkOrdinal::Standard; // Only supported kind.
+
+ OS.AddComment("Symbol subsection for " + Twine(FuncName));
+ MCSymbol *SymbolsEnd = beginCVSubsection(DebugSubsectionKind::Symbols);
+
+ // Emit S_THUNK32
+ MCSymbol *ThunkRecordBegin = MMI->getContext().createTempSymbol(),
+ *ThunkRecordEnd = MMI->getContext().createTempSymbol();
+ OS.AddComment("Record length");
+ OS.emitAbsoluteSymbolDiff(ThunkRecordEnd, ThunkRecordBegin, 2);
+ OS.EmitLabel(ThunkRecordBegin);
+ OS.AddComment("Record kind: S_THUNK32");
+ OS.EmitIntValue(unsigned(SymbolKind::S_THUNK32), 2);
+ OS.AddComment("PtrParent");
+ OS.EmitIntValue(0, 4);
+ OS.AddComment("PtrEnd");
+ OS.EmitIntValue(0, 4);
+ OS.AddComment("PtrNext");
+ OS.EmitIntValue(0, 4);
+ OS.AddComment("Thunk section relative address");
+ OS.EmitCOFFSecRel32(Fn, /*Offset=*/0);
+ OS.AddComment("Thunk section index");
+ OS.EmitCOFFSectionIndex(Fn);
+ OS.AddComment("Code size");
+ OS.emitAbsoluteSymbolDiff(FI.End, Fn, 2);
+ OS.AddComment("Ordinal");
+ OS.EmitIntValue(unsigned(ordinal), 1);
+ OS.AddComment("Function name");
+ emitNullTerminatedSymbolName(OS, FuncName);
+ // Additional fields specific to the thunk ordinal would go here.
+ OS.EmitLabel(ThunkRecordEnd);
+
+ // Local variables/inlined routines are purposely omitted here. The point of
+ // marking this as a thunk is so Visual Studio will NOT stop in this routine.
+
+ // Emit S_PROC_ID_END
+ const unsigned RecordLengthForSymbolEnd = 2;
+ OS.AddComment("Record length");
+ OS.EmitIntValue(RecordLengthForSymbolEnd, 2);
+ OS.AddComment("Record kind: S_PROC_ID_END");
+ OS.EmitIntValue(unsigned(SymbolKind::S_PROC_ID_END), 2);
+
+ endCVSubsection(SymbolsEnd);
+}
+
void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
FunctionInfo &FI) {
// For each function there is a separate subsection which holds the PC to
@@ -853,6 +904,11 @@
assert(SP);
setCurrentSubprogram(SP);
+ if (SP->isThunk()) {
+ emitDebugInfoForThunk(GV, FI, Fn);
+ return;
+ }
+
// If we have a display name, build the fully qualified name by walking the
// chain of scopes.
if (!SP->getName().empty())
@@ -2516,7 +2572,8 @@
ScopeVariables.clear();
// Don't emit anything if we don't have any line tables.
- if (!CurFn->HaveLineInfo) {
+ // Thunks are compiler-generated and probably won't have source correlation.
+ if (!CurFn->HaveLineInfo && !GV.getSubprogram()->isThunk()) {
FnDebugInfo.erase(&GV);
CurFn = nullptr;
return;
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index e58c4c6..e16c035 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -251,6 +251,10 @@
void emitInlineeLinesSubsection();
+ void emitDebugInfoForThunk(const Function *GV,
+ FunctionInfo &FI,
+ const MCSymbol *Fn);
+
void emitDebugInfoForFunction(const Function *GV, FunctionInfo &FI);
void emitDebugInfoForGlobals();