Reland "[codegen] Store address of indirect arguments on the stack"

The commit was reverted due to a regression in debug information of an
optimized code test in lldb. This has since been addressed by:

1. rGf753e5be8239: [LiveDebugValues] Allow EntryValue with OP_deref
expressions
2. rG055f2f04e658: [mem2reg][debuginfo] Handle op_deref when converting
dbg.declare

Differential Revision: https://reviews.llvm.org/D141381

3 files changed, 22 insertions, 7 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index fafc0f8..bb91b51 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -4840,9 +4840,10 @@ void CGDebugInfo::EmitDeclareOfBlockDeclRefVariable(
 
 llvm::DILocalVariable *
 CGDebugInfo::EmitDeclareOfArgVariable(const VarDecl *VD, llvm::Value *AI,
-                                      unsigned ArgNo, CGBuilderTy &Builder) {
+                                      unsigned ArgNo, CGBuilderTy &Builder,
+                                      bool UsePointerValue) {
   assert(CGM.getCodeGenOpts().hasReducedDebugInfo());
-  return EmitDeclare(VD, AI, ArgNo, Builder);
+  return EmitDeclare(VD, AI, ArgNo, Builder, UsePointerValue);
 }
 
 namespace {
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index d807fb7..a70b72e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -489,10 +489,9 @@ public:
 
   /// Emit call to \c llvm.dbg.declare for an argument variable
   /// declaration.
-  llvm::DILocalVariable *EmitDeclareOfArgVariable(const VarDecl *Decl,
-                                                  llvm::Value *AI,
-                                                  unsigned ArgNo,
-                                                  CGBuilderTy &Builder);
+  llvm::DILocalVariable *
+  EmitDeclareOfArgVariable(const VarDecl *Decl, llvm::Value *AI, unsigned ArgNo,
+                           CGBuilderTy &Builder, bool UsePointerValue = false);
 
   /// Emit call to \c llvm.dbg.declare for the block-literal argument
   /// to a block invocation function.
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index ceaddc4..a70997f 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -2476,6 +2476,8 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
   Address AllocaPtr = Address::invalid();
   bool DoStore = false;
   bool IsScalar = hasScalarEvaluationKind(Ty);
+  bool UseIndirectDebugAddress = false;
+
   // If we already have a pointer to the argument, reuse the input pointer.
   if (Arg.isIndirect()) {
     // If we have a prettier pointer type at this point, bitcast to that.
@@ -2487,6 +2489,19 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
     auto AllocaAS = CGM.getASTAllocaAddressSpace();
     auto *V = DeclPtr.getPointer();
     AllocaPtr = DeclPtr;
+
+    // For truly ABI indirect arguments -- those that are not `byval` -- store
+    // the address of the argument on the stack to preserve debug information.
+    ABIArgInfo ArgInfo = CurFnInfo->arguments()[ArgNo - 1].info;
+    if (ArgInfo.isIndirect())
+      UseIndirectDebugAddress = !ArgInfo.getIndirectByVal();
+    if (UseIndirectDebugAddress) {
+      auto PtrTy = getContext().getPointerType(Ty);
+      AllocaPtr = CreateMemTemp(PtrTy, getContext().getTypeAlignInChars(PtrTy),
+                                D.getName() + ".indirect_addr");
+      EmitStoreOfScalar(V, AllocaPtr, /* Volatile */ false, PtrTy);
+    }
+
     auto SrcLangAS = getLangOpts().OpenCL ? LangAS::opencl_private : AllocaAS;
     auto DestLangAS =
         getLangOpts().OpenCL ? LangAS::opencl_private : LangAS::Default;
@@ -2603,7 +2618,7 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
     if (CGM.getCodeGenOpts().hasReducedDebugInfo() && !CurFuncIsThunk &&
         !NoDebugInfo) {
       llvm::DILocalVariable *DILocalVar = DI->EmitDeclareOfArgVariable(
-          &D, AllocaPtr.getPointer(), ArgNo, Builder);
+          &D, AllocaPtr.getPointer(), ArgNo, Builder, UseIndirectDebugAddress);
       if (const auto *Var = dyn_cast_or_null<ParmVarDecl>(&D))
         DI->getParamDbgMappings().insert({Var, DILocalVar});
     }