Store a pointer to the return value in a static alloca and let the debugger use that
as the variable address for NRVO variables.
Subscribers: hiraditya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D63361
llvm-svn: 363952
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index a53ca8f..dbe582c 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3835,7 +3835,8 @@
llvm::DILocalVariable *CGDebugInfo::EmitDeclare(const VarDecl *VD,
llvm::Value *Storage,
llvm::Optional<unsigned> ArgNo,
- CGBuilderTy &Builder) {
+ CGBuilderTy &Builder,
+ const bool UsePointerValue) {
assert(DebugKind >= codegenoptions::LimitedDebugInfo);
assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
if (VD->hasAttr<NoDebugAttr>())
@@ -3940,6 +3941,16 @@
}
}
+ // Clang stores the sret pointer provided by the caller in a static alloca.
+ // Use DW_OP_deref to tell the debugger to load the pointer and treat it as
+ // the address of the variable.
+ if (UsePointerValue) {
+ assert(std::find(Expr.begin(), Expr.end(), llvm::dwarf::DW_OP_deref) ==
+ Expr.end() &&
+ "Debug info already contains DW_OP_deref.");
+ Expr.push_back(llvm::dwarf::DW_OP_deref);
+ }
+
// Create the descriptor for the variable.
auto *D = ArgNo ? DBuilder.createParameterVariable(
Scope, Name, *ArgNo, Unit, Line, Ty,
@@ -3958,9 +3969,10 @@
llvm::DILocalVariable *
CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD, llvm::Value *Storage,
- CGBuilderTy &Builder) {
+ CGBuilderTy &Builder,
+ const bool UsePointerValue) {
assert(DebugKind >= codegenoptions::LimitedDebugInfo);
- return EmitDeclare(VD, Storage, llvm::None, Builder);
+ return EmitDeclare(VD, Storage, llvm::None, Builder, UsePointerValue);
}
void CGDebugInfo::EmitLabel(const LabelDecl *D, CGBuilderTy &Builder) {
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index 054df01..f0c67cd 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -422,9 +422,10 @@
/// declaration.
/// Returns a pointer to the DILocalVariable associated with the
/// llvm.dbg.declare, or nullptr otherwise.
- llvm::DILocalVariable *EmitDeclareOfAutoVariable(const VarDecl *Decl,
- llvm::Value *AI,
- CGBuilderTy &Builder);
+ llvm::DILocalVariable *
+ EmitDeclareOfAutoVariable(const VarDecl *Decl, llvm::Value *AI,
+ CGBuilderTy &Builder,
+ const bool UsePointerValue = false);
/// Emit call to \c llvm.dbg.label for an label.
void EmitLabel(const LabelDecl *D, CGBuilderTy &Builder);
@@ -507,7 +508,8 @@
/// llvm.dbg.declare, or nullptr otherwise.
llvm::DILocalVariable *EmitDeclare(const VarDecl *decl, llvm::Value *AI,
llvm::Optional<unsigned> ArgNo,
- CGBuilderTy &Builder);
+ CGBuilderTy &Builder,
+ const bool UsePointerValue = false);
struct BlockByRefType {
/// The wrapper struct used inside the __block_literal struct.
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 233212c..c4e0d89 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -1403,12 +1403,11 @@
getLangOpts().OpenMP
? CGM.getOpenMPRuntime().getAddressOfLocalVariable(*this, &D)
: Address::invalid();
+ bool NRVO = getLangOpts().ElideConstructors && D.isNRVOVariable();
+
if (getLangOpts().OpenMP && OpenMPLocalAddr.isValid()) {
address = OpenMPLocalAddr;
} else if (Ty->isConstantSizeType()) {
- bool NRVO = getLangOpts().ElideConstructors &&
- D.isNRVOVariable();
-
// If this value is an array or struct with a statically determinable
// constant initializer, there are optimizations we can do.
//
@@ -1561,8 +1560,16 @@
// Emit debug info for local var declaration.
if (EmitDebugInfo && HaveInsertPoint()) {
+ Address DebugAddr = address;
+ bool UsePointerValue = NRVO && ReturnValuePointer.isValid();
DI->setLocation(D.getLocation());
- (void)DI->EmitDeclareOfAutoVariable(&D, address.getPointer(), Builder);
+
+ // If NRVO, use a pointer to the return address.
+ if (UsePointerValue)
+ DebugAddr = ReturnValuePointer;
+
+ (void)DI->EmitDeclareOfAutoVariable(&D, DebugAddr.getPointer(), Builder,
+ UsePointerValue);
}
if (D.hasAttr<AnnotateAttr>() && HaveInsertPoint())
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index b9573f7..581bbe5 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -895,6 +895,13 @@
if (CurFnInfo->getReturnInfo().isSRetAfterThis())
++AI;
ReturnValue = Address(&*AI, CurFnInfo->getReturnInfo().getIndirectAlign());
+ if (!CurFnInfo->getReturnInfo().getIndirectByVal()) {
+ ReturnValuePointer =
+ CreateDefaultAlignTempAlloca(Int8PtrTy, "result.ptr");
+ Builder.CreateStore(Builder.CreatePointerBitCastOrAddrSpaceCast(
+ ReturnValue.getPointer(), Int8PtrTy),
+ ReturnValuePointer);
+ }
} else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::InAlloca &&
!hasScalarEvaluationKind(CurFnInfo->getReturnType())) {
// Load the sret pointer from the argument struct and return into that.
@@ -902,6 +909,7 @@
llvm::Function::arg_iterator EI = CurFn->arg_end();
--EI;
llvm::Value *Addr = Builder.CreateStructGEP(nullptr, &*EI, Idx);
+ ReturnValuePointer = Address(Addr, getPointerAlign());
Addr = Builder.CreateAlignedLoad(Addr, getPointerAlign(), "agg.result");
ReturnValue = Address(Addr, getNaturalTypeAlignment(RetTy));
} else {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index b274f45..e95a07c 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -327,6 +327,10 @@
/// value. This is invalid iff the function has no return value.
Address ReturnValue = Address::invalid();
+ /// ReturnValuePointer - The temporary alloca to hold a pointer to sret.
+ /// This is invalid if sret is not in use.
+ Address ReturnValuePointer = Address::invalid();
+
/// Return true if a label was seen in the current scope.
bool hasLabelBeenSeenInCurrentScope() const {
if (CurLexicalScope)