MS ABI: Return sret parameters when using inalloca

Previously the X86 backend would look for the sret attribute and handle
this for us.  inalloca takes that all away, so we have to do the return
ourselves now.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202097 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/CodeGen/CGFunctionInfo.h b/include/clang/CodeGen/CGFunctionInfo.h
index cb8c5a01182b2397c6f99bf0303ae6057927b9cf..ec41e8bdec2534291a3617b20ad2b20b1035c5d7 100644 (file)
--- a/include/clang/CodeGen/CGFunctionInfo.h
+++ b/include/clang/CodeGen/CGFunctionInfo.h
@@ -191,6 +191,18 @@ public:
     return UIntData;
   }
 
+  /// \brief Return true if this field of an inalloca struct should be returned
+  /// to implement a struct return calling convention.
+  bool getInAllocaSRet() const {
+    assert(TheKind == InAlloca && "Invalid kind!");
+    return BoolData0;
+  }
+
+  void setInAllocaSRet(bool SRet) {
+    assert(TheKind == InAlloca && "Invalid kind!");
+    BoolData0 = SRet;
+  }
+
   void dump() const;
 };
 

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index a21e4783b60b26376a2c3950c69e331ffda01e79..756b0b2b605c75f9cc89749436ad2851bab8cc94 100644 (file)
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -940,7 +940,15 @@ CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI) {
     break;
 
   case ABIArgInfo::InAlloca:
-    resultType = llvm::Type::getVoidTy(getLLVMContext());
+    if (retAI.getInAllocaSRet()) {
+      // sret things on win32 aren't void, they return the sret pointer.
+      QualType ret = FI.getReturnType();
+      llvm::Type *ty = ConvertType(ret);
+      unsigned addressSpace = Context.getTargetAddressSpace(ret);
+      resultType = llvm::PointerType::get(ty, addressSpace);
+    } else {
+      resultType = llvm::Type::getVoidTy(getLLVMContext());
+    }
     break;
 
   case ABIArgInfo::Indirect: {
@@ -1779,7 +1787,17 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
 
   switch (RetAI.getKind()) {
   case ABIArgInfo::InAlloca:
-    // Do nothing; aggregrates get evaluated directly into the destination.
+    // Aggregrates get evaluated directly into the destination.  Sometimes we
+    // need to return the sret value in a register, though.
+    assert(hasAggregateEvaluationKind(RetTy));
+    if (RetAI.getInAllocaSRet()) {
+      llvm::Function::arg_iterator EI = CurFn->arg_end();
+      --EI;
+      llvm::Value *ArgStruct = EI;
+      llvm::Value *SRet =
+          Builder.CreateStructGEP(ArgStruct, RetAI.getInAllocaFieldIndex());
+      RV = Builder.CreateLoad(SRet, "sret");
+    }
     break;
 
   case ABIArgInfo::Indirect: {

diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 05cb21dd1905dd7271323501e9f8cf092a467dad..e1c586a7d287be33d99d6623f11612a795c8bf1d 100644 (file)
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -1061,6 +1061,8 @@ void X86_32ABIInfo::rewriteWithInAlloca(CGFunctionInfo &FI) const {
   if (Ret.isIndirect() && !Ret.getInReg()) {
     CanQualType PtrTy = getContext().getPointerType(FI.getReturnType());
     addFieldToArgStruct(FrameFields, StackOffset, Ret, PtrTy);
+    // On Windows, the hidden sret parameter is always returned in eax.
+    Ret.setInAllocaSRet(IsWin32StructABI);
   }
 
   // Skip the 'this' parameter in ecx.

diff --git a/test/CodeGenCXX/microsoft-abi-byval-sret.cpp b/test/CodeGenCXX/microsoft-abi-byval-sret.cpp
index 00d36b7d492442792858492fe2ed7e579137770c..985b1ce62e924d80637d5c0360bb948b23f0a733 100644 (file)
--- a/test/CodeGenCXX/microsoft-abi-byval-sret.cpp
+++ b/test/CodeGenCXX/microsoft-abi-byval-sret.cpp
@@ -14,13 +14,16 @@ A A::foo(A x) {
   return y;
 }
 
-// CHECK: define x86_thiscallcc void @"\01?foo@A@@QAE?AU1@U1@@Z"
+// CHECK-LABEL: define x86_thiscallcc %struct.A* @"\01?foo@A@@QAE?AU1@U1@@Z"
 // CHECK:       (%struct.A* %this, <{ %struct.A*, %struct.A }>* inalloca)
+// CHECK:   getelementptr inbounds <{ %struct.A*, %struct.A }>* %{{.*}}, i32 0, i32 0
+// CHECK:   load %struct.A**
+// CHECK:   ret %struct.A*
 
 int main() {
   A x;
   A y = x.foo(x);
 }
 
-// CHECK: call x86_thiscallcc void @"\01?foo@A@@QAE?AU1@U1@@Z"
+// CHECK: call x86_thiscallcc %struct.A* @"\01?foo@A@@QAE?AU1@U1@@Z"
 // CHECK:       (%struct.A* %{{[^,]*}}, <{ %struct.A*, %struct.A }>* inalloca %{{[^,]*}})