MS ABI: Use the correct this arg when generating implict copy ctor

We assumed that the incoming this argument would be the last argument.

However, this is not true under the MS ABI.

This fixes PR20897.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217642 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGCXXABI.h b/lib/CodeGen/CGCXXABI.h
index fe331795e91dab49c69e3e9ab9daac47c1b0530b..cf2cccd9910693b8f96bb8258dd15b54ffc6a67c 100644 (file)
--- a/lib/CodeGen/CGCXXABI.h
+++ b/lib/CodeGen/CGCXXABI.h
@@ -384,6 +384,9 @@ public:
   virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
                                    RValue RV, QualType ResultType);
 
+  virtual size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
+                                      FunctionArgList &Args) const = 0;
+
   /// Gets the pure virtual member call function.
   virtual StringRef GetPureVirtualCallName() = 0;
 

diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index 1de325feea388501315df69a3ed92f6bc2a802f6..72869d8ca9b3c4ff27125ff2d674c281634d8f89 100644 (file)
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -914,11 +914,12 @@ namespace {
   private:
 
     /// Get source argument for copy constructor. Returns null if not a copy
-    /// constructor. 
-    static const VarDecl* getTrivialCopySource(const CXXConstructorDecl *CD,
+    /// constructor.
+    static const VarDecl *getTrivialCopySource(CodeGenFunction &CGF,
+                                               const CXXConstructorDecl *CD,
                                                FunctionArgList &Args) {
       if (CD->isCopyOrMoveConstructor() && CD->isDefaulted())
-        return Args[Args.size() - 1];
+        return Args[CGF.CGM.getCXXABI().getSrcArgforCopyCtor(CD, Args)];
       return nullptr;
     }
 
@@ -949,7 +950,7 @@ namespace {
   public:
     ConstructorMemcpyizer(CodeGenFunction &CGF, const CXXConstructorDecl *CD,
                           FunctionArgList &Args)
-      : FieldMemcpyizer(CGF, CD->getParent(), getTrivialCopySource(CD, Args)),
+      : FieldMemcpyizer(CGF, CD->getParent(), getTrivialCopySource(CGF, CD, Args)),
         ConstructorDecl(CD),
         MemcpyableCtor(CD->isDefaulted() &&
                        CD->isCopyOrMoveConstructor() &&

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 25e2715daafce659bdbf245dae3a347812e28cf3..bcc0f166203a12daaec0d7a1645d9d1642c7ba4a 100644 (file)
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -208,6 +208,12 @@ public:
   llvm::Value *performReturnAdjustment(CodeGenFunction &CGF, llvm::Value *Ret,
                                        const ReturnAdjustment &RA) override;
 
+  size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
+                              FunctionArgList &Args) const override {
+    assert(!Args.empty() && "expected the arglist to not be empty!");
+    return Args.size() - 1;
+  }
+
   StringRef GetPureVirtualCallName() override { return "__cxa_pure_virtual"; }
   StringRef GetDeletedVirtualCallName() override
     { return "__cxa_deleted_virtual"; }

diff --git a/lib/CodeGen/MicrosoftCXXABI.cpp b/lib/CodeGen/MicrosoftCXXABI.cpp
index 173099a6bba7587f81949d852df7caab9cbebf6e..04b7ea08edc6630d07982b64b21b19a0107dbc85 100644 (file)
--- a/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -50,6 +50,18 @@ public:
 
   bool isSRetParameterAfterThis() const override { return true; }
 
+  size_t getSrcArgforCopyCtor(const CXXConstructorDecl *CD,
+                              FunctionArgList &Args) const override {
+    assert(Args.size() >= 2 &&
+           "expected the arglist to have at least two args!");
+    // The 'most_derived' parameter goes second if the ctor is variadic and
+    // has v-bases.
+    if (CD->getParent()->getNumVBases() > 0 &&
+        CD->getType()->castAs<FunctionProtoType>()->isVariadic())
+      return 2;
+    return 1;
+  }
+
   StringRef GetPureVirtualCallName() override { return "_purecall"; }
   // No known support for deleted functions in MSVC yet, so this choice is
   // arbitrary.

diff --git a/test/CodeGenCXX/pr20897.cpp b/test/CodeGenCXX/pr20897.cpp
new file mode 100644 (file)
index 0000000..06828c0
--- /dev/null
+++ b/test/CodeGenCXX/pr20897.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple i686-windows-msvc   -emit-llvm -std=c++1y -O0 -o - %s | FileCheck %s
+struct Base {};
+
+// __declspec(dllexport) causes us to export the implicit constructor.
+struct __declspec(dllexport) Derived : virtual Base {
+// CHECK-LABEL: define weak_odr dllexport x86_thiscallcc %struct.Derived* @"\01??0Derived@@QAE@ABU0@@Z"
+// CHECK:      %[[this:.*]] = load %struct.Derived** {{.*}}
+// CHECK-NEXT: store %struct.Derived* %[[this]], %struct.Derived** %[[retval:.*]]
+// CHECK:      %[[dest_a_gep:.*]] = getelementptr inbounds %struct.Derived* %[[this]], i32 0, i32 1
+// CHECK-NEXT: %[[src_load:.*]]   = load %struct.Derived** {{.*}}
+// CHECK-NEXT: %[[src_a_gep:.*]]  = getelementptr inbounds %struct.Derived* %[[src_load:.*]], i32 0, i32 1
+// CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %[[dest_a_gep]], i8* %[[src_a_gep]], i64 1, i32 4, i1 false)
+// CHECK-NEXT: %[[dest_this:.*]] = load %struct.Derived** %[[retval]]
+// CHECK-NEXT: ret %struct.Derived* %[[dest_this]]
+  bool a : 1;
+  bool b : 1;
+};