From 8a410bcef02c25b6b3a49fa6483875eb64539aad Mon Sep 17 00:00:00 2001
From: Erich Keane <erich.keane@intel.com>
Date: Mon, 7 Oct 2019 17:28:03 +0000
Subject: [PATCH] Fix Calling Convention through aliases

r369697 changed the behavior of stripPointerCasts to no longer include
aliases.  However, the code in CGDeclCXX.cpp's createAtExitStub counted
on the looking through aliases to properly set the calling convention of
a call.

The result of the change was that the calling convention mismatch of the
call would be replaced with a llvm.trap, causing a runtime crash.

Differential Revision: https://reviews.llvm.org/D68584

llvm-svn: 373929
---
 clang/lib/CodeGen/CGDeclCXX.cpp                |  4 ++--
 clang/test/CodeGenCXX/call-conv-thru-alias.cpp | 21 +++++++++++++++++++++
 llvm/include/llvm/IR/Value.h                   | 10 ++++++++++
 llvm/lib/IR/Value.cpp                          |  8 ++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/CodeGenCXX/call-conv-thru-alias.cpp

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index a54e5dc..bf16b7b 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -248,8 +248,8 @@ llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
 
  // Make sure the call and the callee agree on calling convention.
-  if (llvm::Function *dtorFn =
-          dyn_cast<llvm::Function>(dtor.getCallee()->stripPointerCasts()))
+  if (auto *dtorFn = dyn_cast<llvm::Function>(
+          dtor.getCallee()->stripPointerCastsAndAliases()))
     call->setCallingConv(dtorFn->getCallingConv());
 
   CGF.FinishFunction();
diff --git a/clang/test/CodeGenCXX/call-conv-thru-alias.cpp b/clang/test/CodeGenCXX/call-conv-thru-alias.cpp
new file mode 100644
index 0000000..5bd5c7d
--- /dev/null
+++ b/clang/test/CodeGenCXX/call-conv-thru-alias.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple i686-windows-pc -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-passes %s | FileCheck %s
+
+struct Base { virtual ~Base(); };
+struct Derived : Base {
+  virtual ~Derived();
+  static Derived inst;
+};
+
+Base::~Base(){}
+Derived::~Derived(){}
+Derived Derived::inst;
+
+// CHECK: @"??1Derived@@UAE@XZ" = dso_local unnamed_addr alias void (%struct.Derived*), bitcast (void (%struct.Base*)* @"??1Base@@UAE@XZ" to void (%struct.Derived*)*)
+
+// CHECK: define dso_local x86_thiscallcc void @"??1Base@@UAE@XZ"
+// CHECK: define internal void @"??__E?inst@Derived@@2U1@A@@YAXXZ"
+// CHECK: call i32 @atexit(void ()* @"??__F?inst@Derived@@2U1@A@@YAXXZ"
+//
+// CHECK: define internal void @"??__F?inst@Derived@@2U1@A@@YAXXZ"
+// CHECK-NEXT: entry:
+// CHECK-NEXT: call x86_thiscallcc void @"??1Derived@@UAE@XZ"
diff --git a/llvm/include/llvm/IR/Value.h b/llvm/include/llvm/IR/Value.h
index 03d2ce4..5850290 100644
--- a/llvm/include/llvm/IR/Value.h
+++ b/llvm/include/llvm/IR/Value.h
@@ -523,6 +523,16 @@ public:
         static_cast<const Value *>(this)->stripPointerCasts());
   }
 
+  /// Strip off pointer casts, all-zero GEPs, address space casts, and aliases.
+  ///
+  /// Returns the original uncasted value.  If this is called on a non-pointer
+  /// value, it returns 'this'.
+  const Value *stripPointerCastsAndAliases() const;
+  Value *stripPointerCastsAndAliases() {
+    return const_cast<Value *>(
+        static_cast<const Value *>(this)->stripPointerCastsAndAliases());
+  }
+
   /// Strip off pointer casts, all-zero GEPs and address space casts
   /// but ensures the representation of the result stays the same.
   ///
diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 65b98d3..c44d4b4 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -455,6 +455,7 @@ namespace {
 // Various metrics for how much to strip off of pointers.
 enum PointerStripKind {
   PSK_ZeroIndices,
+  PSK_ZeroIndicesAndAliases,
   PSK_ZeroIndicesSameRepresentation,
   PSK_ZeroIndicesAndInvariantGroups,
   PSK_InBoundsConstantIndices,
@@ -475,6 +476,7 @@ static const Value *stripPointerCastsAndOffsets(const Value *V) {
     if (auto *GEP = dyn_cast<GEPOperator>(V)) {
       switch (StripKind) {
       case PSK_ZeroIndices:
+      case PSK_ZeroIndicesAndAliases:
       case PSK_ZeroIndicesSameRepresentation:
       case PSK_ZeroIndicesAndInvariantGroups:
         if (!GEP->hasAllZeroIndices())
@@ -497,6 +499,8 @@ static const Value *stripPointerCastsAndOffsets(const Value *V) {
       // TODO: If we know an address space cast will not change the
       //       representation we could look through it here as well.
       V = cast<Operator>(V)->getOperand(0);
+    } else if (StripKind == PSK_ZeroIndicesAndAliases && isa<GlobalAlias>(V)) {
+      V = cast<GlobalAlias>(V)->getAliasee();
     } else {
       if (const auto *Call = dyn_cast<CallBase>(V)) {
         if (const Value *RV = Call->getReturnedArgOperand()) {
@@ -526,6 +530,10 @@ const Value *Value::stripPointerCasts() const {
   return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
 }
 
+const Value *Value::stripPointerCastsAndAliases() const {
+  return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
+}
+
 const Value *Value::stripPointerCastsSameRepresentation() const {
   return stripPointerCastsAndOffsets<PSK_ZeroIndicesSameRepresentation>(this);
 }
-- 
2.7.4