XCore target: fix bug in dereferencing null pointer.

[robertlytton]

Summary

The code only affects XCore targets.
The 'const VarDecl *D' was not being checked for null prior to dereferencing.
This was discovered whilst compiling a empty destructor.

Also add testing of cpp ABI output where it differs from C ABI output.

[• friedgold]

LGTM

test/CodeGen/xcore-abi.cpp

17

This comment could be made clearer. What was the actual bug? Did it crash when emitting the destructor or did it crash because of an implicitly generated method?

lib/CodeGen/CodeGenModule.cpp

         D->isStaticDataMember() && D->hasInit() &&
         !D->isThisDeclarationADefinition())
       EmitGlobalVarDefinition(D);
+
+    // Handle XCore specific ABI requirements.
+    if (getTarget().getTriple().getArch() == llvm::Triple::xcore &&
+        D->getLanguageLinkage() == CLanguageLinkage &&
+        D->getType().isConstant(Context) &&
+        isExternallyVisible(LV.getLinkage()))
+      GV->setSection(".cp.rodata");
   }
 
   if (AddrSpace != Ty->getAddressSpace())
     return llvm::ConstantExpr::getAddrSpaceCast(GV, Ty);
 
-  if (getTarget().getTriple().getArch() == llvm::Triple::xcore &&
-      D->getLanguageLinkage() == CLanguageLinkage &&
-      D->getType().isConstant(Context) &&
-      isExternallyVisible(D->getLinkageAndVisibility().getLinkage()))
-    GV->setSection(".cp.rodata");
-
   getTargetCodeGenInfo().emitTargetMD(D, GV, *this);
 
   return GV;

test/CodeGen/xcore-abi.cpp

+// REQUIRES: xcore-registered-target
+
+// RUN: %clang_cc1 -triple xcore-unknown-unknown -fno-signed-char -fno-common -emit-llvm -o - -x c++ %s | FileCheck %s
+
+// CHECK: target triple = "xcore-unknown-unknown"
+
+
+// C++ constants are not placed into the ".cp.rodata" section.
+// CHECK: @cgx = external constant i32
+extern const int cgx;
+int fcgx() { return cgx;}
+// CHECK: @g1 = global i32 0, align 4
+int g1;
+// CHECK: @cg1 = constant i32 0, align 4
+extern const int cg1 = 0;
+
+// Make sure null 'VarDecl*' are not indirected.
+class C {
+public:
+  ~C(){};
+};
+C c;
+
+// CHECK: "no-frame-pointer-elim"="false"
+// CHECK-NOT: "no-frame-pointer-elim-non-leaf"