Add nonnull in CodeGen for __attribute__((nonnull))

[hfinkel]

Summary

We now have an LLVM-level nonnull attribute that can be applied to function parameters, and we emit it for reference types (as of r209723), but we don't yet emit it when a attribute((nonnull)) is provided. This patch adds support for turning attribute((nonnull)) on the source level into nonnull at the IR level.

[hfinkel]

(it would be really nice to have an "Accept and Close" option).

[hfinkel]

Committed r212835.

lib/CodeGen/CGCall.cpp

if (RetAI.isIndirect()) {
     AI->addAttr(llvm::AttributeSet::get(getLLVMContext(), AI->getArgNo() + 1,
                                         llvm::Attribute::NoAlias));
     if (SwapThisWithSRet)
       --AI;  // Go back to the beginning for 'this'.
     else
       ++AI;  // Skip the sret parameter.
   }
 
+  // Get the function-level nonnull attribute if it exists.
+  const NonNullAttr *NNAtt =
+    CurCodeDecl ? CurCodeDecl->getAttr<NonNullAttr>() : nullptr;
+
   // Track if we received the parameter as a pointer (indirect, byval, or
   // inalloca).  If already have a pointer, EmitParmDecl doesn't need to copy it
   // into a local alloca for us.
   enum ValOrPointer { HaveValue = 0, HavePointer = 1 };
   typedef llvm::PointerIntPair<llvm::Value *, 1> ValueAndIsPtr;
   SmallVector<ValueAndIsPtr, 16> ArgVals;
   ArgVals.reserve(Args.size());
 
case ABIArgInfo::Direct: {
 
       // If we have the trivial case, handle it with no muss and fuss.
       if (!isa<llvm::StructType>(ArgI.getCoerceToType()) &&
           ArgI.getCoerceToType() == ConvertType(Ty) &&
           ArgI.getDirectOffset() == 0) {
         assert(AI != Fn->arg_end() && "Argument mismatch!");
         llvm::Value *V = AI;
 
+        if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(Arg))
+          if ((NNAtt && NNAtt->isNonNull(PVD->getFunctionScopeIndex())) ||
+              PVD->hasAttr<NonNullAttr>())
+            AI->addAttr(llvm::AttributeSet::get(getLLVMContext(),
+                                                AI->getArgNo() + 1,
+                                                llvm::Attribute::NonNull));
+
         if (Arg->getType().isRestrictQualified())
           AI->addAttr(llvm::AttributeSet::get(getLLVMContext(),
                                               AI->getArgNo() + 1,
                                               llvm::Attribute::NoAlias));
 
         // Ensure the argument is the correct type.
         if (V->getType() != ArgI.getCoerceToType())
           V = Builder.CreateBitCast(V, ArgI.getCoerceToType());

test/CodeGen/nonnull.c

+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm < %s | FileCheck %s
+
+// CHECK: define void @foo(i32* nonnull %x)
+void foo(int * __attribute__((nonnull)) x) {
+  *x = 0;
+}
+
+// CHECK: define void @bar(i32* nonnull %x)
+void bar(int * x) __attribute__((nonnull(1)))  {
+  *x = 0;
+}
+
+// CHECK: define void @bar2(i32* %x, i32* nonnull %y)
+void bar2(int * x, int * y) __attribute__((nonnull(2)))  {
+  *x = 0;
+}
+