[CodeGen] Don't reemit expressions for pass_object_size params.

This fixes an assertion failure in cases where we had expression
statements that declared variables nested inside of pass_object_size
args. Since we were emitting the same ExprStmt twice (once for the arg,
once for the @llvm.objectsize call), we were getting issues with
redefining locals.

This also means that we can be more lax about when we emit
@llvm.objectsize for pass_object_size args: since we're reusing the
arg's value itself, we don't have to care so much about side-effects.

llvm-svn: 295935

1 files changed, 13 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 446f2a039f8..19b9c9b1d59 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -420,10 +420,11 @@ getDefaultBuiltinObjectSizeResult(unsigned Type, llvm::IntegerType *ResType) {
 
 llvm::Value *
 CodeGenFunction::evaluateOrEmitBuiltinObjectSize(const Expr *E, unsigned Type,
-                                                 llvm::IntegerType *ResType) {
+                                                 llvm::IntegerType *ResType,
+                                                 llvm::Value *EmittedE) {
   uint64_t ObjectSize;
   if (!E->tryEvaluateObjectSize(ObjectSize, getContext(), Type))
-    return emitBuiltinObjectSize(E, Type, ResType);
+    return emitBuiltinObjectSize(E, Type, ResType, EmittedE);
   return ConstantInt::get(ResType, ObjectSize, /*isSigned=*/true);
 }
 
@@ -432,9 +433,14 @@ CodeGenFunction::evaluateOrEmitBuiltinObjectSize(const Expr *E, unsigned Type,
 ///   - A llvm::Argument (if E is a param with the pass_object_size attribute on
 ///     it)
 ///   - A call to the @llvm.objectsize intrinsic
+///
+/// EmittedE is the result of emitting `E` as a scalar expr. If it's non-null
+/// and we wouldn't otherwise try to reference a pass_object_size parameter,
+/// we'll call @llvm.objectsize on EmittedE, rather than emitting E.
 llvm::Value *
 CodeGenFunction::emitBuiltinObjectSize(const Expr *E, unsigned Type,
-                                       llvm::IntegerType *ResType) {
+                                       llvm::IntegerType *ResType,
+                                       llvm::Value *EmittedE) {
   // We need to reference an argument if the pointer is a parameter with the
   // pass_object_size attribute.
   if (auto *D = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts())) {
@@ -457,10 +463,10 @@ CodeGenFunction::emitBuiltinObjectSize(const Expr *E, unsigned Type,
   // LLVM can't handle Type=3 appropriately, and __builtin_object_size shouldn't
   // evaluate E for side-effects. In either case, we shouldn't lower to
   // @llvm.objectsize.
-  if (Type == 3 || E->HasSideEffects(getContext()))
+  if (Type == 3 || (!EmittedE && E->HasSideEffects(getContext())))
     return getDefaultBuiltinObjectSizeResult(Type, ResType);
 
-  Value *Ptr = EmitScalarExpr(E);
+  Value *Ptr = EmittedE ? EmittedE : EmitScalarExpr(E);
   assert(Ptr->getType()->isPointerTy() &&
          "Non-pointer passed to __builtin_object_size?");
 
@@ -965,7 +971,8 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
 
     // We pass this builtin onto the optimizer so that it can figure out the
     // object size in more complex cases.
-    return RValue::get(emitBuiltinObjectSize(E->getArg(0), Type, ResType));
+    return RValue::get(emitBuiltinObjectSize(E->getArg(0), Type, ResType,
+                                             /*EmittedE=*/nullptr));
   }
   case Builtin::BI__builtin_prefetch: {
     Value *Locality, *RW, *Address = EmitScalarExpr(E->getArg(0));