r268321 - Fix argument expansion of reference fields of structs

[Reid Kleckner via cfe-commits]

Author: rnk
Date: Mon May  2 17:42:34 2016
New Revision: 268321

URL: http://llvm.org/viewvc/llvm-project?rev=268321&view=rev
Log:
Fix argument expansion of reference fields of structs

r268261 made Clang "expand" more struct arguments on Windows. It removed
the check for 'RD->isCLike()', which was preventing us from attempting
to expand structs with reference type fields.

Our expansion code was attempting to load and pass each field of the
type in turn. We were accidentally doing one to many loads on reference
type fields.

On the function prologue side, we can use
EmitLValueForFieldInitialization, which obviously gets the address of
the field. On the call side, I tweaked EmitRValueForField directly,
since this is the only use of this method.

Fixes PR27607

Modified:
    cfe/trunk/lib/CodeGen/CGCall.cpp
    cfe/trunk/lib/CodeGen/CGExpr.cpp
    cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp

Modified: cfe/trunk/lib/CodeGen/CGCall.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCall.cpp?rev=268321&r1=268320&r2=268321&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGCall.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGCall.cpp Mon May  2 17:42:34 2016
@@ -948,7 +948,7 @@ void CodeGenFunction::ExpandTypeFromArgs
     }
     for (auto FD : RExp->Fields) {
       // FIXME: What are the right qualifiers here?
-      LValue SubLV = EmitLValueForField(LV, FD);
+      LValue SubLV = EmitLValueForFieldInitialization(LV, FD);
       ExpandTypeFromArgs(FD->getType(), SubLV, AI);
     }
   } else if (isa<ComplexExpansion>(Exp.get())) {

Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=268321&r1=268320&r2=268321&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExpr.cpp Mon May  2 17:42:34 2016
@@ -3667,6 +3667,10 @@ RValue CodeGenFunction::EmitRValueForFie
   case TEK_Aggregate:
     return FieldLV.asAggregateRValue();
   case TEK_Scalar:
+    // This routine is used to load fields one-by-one to perform a copy, so
+    // don't load reference fields.
+    if (FD->getType()->isReferenceType())
+      return RValue::get(FieldLV.getPointer());
     return EmitLoadOfLValue(FieldLV, Loc);
   }
   llvm_unreachable("bad evaluation kind");

Modified: cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp?rev=268321&r1=268320&r2=268321&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp Mon May  2 17:42:34 2016
@@ -217,6 +217,28 @@ void big_arg(Big s) {}
 // WIN32: define void @"\01?big_arg@@YAXUBig@@@Z"(%struct.Big* byval align 4 %s)
 // WIN64: define void @"\01?big_arg@@YAXUBig@@@Z"(%struct.Big* %s)
 
+// PR27607: We would attempt to load i32 value out of the reference instead of
+// just loading the pointer from the struct during argument expansion.
+struct RefField {
+  RefField(int &x);
+  int &x;
+};
+void takes_ref_field(RefField s) {}
+// LINUX-LABEL: define void @_Z15takes_ref_field8RefField(%struct.RefField* byval align 4 %s)
+// WIN32: define void @"\01?takes_ref_field@@YAXURefField@@@Z"(i32* %s.0)
+// WIN64: define void @"\01?takes_ref_field@@YAXURefField@@@Z"(i64 %s.coerce)
+
+void pass_ref_field() {
+  int x;
+  takes_ref_field(RefField(x));
+}
+// LINUX-LABEL: define void @_Z14pass_ref_fieldv()
+// LINUX: call void @_Z15takes_ref_field8RefField(%struct.RefField* byval align 4 %{{.*}})
+// WIN32-LABEL: define void @"\01?pass_ref_field@@YAXXZ"()
+// WIN32: call void @"\01?takes_ref_field@@YAXURefField@@@Z"(i32* %{{.*}})
+// WIN64-LABEL: define void @"\01?pass_ref_field@@YAXXZ"()
+// WIN64: call void @"\01?takes_ref_field@@YAXURefField@@@Z"(i64 %{{.*}})
+
 class Class {
  public:
   Small thiscall_method_small() { return Small(); }