From: Reid Kleckner <rnk@google.com>
Date: Mon, 2 May 2016 22:42:34 +0000 (+0000)
Subject: Fix argument expansion of reference fields of structs
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=47e2e614ab54a6ec834d20d5a3582895b1568a7b;p=clang

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@268321 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 04c0a11600..50ea7f7cc3 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -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())) {
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 8329e52bde..3ecd8e3f0f 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -3667,6 +3667,10 @@ RValue CodeGenFunction::EmitRValueForField(LValue LV,
   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");
diff --git a/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp b/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
index a5cb98d41b..f7dc524067 100644
--- a/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
+++ b/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
@@ -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(); }