[Patch] Fix for incorrect ABI in case we have an unused union argument passed by value

[Karthik Bhat]

Hi,
Please find the patch for incorrect ABI in case we have a union argument
passed by value.

Index: test/CodeGen/transparent-union.c
===================================================================
--- test/CodeGen/transparent-union.c (revision 188794)
+++ test/CodeGen/transparent-union.c (working copy)
@@ -1,9 +1,7 @@
 // RUN: %clang_cc1 -Werror -triple i386-unknown-unknown -emit-llvm -o %t %s
 // RUN: FileCheck < %t %s
-//
-// FIXME: Note that we don't currently get the ABI right here. f0() should
be
-// f0(i8*).

+
 typedef union {
   void *f0;
 } transp_t0 __attribute__((transparent_union));
@@ -11,7 +9,7 @@
 void f0(transp_t0 obj);

 // CHECK-LABEL: define void @f1_0(i32* %a0)
-// CHECK:  call void @f0(%union.transp_t0* byval align 4 %{{.*}})
+// CHECK:  call void @f0(i8* %{{.*}})
 // CHECK:  call void %{{.*}}(i8* %{{[a-z0-9]*}})
 // CHECK: }
 void f1_0(int *a0) {
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp (revision 188794)
+++ lib/CodeGen/TargetInfo.cpp (working copy)
@@ -325,10 +325,11 @@
   //
   // FIXME: This needs to be generalized to handle classes as well.
   const RecordDecl *RD = RT->getDecl();
-  if (!RD->isStruct() || isa<CXXRecordDecl>(RD))
+  if (!(RD->isStruct() || RD->isUnion()) || isa<CXXRecordDecl>(RD))
     return false;

   uint64_t Size = 0;
+  uint64_t CurrentElmtSize = 0;

   for (RecordDecl::field_iterator i = RD->field_begin(), e =
RD->field_end();
          i != e; ++i) {
@@ -343,7 +344,14 @@
     if (FD->isBitField())
       return false;

+    if (!RD->isUnion())
     Size += Context.getTypeSize(FD->getType());
+    else {
+      //Size of union is size of it's largest element.
+      CurrentElmtSize = Context.getTypeSize(FD->getType());
+      if (CurrentElmtSize > Size)
+        Size = CurrentElmtSize;
+    }
   }

   // Make sure there are not any holes in the struct.


Regards
Karthik Bhat
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