Puny 24-byte structs are returned by value on SPARC.

Pad these structs up so they are sret-returned even on that
architecture.

llvm-svn: 199188

clang/test/CodeGen/sret.c

@@ -4,6 +4,8 @@ struct abc {
  long a;
  long b;
  long c;
+ long d;
+ long e;
 };
  
 struct abc foo1(void);

clang/test/CodeGen/sret2.c

@@ -4,6 +4,8 @@ struct abc {
  long a;
  long b;
  long c;
+ long d;
+ long e;
 };
  
 struct abc foo2(){}