[NFC] compatibility: add test for allocsize attribute

[reames]

Landed as aade28ea, I forgot to include the review link.

llvm/test/Bitcode/compatibility.ll

exit:
   ; CHECK: phi i32 [ %v1, %L1 ], [ %v2, %L2 ], [ %op1, %entry ]
 
   select i1 true, i32 0, i32 1
   ; CHECK: select i1 true, i32 0, i32 1
   select <2 x i1> <i1 true, i1 false>, <2 x i8> <i8 2, i8 3>, <2 x i8> <i8 3, i8 2>
   ; CHECK: select <2 x i1> <i1 true, i1 false>, <2 x i8> <i8 2, i8 3>, <2 x i8> <i8 3, i8 2>
 
   call void @f.nobuiltin() builtin
-  ; CHECK: call void @f.nobuiltin() #46
+  ; CHECK: call void @f.nobuiltin() #48
 
   call fastcc noalias i32* @f.noalias() noinline
   ; CHECK: call fastcc noalias i32* @f.noalias() #12
   tail call ghccc nonnull i32* @f.nonnull() minsize
   ; CHECK: tail call ghccc nonnull i32* @f.nonnull() #7
 
   freeze i32 %op1
   ; CHECK: freeze i32 %op1

 %named_type = type [8 x i8]
 declare void @byval_type(i32* byval(i32) align 2)
 declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
 declare void @byval_named_type(%named_type* byval(%named_type))
 ; CHECK: declare void @byval_type(i32* byval(i32) align 2)
 ; CHECK: declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
 ; CHECK: declare void @byval_named_type([8 x i8]* byval([8 x i8]))
 
+declare void @f.allocsize_one(i32) allocsize(0)
+declare void @f.allocsize_two(i32, i32) allocsize(1, 0)
+; CHECK: Function Attrs: allocsize(0)
+; CHECK: declare void @f.allocsize_one(i32)
+; CHECK: Function Attrs: allocsize(1,0)
+; CHECK: declare void @f.allocsize_two(i32, i32)
+
 ; CHECK: attributes #0 = { alignstack=4 }
 ; CHECK: attributes #1 = { alignstack=8 }
 ; CHECK: attributes #2 = { alwaysinline }
 ; CHECK: attributes #3 = { cold }
 ; CHECK: attributes #4 = { convergent }
 ; CHECK: attributes #5 = { inlinehint }
 ; CHECK: attributes #6 = { jumptable }
 ; CHECK: attributes #7 = { minsize }

 ; CHECK: attributes #38 = { argmemonly nounwind }
 ; CHECK: attributes #39 = { nounwind readonly }
 ; CHECK: attributes #40 = { inaccessiblemem_or_argmemonly nofree nosync nounwind willreturn }
 ; CHECK: attributes #41 = { writeonly }
 ; CHECK: attributes #42 = { speculatable }
 ; CHECK: attributes #43 = { strictfp }
 ; CHECK: attributes #44 = { nosanitize_coverage }
 ; CHECK: attributes #45 = { disable_sanitizer_instrumentation }
-; CHECK: attributes #46 = { builtin }
+; CHECK: attributes #46 = { allocsize(0) }
+; CHECK: attributes #47 = { allocsize(1,0) }
+; CHECK: attributes #48 = { builtin }
 
 ;; Metadata
 
 ; Metadata -- Module flags
 !llvm.module.flags = !{!0, !1, !2, !4, !5, !6}
 ; CHECK: !llvm.module.flags = !{!0, !1, !2, !4, !5, !6}
 
 !0 = !{i32 1, !"mod1", i32 0}