[PATCH] [Polly][RTC] Use the domain to split alias groups.

[Johannes Doerfert]

================
Comment at: test/ScopInfo/aliasing_conditional_alias_groups_2.ll:6
@@ +5,3 @@
+;
+; CHECK: Alias Groups (2):
+;
----------------
grosser wrote:
> Before this change we got:
> 
>   %tmp38 = icmp ne i32 %b, 0
>   %tmp39 = select i1 %tmp38, i64 6, i64 1024
>   %polly.access.B = getelementptr i32* %B, i64 %tmp39
>   %tmp40 = select i1 %tmp38, i64 0, i64 7
>   %polly.access.A = getelementptr i32* %A, i64 %tmp40
>   %tmp41 = icmp ule i32* %polly.access.B, %polly.access.A
>   %tmp42 = select i1 %tmp38, i64 1024, i64 8
>   %polly.access.A1 = getelementptr i32* %A, i64 %tmp42
>   %tmp43 = select i1 %tmp38, i64 5, i64 0
>   %polly.access.B2 = getelementptr i32* %B, i64 %tmp43
>   %tmp44 = icmp ule i32* %polly.access.A1, %polly.access.B2
>   %tmp45 = or i1 %tmp41, %tmp44
> 
> 12 instructions
> 
> after this change we got:
> 
>   %polly.access.A = getelementptr i32* %A, i64 8
>   %tmp42 = icmp ule i32* %polly.access.A, %B
>   %polly.access.B1 = getelementptr i32* %B, i64 1024
>   %polly.access.A2 = getelementptr i32* %A, i64 7
>   %tmp43 = icmp ule i32* %polly.access.B1, %polly.access.A2
>   %tmp44 = or i1 %tmp42, %tmp43
>   %polly.access.A3 = getelementptr i32* %A, i64 1024
>   %polly.access.B4 = getelementptr i32* %B, i64 5
>   %tmp45 = icmp ule i32* %polly.access.A3, %polly.access.B4
>   %polly.access.B5 = getelementptr i32* %B, i64 6
>   %tmp46 = icmp ule i32* %polly.access.B5, %A
>   %tmp47 = or i1 %tmp45, %tmp46
>   %tmp48 = and i1 %tmp44, %tmp47
> 
> 13 instructions
> 
> This does not seem to be a clear improvement (in this case rather a small regression at least in terms of instruction count).
But it's more precise ;)

Just look at the alias groups we generate, two small precise ones instead of one overaproximated one :)

http://reviews.llvm.org/D5436