[PATCH] D26438: [Verifier] Add verification for TBAA metadata

[Manman Ren via llvm-commits]

manmanren added a comment.

In https://reviews.llvm.org/D26438#591404, @sanjoy wrote:

> In https://reviews.llvm.org/D26438#591399, @manmanren wrote:
>
> > > There is this bit of language in the TBAA implementation:
> > > 
> > >   // The second field is the access type node, it
> > >   // must be a scalar type node.
> > > 
> > > 
> > > but in the TBAA metadata generated by clang it seems like we have access types like `!{!"int", !N, i64 0}` which look like struct nodes.
> >
> > Can you give an example where clang generates a struct path tag node where the 2nd field is not a scalar type node?
>
>
> That seems to be the case everywhere.  E.g.
>
>   struct S {
>        int i;
>        float f;
>   };
>  
>   float f(struct S* s) {
>        return s->f;
>   }
>
>
> compiles to
>
>   ; ModuleID = 'x.c'
>   source_filename = "x.c"
>   target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
>   target triple = "x86_64-apple-macosx10.12.0"
>  
>   %struct.S = type { i32, float }
>  
>   ; Function Attrs: norecurse nounwind readonly ssp uwtable
>   define float @f(%struct.S* nocapture readonly %s) local_unnamed_addr #0 {
>   entry:
>     %f = getelementptr inbounds %struct.S, %struct.S* %s, i64 0, i32 1
>     %0 = load float, float* %f, align 4, !tbaa !2
>     ret float %0
>   }
>  
>   attributes #0 = { ... }
>  
>   !llvm.module.flags = !{!0}
>   !llvm.ident = !{!1}
>  
>   !0 = !{i32 1, !"PIC Level", i32 2}
>   !1 = !{!"clang version 4.0.0 (http://llvm.org/git/clang.git b74377b0a34a33cb3c7b565f0e543cd3e56b3f6b) (llvm/trunk 286280)"}
>   !2 = !{!3, !7, i64 4}
>   !3 = !{!"S", !4, i64 0, !7, i64 4}
>   !4 = !{!"int", !5, i64 0}
>   !5 = !{!"omnipotent char", !6, i64 0}
>   !6 = !{!"Simple C/C++ TBAA"}
>   !7 = !{!"float", !5, i64 0}
>
>
> The tag for the load instruction is `!2` whose access type is `!7` == `!{!"float", !5, i64 0}`.


!7 is a scalar type node, it is a float, right?

Manman


https://reviews.llvm.org/D26438