[PATCH] D21594: [esan|cfrag] Add counters for struct array accesses

[Qin Zhao via llvm-commits]

zhaoqin added a comment.

In http://reviews.llvm.org/D21594#472524, @dberlin wrote:

> You are right. What will happen is it will not look like a structure field
>  access, and will use i8 or something so it can do the calculation.
>  I'll paste a clang generated example in a bit


I just tried a manual test example as below:

%struct.RT = type { i8, [10 x [20 x i32]], i8 }
%struct.ST = type { i32, double, %struct.RT }

define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
entry:

  %arrayidx = getelementptr inbounds %struct.ST, %struct.ST* %s, i64 0, i32 -1
  ret i32* %arrayidx

}

which I tried gep on struct.ST with a negative field.
And I get the error that invalid getelementptr indices:

$ /usr/local/google/home/zhaoqin/Workspace/LLVM/builds/build_x64_rel.git/./bin/opt < /usr/local/google/home/zhaoqin/Workspace/LLVM/llvm.git/test/Instrumentation/EfficiencySanitizer/struct_field_gep.ll -esan -esan-cache-frag -S
/usr/local/google/home/zhaoqin/Workspace/LLVM/builds/build_x64_rel.git/./bin/opt: <stdin>:28:50: error: invalid getelementptr indices

  %arrayidx = getelementptr inbounds %struct.ST, %struct.ST* %s, i64 0, i32 -1
                                                                                 ^


http://reviews.llvm.org/D21594