Combination of O3 and UBSan makes seadsa crash on input analysis about sea-dsa HOT 2 OPEN

It seems that the check in DsaLocal at line 667 is specifically made for one or several gep instructions starting from NULL.

Here the crash is acually a load of a pointer, which is obtained from a load on a GEP null, so two levels of indirection:

  %arrayidx87.us = getelementptr inbounds i8*, i8** null, i64 %indvars.iv99
  %arrayidx.us = bitcast i8** %arrayidx87.us to float**
  %4 = load float*, float** %arrayidx.us, align 8, !tbaa !4
  %6 = bitcast float* %4 to i32*
  %7 = load i32, i32* %6, align 4, !tbaa !8

It is undefined behavior, but it is present due to UBSan.
I can submit a PR to fix this, but not sure what I should check, instead of simply transforming assert(!base.isNull()); into if(base.isNull()) return; in:

Probably the fix should avoid creating the null cell in the first place.

from sea-dsa.

Ok if I enable assertions with PR #131 it actually crashes on

after printing as a warning: Unexpected expression at valueCell: %4 = load float*, float** %arrayidx.us, align 8, !tbaa !4 .
This while in visitBitCastInst visiting %6 = bitcast float* %4 to i32* with %4 = load float*, float** %arrayidx.us, align 8, !tbaa !4

from sea-dsa.