[PATCH] D126270: [InstCombine] Preserve !nosanitize for newly created instructions.

[Mingjie Xu via Phabricator via llvm-commits]

Enna1 added a comment.

I came up a workaround, but it may not elegant enough i think.
In AddressSanitizer.cpp `isInterestingPointerComparison()`, we add a check if the two following conditions satisfied:

- the ICmpInst is used as a branchinst predicate
- the branchinst has a successor containing callback inserted by UBSan(e.g. __ubsan_handle_pointer_overflow)

If so, ASan will not take this ICmpInst as an interesting pointer compairson, as will not have a false positive on this.

  define dso_local i32 @main() local_unnamed_addr #0 !dbg !9 {
    %1 = alloca [10 x i8], align 1
    call void @llvm.dbg.declare(metadata [10 x i8]* %1, metadata !14, metadata !DIExpression()), !dbg !19
    %2 = ptrtoint [10 x i8]* %1 to i64, !dbg !20, !nosanitize !13
    %.not = icmp ugt [10 x i8]* %1, inttoptr (i64 -5 to [10 x i8]*), !dbg !20
    br i1 %.not, label %3, label %5, !dbg !20, !prof !21, !nosanitize !13
  
  3:                                                ; preds = %0
    %4 = add i64 %2, 4, !dbg !20, !nosanitize !13
    call void @__ubsan_handle_pointer_overflow(i8* bitcast ({ { [7 x i8]*, i32, i32 } }* @0 to i8*), i64 %2, i64 %4) #3, !dbg !20, !nosanitize !13
    br label %5, !dbg !20, !nosanitize !13


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D126270/new/

https://reviews.llvm.org/D126270