[PATCH] D20789: Consecutive memory access in Loop Vectorizer - fixed and simplified

[Demikhovsky, Elena via llvm-commits]

Right. As you see, the distance between %op and %src is not checked.
%bound0 is some arithmetic between %op and %len
And
 %bound1 is some arithmetic between %src and %len

The loop just for the reference:
  while (len > 0) {
      *(reinterpret_cast<long long*>(op)) = *(reinterpret_cast<const long long*>(src));
        src += 8;
        op += 8;
        len -= 8;
  }

-  Elena

   >
   >mkuper added a comment.
   >
   >I tried building with r274114 (before this was reverted), and we did
   >generate a runtime alias check:
   >
   >  vector.memcheck:                                  ; preds = %min.iters.checked
   >    %7 = sub i32 -1, %len
   >    %8 = icmp sgt i32 %7, -9
   >    %smax9 = select i1 %8, i32 %7, i32 -9
   >    %9 = add i32 %len, %smax9
   >    %10 = add i32 %9, 8
   >    %11 = lshr i32 %10, 3
   >    %12 = zext i32 %11 to i64
   >    %13 = shl i64 %12, 3
   >    %scevgep = getelementptr i8, i8* %op, i64 %13
   >    %scevgep10 = getelementptr i8, i8* %src, i64 %13
   >    %bound0 = icmp ule i8* %op, %scevgep10
   >    %bound1 = icmp ule i8* %src, %scevgep
   >    %found.conflict = and i1 %bound0, %bound1
   >    %memcheck.conflict = and i1 %found.conflict, true
   >    %cast.crd = trunc i64 %n.vec to i32
   >    %14 = shl i32 %cast.crd, 3
   >    %ind.end = sub i32 %len, %14
   >    %15 = shl i64 %n.vec, 3
   >    %ind.end12 = getelementptr i8, i8* %op, i64 %15
   >    %ind.end14 = getelementptr i8, i8* %src, i64 %15
   >    br i1 %memcheck.conflict, label %scalar.ph, label %vector.ph
   >
   >I'm not sure this runtime check is correct, though.
   >
   >
   >Repository:
   >  rL LLVM
   >
   >https://reviews.llvm.org/D20789
   >
   >

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