[PATCH] D114487: [LAA] Support runtime checks for select GEP base pointers.

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka added a comment.

This patch is causing false reports with msan. I am trying to creduce the code. It's with TensorFlow, so far it's quite complicated.

I see that before the patch the pass produced

  vector.memcheck:                                  ; preds = %vector.scevcheck
    %scevgep77 = getelementptr i32, i32* %retval.0.i.sroa.sel, i64 1, !dbg !1439
    %scevgep7778 = bitcast i32* %scevgep77 to i8*, !dbg !1439
    %bound0 = icmp ult i8* %scevgep73, %scevgep7778, !dbg !1439
    %bound1 = icmp ult i8* %retval.0.i.sroa.sel76, %scevgep7475, !dbg !1439
    %found.conflict = and i1 %bound0, %bound1, !dbg !1439
    br i1 %found.conflict, label %scalar.ph, label %vector.ph

After the patch it's more complicated:

  vector.memcheck:                                  ; preds = %vector.scevcheck
    %scevgep79 = getelementptr %"union.absl::container_internal::map_slot_type", %"union.absl::container_internal::map_slot_type"* %33, i64 0, i32 0, i32 1, i32 1, i32 0, i32 2, !dbg !1439
    %scevgep7980 = bitcast i32* %scevgep79 to i8*, !dbg !1439
    %scevgep81 = getelementptr %"union.absl::container_internal::map_slot_type", %"union.absl::container_internal::map_slot_type"* %33, i64 0, i32 0, i32 1, i32 2, i64 0, !dbg !1439
    %bound0 = icmp ult i8* %scevgep73, %scevgep78, !dbg !1439
    %bound1 = icmp ult i8* %scevgep7677, %scevgep7475, !dbg !1439
    %found.conflict = and i1 %bound0, %bound1, !dbg !1439
    %bound082 = icmp ult i8* %scevgep73, %scevgep81, !dbg !1439
    %bound183 = icmp ult i8* %scevgep7980, %scevgep7475, !dbg !1439
    %found.conflict84 = and i1 %bound082, %bound183, !dbg !1439
    %conflict.rdx = or i1 %found.conflict, %found.conflict84, !dbg !1439
    br i1 %conflict.rdx, label %scalar.ph, label %vector.ph

Then then when Msan instruments the code, it detects branch on uninitialized %conflict.rdx

I will continue to minimize the reproducer.
Should we revert the patch, because it breaks Msan and maybe there is a chance the bounds are calculated incorrectly?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114487/new/

https://reviews.llvm.org/D114487