[PATCH] D83394: [AMDGPU] Avoid splitting FLAT offsets in unsafe ways

Thu Oct 1 04:23:57 PDT 2020

foad added a comment.

In D83394#2305735 <https://reviews.llvm.org/D83394#2305735>, @JonChesterfield wrote:

> I'm seeing (difficult to minimise) failure modes with gfx10 that look the same as those on gfx9 before this patch. I also see the comment:
>
>> "gfx10 does have a bug with flat offsets"
>
> Is there a corresponding patch needed for gfx10?

This patch affected gfx10 just as much as gfx9, so there is no extra patch required for gfx10.

I am confused about the gfx10 bug. I assume it refers to this:

  def FeatureFlatSegmentOffsetBug : SubtargetFeature<"flat-segment-offset-bug",
    "HasFlatSegmentOffsetBug",
    "true",
    "GFX10 bug, inst_offset ignored in flat segment"
  >;

But (a) I think this is just the intended behaviour of the hardware, so I wouldn't call it a bug, and (b) I think gfx9 works the same way, otherwise there would have been no need for this patch in the first place!

Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D83394