Vectors of bfloat are a storage format only; you're supposed to
explicitly convert them to a wider type to do arithmetic on them.
But currently, if you write something like
bfloat16x4_t test(bfloat16x4_t a, bfloat16x4_t b) { return a + b; }
then the clang frontend accepts it without error, and (ARM or AArch64)
isel fails to generate code for it.
Added a rule in Sema that forbids the attempt from even being made,
and tests that check it. In particular, we also outlaw arithmetic
between vectors of bfloat and any other vector type.
Patch by Luke Cheeseman.
Reviewed By: LukeGeeson
Differential Revision: https://reviews.llvm.org/D85009
Summary:
This patch upstreams support for a new storage only bfloat16 C type.
This type is used to implement primitive support for bfloat16 data, in
line with the Bfloat16 extension of the Armv8.6-a architecture, as
detailed here:
https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/arm-architecture-developments-armv8-6-a
The bfloat type, and its properties are specified in the Arm Architecture
Reference Manual:
https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile
In detail this patch:
- introduces an opaque, storage-only C-type __bf16, which introduces a new bfloat IR type.
This is part of a patch series, starting with command-line and Bfloat16
assembly support. The subsequent patches will upstream intrinsics
support for BFloat16, followed by Matrix Multiplication and the
remaining Virtualization features of the armv8.6-a architecture.
The following people contributed to this patch:
- Luke Cheeseman
- Momchil Velikov
- Alexandros Lamprineas
- Luke Geeson
- Simon Tatham
- Ties Stuij
Reviewers: SjoerdMeijer, rjmccall, rsmith, liutianle, RKSimon, craig.topper, jfb, LukeGeeson, fpetrogalli
Reviewed By: SjoerdMeijer
Subscribers: labrinea, majnemer, asmith, dexonsmith, kristof.beyls, arphaman, danielkiss, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D76077
Simon Tatham