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llvm-mirror/unittests/Target
Simon Tatham c48cf33847 [ARM,MVE] Revise immediate VBIC/VORR to look more like NEON.
Summary:
In NEON, the immediate forms of VBIC and VORR are each represented as
a single MC instruction, which takes its immediate operand already
encoded in a NEON-friendly format: 8 data bits, plus some control bits
indicating how to expand them into a full vector.

In MVE, we represented immediate VBIC and VORR as four separate MC
instructions each, for an 8-bit immediate shifted left by 0, 8, 16 or
24 bits. For each one, the value of the immediate operand is in the
'natural' form, i.e. the numerical value that would actually be BICed
or ORRed into each vector lane (and also the same value shown in
assembly). For example, MVE_VBICIZ16v4i32 takes an operand such as
0xab0000, which NEON would represent as 0xab | (control bits << 8).

The MVE approach is superficially nice (it makes assembly input and
output easy, and it's also nice if you're manually constructing
immediate VBICs). But it turns out that it's better for isel if we
make the NEON and MVE instructions work the same, because the
ARMISD::VBICIMM and VORRIMM node types already encode their immediate
into the NEON format, so it's easier if we can just use it.

Also, this commit reduces the total amount of code rather than
increasing it, which is surely an indication that it really is simpler
to do it this way!

Reviewers: dmgreen, ostannard, miyuki, MarkMurrayARM

Reviewed By: dmgreen

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73205
2020-01-23 11:53:52 +00:00
..
AArch64 CMake: Make most target symbols hidden by default 2020-01-14 19:46:52 -08:00
ARM [ARM,MVE] Revise immediate VBIC/VORR to look more like NEON. 2020-01-23 11:53:52 +00:00
PowerPC [NFC][PowerPC] Remove unnecessary link components. 2020-01-16 21:22:51 -05:00
WebAssembly CMake: Make most target symbols hidden by default 2020-01-14 19:46:52 -08:00
X86 [PGO][PGSO] Distinguish queries from unit tests and explicitly enable for the existing IR passes only. NFC. 2019-12-04 09:35:50 -08:00
CMakeLists.txt