Andrea Di Biagio 77f62652c1 Reapply r249121 : "[FastISel][x86] Teach how to select SSE2/AVX bitcasts between 128/256-bit vector types." ...

This patch teaches FastIsel the following two things:
1) On SSE2, no instructions are needed for bitcasts between 128-bit vector types;
2) On AVX, no instructions are needed for bitcasts between 256-bit vector types.

Example:

  %1 = bitcast <4 x i31> %V to <2 x i64>

Before (-fast-isel -fast-isel-abort=1):

  FastIsel miss: %1 = bitcast <4 x i31> %V to <2 x i64>

Now we don't fall back to SelectionDAG and we correctly fold that computation
propagating the register associated to %V.

Originally reviewed here: http://reviews.llvm.org/D13347

llvm-svn: 249147

2015-10-02 16:08:05 +00:00

5.9 KiB

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