[PATCH 3/5] libstdc++: Optimize simd conversions on x86-64

[Matthias Kretz]

Without SSSE3/SSE4, GCC falls back to converting scalars, which is not
efficient.

Signed-off-by: Matthias Kretz <m.kretz@gsi.de>

libstdc++-v3/ChangeLog:

	* include/bits/simd_vec.h (basic_vec::basic_vec): Improve
	code-gen of conversions from 4-Byte 2/3/4 register vec to
	single-register 1/2-Byte integer.
	* include/bits/vec_ops.h (__vec_interleave_lo)
	(__vec_interleave_hi): New.
	(__vec_cast): Improve code-gen of conversions without SSE4
	instructions.
	* testsuite/std/simd/sse2_efficient_cvt_x4.cc: New test.
---
 libstdc++-v3/include/bits/simd_vec.h          |  84 ++++++++++++++
 libstdc++-v3/include/bits/vec_ops.h           |  70 ++++++++++++
 .../std/simd/sse2_efficient_cvt_x4.cc         | 105 ++++++++++++++++++
 3 files changed, 259 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/std/simd/sse2_efficient_cvt_x4.cc


--
──────────────────────────────────────────────────────────────────────────
 Dr. Matthias Kretz                           https://mattkretz.github.io
 GSI Helmholtz Center for Heavy Ion Research               https://gsi.de
 std::simd
──────────────────────────────────────────────────────────────────────────
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