[Issue 17484] high penalty for vbroadcastsd with -mcpu=avx

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17484

--- Comment #1 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/dlang/dmd

https://github.com/dlang/dmd/commit/1f11aa0eb8f6087b7dbadeb770e4526ec9808ccc
fix Issue 17484 - high penalty for AVX-256 instructions with AVX-128 regs

- as the upper 128-bits are no longer zero, the CPU will save/restore
  them when that register is used with legacy SSE instructions
- avoid using vbroadcastsd which is a AVX-256 only instruction to
  initialize 128-bit XMM vectors

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