[Bug target/19530] MMX load intrinsic produces SSE superfluous instructions (movlps)

["guardia at sympatico dot ca" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From guardia at sympatico dot ca  2005-06-21 13:26 -------
Hum, it will be interesting to test this (it will have to wait a couple of
weeks), but the problem with this here is that there is no "mov" instructions
that can move stuff between MMX registers and SSE registers (MOVQ can't do it).
In SSE2, there is one (MOVQ), but not in the original SSE. So the compiler
generates movlps instructions from/to memory from/to SSE registers along MMX
calculations, and, in the original SSE case, ends up not being able to reduce
anymore than MMx->memory->XMMx->memory->MMx again for data that should have
stayed in MMX registers all along... it does not realize up front how expensive
it is to use XMM registers on "SSE1" along with MMX instructions.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19530