[X86] Remove cvtps2ph xmm->xmm from store folding tables. Add the evex...

[X86] Remove cvtps2ph xmm->xmm from store folding tables. Add the evex versions of cvtps2ph to the store folding tables.

The memory form of the xmm->xmm version only writes 64-bits. If we use it in the folding tables and its get used for a stack spill, only half the slot will be written. Then a reload may read all 128-bits which will pull in garbage. But without the spill the upper bits of the register would have been zero. By not folding we would preserve the zeros.

llvm-svn: 321950