[PATCH] D57504: RFC: Prototype & Roadmap for vector predication in LLVM

[Luke Kenneth Casson Leighton via Phabricator via llvm-commits]

lkcl added a comment.

In D57504#1872392 <https://reviews.llvm.org/D57504#1872392>, @craig.topper wrote:

> MMX does use the X87 FP register file, but they can't coexist at the same. The first use of MMX marks the X87 register stack as occupied. I can't remember if it alters the data or not. An explicit emms instruction has to be done at the end of the MMX code to erase the MMX data and make the registers usable for X87 again.


craig, thank you for correcting me. that makes a lot of sense as i can just imagine the x87 designers going "argh, how are we going to avoid a pipeline clash / mess, here" :)

you get the principle i am sure, even though MMX is not a suitable example.


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