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Stop the instruction set war
Author: Agner Fog Date: 2010-01-10 01:41
Norman Yarvin wrote:
The x87 instruction set won't truly be obsolete until SSEx has support for floating-point formats of >64 bits.
I agree. We need XMM instructions with 80 bits, or better 128 bits, extended floating point precision before we can eliminate x87 completely. This feature should be optional because it is expensive to implement and few users would need it. There are also a few MMX conversion instructions that we need to implement as XMM instructions before we can eliminate the MMX registers.

But Microsoft has never supported the 80 bits (long double) precision in their compiler. And the first preliminary specification for x64 Windows banned x87 and MMX. For some reason, they changed their mind and allowed x87/MMX (See my manual on calling conventions).

All this just shows that we need coordination and planning rather than each company making its own decisions.

 
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