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LLVM Clang Switches MMX Intrinsics To Use SSE2 Instead
Following LLVM/Clang recently dropping support for AMD 3DNow! instructions, the open-source compiler stack is now pushing the MMX SIMD instruction set to a backseat
The pull request by James Knight explains:"The MMX instruction set is legacy, and the SSE2 variants are in every way superior, when they are available -- and they have been available since the Pentium 4 was released, 20 years ago. Targeting these older CPUs remains supported -- simply without the ability to use MMX compiler intrinsics. Worse, even if the user did write code that correctly calls _mm_empty() in the right places, LLVM may sometimes reorder x87 and mmx operations around each-other, unaware of this mode switching issue."
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