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The documentation for vzeroall appears inconsistent. The prose says:
The instruction zeros contents of all XMM or YMM registers.
The pseudocode below that, however, indicates that in 64-bit mode only registers ymm0 through ymm15 are affected:
IF (64-bit mode)
limit ←15
ELSE
limit ← 7
FOR i in 0 .. limit:
simd_reg_file[i][MAXVL-1:0] ← 0
On AVX-512 supporting machines clearing up to ymm15 is not the same as clearing "all" because ymm16 through ymm31 exist.
Is the prose or pseudocode correct?
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AVX uses sixteen YMM registers to perform a single instruction on multiple pieces of data (see SIMD). Each YMM register can hold and do simultaneous operations (math) on: eight 32-bit single-precision floating point numbers or. four 64-bit double-precision floating point numbers.
The AVX-512 instruction set increases the size of a CPU's register to enhance its performance. This boost in performance enables CPUs to crunch numbers faster, allowing users to run video/audio compression algorithms at faster speeds.
It seems like it was a description issue, if you will look at the latest SDM you will see that description was changed lately and now it says that VZEROALL does not changing YMM16...YMM31.
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