On 5/1/2013 7:41 AM, Paul Gilmartin wrote:
Ah! We need UPTG. And the corresponding search function. And we need it to be serialized against concurrent updates (is it?)
UPT is a modal instruction. Thus, no "grande" form is needed. In 24- and 31-bit mode, nodes are eight bytes in length and codewords are four bytes long. In 64-bit mode, the sizes are automatically doubled: nodes are sixteen bytes in length and codewords are eight bytes long.
Although the entire update tree operation is encapsulated within a single millicode instruction, nothing in PoOp states that the updates appear atomic, as viewed from other CPUs, or that the tree is somehow serialized against updates from those CPUs. None of that is necessary for its intended purpose.
The very first paragraph in PoOp describing the UPT instruction explicitly states that it is "for use in sort/merge algorithms."
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