From: lkcl Date: Mon, 21 Dec 2020 03:54:10 +0000 (+0000) Subject: (no commit message) X-Git-Tag: convert-csv-opcode-to-binary~1107 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=03220ab26c3fca7c62e8a0afc6d6221c8005000e;p=libreriscv.git --- diff --git a/openpower/sv/svp_rewrite/svp64.mdwn b/openpower/sv/svp_rewrite/svp64.mdwn index 8c3a2061f..37a6dd74f 100644 --- a/openpower/sv/svp_rewrite/svp64.mdwn +++ b/openpower/sv/svp_rewrite/svp64.mdwn @@ -206,7 +206,7 @@ These are the modes: * **ffirst** or data-dependent fail-on-first: see separate section. the vector may be truncated depending on certain criteria. * **sat mode** or saturation: clamps each elemrnt result to a min/max rather than overflows / wraps. allows signed and unsigned clamping. * **reduce mode**. a mapreduce is performed. the result is a scalar. a result vector however is required, as the upper elements may be used to store intermediary computations. the result of the mapreduce is in the first element with a nonzero predicate bit. see separate section below. - note that reduce mode only applies to 2 src operations. + note that there are comprehensive caveats when using this mode. * **pred-result** will test the result (CR testing selects a bit of CR and inverts it, just like branch testing) and if the test fails it is as if the predicate bit was zero. When Rc=1 the CR element (CR0) however is still stored in the CR regfile. This scheme does not apply to crops (crand, cror). Note that ffirst and reduce modes are not anticipated to be high-performance in some implementations. ffirst due to interactions with VL, and reduce due to it requiring additional operations to produce a result. normal, saturate and pred-result are however independent and may easily be parallelised to give high performance, regardless of the value of VL.