From 13560bc4de68dca7c4ae5771b6ca5d0dd2018bbf Mon Sep 17 00:00:00 2001 From: lkcl Date: Sat, 9 Apr 2022 03:24:03 +0100 Subject: [PATCH] --- openpower/sv/svp64.mdwn | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/openpower/sv/svp64.mdwn b/openpower/sv/svp64.mdwn index 6d05c31da..bb89bb886 100644 --- a/openpower/sv/svp64.mdwn +++ b/openpower/sv/svp64.mdwn @@ -174,13 +174,20 @@ Following the prefix will be the suffix: this is simply a 32-bit v3.0B / v3.1 instruction. That instruction becomes "prefixed" with the SVP context: the Remapped Encoding field (RM). +It is important to note that unlike v3.1 64-bit prefixed instructions +there is insufficient space in `RM` to provide identification of +any SVP64 Fields without first partially decoding the +32-bit suffix. Extreme caution and care must therefore be taken +when extending SVP64 in future, to not create unnecessary relationships +between prefix and suffix that could complicate decoding, adding latency. + # Common RM fields The following fields are common to all Remapped Encodings: | Field Name | Field bits | Description | |------------|------------|----------------------------------------| -| MASKMODE | `0` | Execution (predication) Mask Kind | +| MASKMODE | `0` | Execution (predication) Mask Kind | | MASK | `1:3` | Execution Mask | | ELWIDTH | `4:5` | Element Width | | ELWIDTH_SRC | `6:7` | Element Width for Source | -- 2.30.2