From d735b5e5bbf746e3e28123c79360f087dac037b7 Mon Sep 17 00:00:00 2001 From: lkcl Date: Sat, 3 Sep 2022 13:10:23 +0100 Subject: [PATCH] --- openpower/sv/remap.mdwn | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/openpower/sv/remap.mdwn b/openpower/sv/remap.mdwn index 2a93e5f80..59f00316d 100644 --- a/openpower/sv/remap.mdwn +++ b/openpower/sv/remap.mdwn @@ -667,6 +667,20 @@ makes it easier. Dimensions are calculated exactly as `svindex`. `rmm` and `mm` are as per `svindex`. +*Programmer's Note: offsets for `svshape2` may be specified in the range +0-7. Given that the principle of Simple-V is to fit on top of +byte-addressable register files and that GPR and FPR are 64-bit (8 bytes) +it should be clear that the offset may, when `elwidth=8`, begin an +element-level operation starting element zero at any arbitrary byte. +On cursory examination attempting to go **beyond** the range 0-7 seems +inadequate until it is recalled that the **next GPR or FPR** is an +alias for an offset in the range 8-15. Thus by simply increasing +the starting Vector point of the operation to the next register it +can be seen that the offset of 0-7 would be sufficient. Unfortunately +however some operations are EXTRA2-encoded which does in fact leave +them inaccessible. TODO: decide if the decision to sacrifice one +bit of `offs` in favour of an `inv` bit is worth it. +* # TODO -- 2.30.2