From: lkcl <lkcl@web>
Date: Wed, 4 Aug 2021 01:21:43 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: DRAFT_SVP64_0_1~512
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=90d3ed291a7d83f2cf1363ee2abf582743e5b609;p=libreriscv.git

---

diff --git a/openpower/sv/setvl.mdwn b/openpower/sv/setvl.mdwn
index b4024b4ac..11b3cbd46 100644
--- a/openpower/sv/setvl.mdwn
+++ b/openpower/sv/setvl.mdwn
@@ -111,6 +111,26 @@ the same instruction.  That would require two instructions.
 
 # setmvlhi
 
+In Vertical-First Mode the minimum expectation is that one scalar
+element may be executed by each instruction. There are however
+circumstances where it may be possible to execute more than one:
+determining a "safe minimum amount" may not be practical.
+
+Therefore, setmvlhi may specify, as determined by the compiler,
+exactly what that quantity is.  Unlike VL, which is an amount
+that, when requested, **must** be executed, VFhint may be set
+to an amount that the hardware is capable of.
+
+Critical to note are two things:
+
+1. VFhint must not be set by hardware to an amount that
+exceeds either MVL or the requested amount, and must set
+VFhint to at least 1 element.
+2. svstep will increment srcstep and dststep by VFhint,
+therefore when hardware says it can perform N element
+operations, hardware **MUST** perform N operations
+for every single instruction. 
+
 Form: SVL-Form (see [[isatables/fields.text]])
 
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