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diff --git a/openpower/sv/svp64_quirks.mdwn b/openpower/sv/svp64_quirks.mdwn
index b6662c901f53ecfee12733e3a4f62b0eae4068e1..3872e635bda48cabf1a5c52f14a67acf9648f7d6 100644 (file)
--- a/openpower/sv/svp64_quirks.mdwn
+++ b/openpower/sv/svp64_quirks.mdwn
@@ -487,3 +487,17 @@ FP32 result into the full 32 bits.
 Where this breaks down is when attempting to do half-width on
 BF16 or FP16 operations: there does not exist a BF8 or an IEE754 FP8
 format, so these should be avoided.
+
+# Vertical-First and Subvectors
+
+Documented in the [[sv/setvl]] page, Vertical-First goes through
+elements second instructions first and requires an explicit
+[[sv/svstep]] instruction to move to the next element,
+(whereas Horizontal-First
+loops through elements in full first before moving on to
+the next instruction): *Subvectors are considered "elements"*
+in Vertical-First Mode.
+
+This is conceptually quite easy to keep in mind that a Vertical-First
+instruction does one element at a time, and when SUBVL is set,
+that "element" in essence becomes a vec2/3/4.