From d2999932625d2cab25bb2081f7da915411e65ad3 Mon Sep 17 00:00:00 2001 From: Andrew Waterman Date: Tue, 6 Aug 2024 01:24:33 -0700 Subject: [PATCH] Add note that presence of pack[w] implies presence of zext.h (#1580) --- src/b-st-ext.adoc | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/src/b-st-ext.adoc b/src/b-st-ext.adoc index fa26a7866..9b73fbc19 100644 --- a/src/b-st-ext.adoc +++ b/src/b-st-ext.adoc @@ -2386,6 +2386,13 @@ Included in:: |Ratified |=== +NOTE: For RV32, the `pack` instruction with _rs2_=`x0` is the `zext.h` +instruction. +Hence, for RV32, any extension that contains the `pack` instruction also +contains the `zext.h` instruction (but not necessarily the `c.zext.h` +instruction, which is only guaranteed to exist if both the Zcb and Zbb +extensions are implemented). + <<< [#insns-packh,reftext="Pack low bytes of registers"] ==== packh @@ -2484,6 +2491,13 @@ Included in:: |Ratified |=== +NOTE: For RV64, the `packw` instruction with _rs2_=`x0` is the `zext.h` +instruction. +Hence, for RV64, any extension that contains the `packw` instruction also +contains the `zext.h` instruction (but not necessarily the `c.zext.h` +instruction, which is only guaranteed to exist if both the Zcb and Zbb +extensions are implemented). + <<< [#insns-rev8,reftext="Byte-reverse register"] ==== rev8