From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Fri, 1 Jul 2022 15:15:21 +0000 (+0100)
Subject: clarify swizzle pseudocode in overview
X-Git-Tag: opf_rfc_ls005_v1~1419
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=4f524730305ba11c7b034b68156f31b41c8ca427;p=libreriscv.git

clarify swizzle pseudocode in overview
---

diff --git a/openpower/sv/overview.mdwn b/openpower/sv/overview.mdwn
index 24f1ec7f4..804d7042a 100644
--- a/openpower/sv/overview.mdwn
+++ b/openpower/sv/overview.mdwn
@@ -729,13 +729,13 @@ those:
     swizzle = get_swizzle_immed() # 12 bits
     for (s = 0; s < SUBVL; s++)
         remap = (swizzle >> 3*s) & 0b111
-        if remap < 4:
-           sm = id*SUBVL + remap
+        if remap == 0b000: continue            # skip
+        if remap == 0b001: break               # end marker
+        if remap == 0b010: ireg[rd+s] <= 0.0   # constant 0
+        elif remap == 0b011: ireg[rd+s] <= 1.0 # constant 1
+        else:                                  # XYZW
+           sm = id*SUBVL + (remap-4)
            ireg[rd+s] <= ireg[RA+sm]
-        elif remap == 4:
-              ireg[rd+s] <= 0.0
-        elif remap == 5:
-              ireg[rd+s] <= 1.0
 
 Note that a value of 6 (and 7) will leave the target subvector element
 untouched. This is equivalent to a predicate mask which is built-in,