From: lkcl <lkcl@web>
Date: Sun, 13 Mar 2022 12:43:48 +0000 (+0000)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~3079
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=eadb4e8f85ec0603ae8d16e7c236e13ae9aab24b;p=libreriscv.git

---

diff --git a/openpower/sv/bitmanip.mdwn b/openpower/sv/bitmanip.mdwn
index 71cf2e921..b165dd7ff 100644
--- a/openpower/sv/bitmanip.mdwn
+++ b/openpower/sv/bitmanip.mdwn
@@ -470,19 +470,33 @@ uint64_t unshfl64(uint64_t RA, uint64_t RB)
 
 based on RV bitmanip.
 
-RB contains a vector of indices to select parts of RA to be
-copied to RT.
+RA contains a vector of indices to select parts of RB to be
+copied to RT.  The immediate-variant allows up to an 8 bit
+pattern (repeated) to be targetted at different parts of RT
 
 ```
+uint_xlen_t xpermi(uint8_t imm8, uint_xlen_t RB, int sz_log2)
+{
+    uint_xlen_t r = 0;
+    uint_xlen_t sz = 1LL << sz_log2;
+    uint_xlen_t mask = (1LL << sz) - 1;
+    uint_xlen_t RA = imm8 | imm8<<8 | ... | imm8<<56;
+    for (int i = 0; i < XLEN; i += sz) {
+        uint_xlen_t pos = ((RA >> i) & mask) << sz_log2;
+        if (pos < XLEN)
+            r |= ((RB >> pos) & mask) << i;
+    }
+    return r;
+}
 uint_xlen_t xperm(uint_xlen_t RA, uint_xlen_t RB, int sz_log2)
 {
     uint_xlen_t r = 0;
     uint_xlen_t sz = 1LL << sz_log2;
     uint_xlen_t mask = (1LL << sz) - 1;
     for (int i = 0; i < XLEN; i += sz) {
-        uint_xlen_t pos = ((RB >> i) & mask) << sz_log2;
+        uint_xlen_t pos = ((RA >> i) & mask) << sz_log2;
         if (pos < XLEN)
-            r |= ((RA >> pos) & mask) << i;
+            r |= ((RB >> pos) & mask) << i;
     }
     return r;
 }