From: Jacob Lifshay <programmerjake@gmail.com>
Date: Mon, 13 Mar 2023 23:40:35 +0000 (-0700)
Subject: add binlog to ls007
X-Git-Tag: opf_rfc_ls001_v3~177
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=45bf4930aec86ac11b2773421a315ec3e560f68e;p=libreriscv.git

add binlog to ls007
---

diff --git a/openpower/sv/rfc/ls007.mdwn b/openpower/sv/rfc/ls007.mdwn
index b35d4cbf0..1c1113318 100644
--- a/openpower/sv/rfc/ls007.mdwn
+++ b/openpower/sv/rfc/ls007.mdwn
@@ -103,6 +103,15 @@ Add the following section to Book I 1.6.1
 | PO | RT | RA | RB | TLI | XO | Rc |
 ```
 
+# VA-FORM
+
+Add the following entry to VA-FORM in Book I 1.6.1.12
+
+```
+|0      |6     |11     |16     |21|22    |26|27   |
+| PO    |  RT  |   RA  |   RB  |   RC    |nh| XO  |
+```
+
 # Word Instruction Fields
 
 Add the following to Book I 1.6.2
@@ -113,6 +122,13 @@ msk (18:20, 31)
     Formats: CRB
 ```
 
+```
+nh (26)
+    Nibble High. Field used by binlog to decide if the look-up-table should
+    be taken from bits 60:63 or 56:59 of RC.
+    Formats: VA
+```
+
 ```
 TLI (21:28)
     Field used by the ternlogi instruction as the
@@ -128,6 +144,11 @@ XO (29:30)
 
 Add `TLI` to the `Formats:` list of all of `RA`, `RB`, `RT`, and `Rc`.
 Add `CRB` to the `Formats:` list of all of `BF`, `BFA`, `BFB`, and `BFC`.
+Add `VA` to the `Formats:` list of `XO (27:31)`.
+
+----------
+
+\newpage{}
 
 # Ternary Logic Immediate TLI-form
 
@@ -158,6 +179,51 @@ CR0                    (if Rc=1)
 
 \newpage{}
 
+# Dynamic Binary Logic VA-form
+
+* `binlog RT, RA, RB, RC, nh`
+
+| 0-5 | 6-10 | 11-15 | 16-20 | 21-25 | 26 | 27-31 | Form    |
+|-----|------|-------|-------|-------|----|-------|---------|
+| PO  |  RT  |  RA   |  RB   |  RC   | nh | XO    | VA-Form |
+
+Pseudocode:
+
+```
+if nh = 1 then
+    lut <- (RC)[56:59]
+else
+    lut <- (RC)[60:63]
+do i = 0 to 63
+    idx <- (RB)[i] || (RA)[i]  # compute index from current bits
+    result[i] <- lut[3 - idx]  # subtract from 3 to index in LSB0 order
+RT <- result
+```
+
+Special registers altered:
+
+```
+None
+```
+
+**Programming Note**:
+
+Dynamic Ternary Logic may be emulated by appropriate combination of `binlog` and `ternlogi`:
+
+```
+# compute r3 = ternlog(r4, r5, r6, table=r7)
+# compute the values for when r6[i] = 0:
+binlog r3, r4, r5, r7, 0  # takes look-up-table from LSB 4 bits
+# compute the values for when r6[i] = 1:
+binlog r4, r4, r5, r7, 1  # takes look-up-table from second-to-LSB 4 bits
+# mux the two results together: r3 = (r3 & ~r6) | (r4 & r6)
+ternlogi r3, r4, r6, 0b11011000
+```
+
+----------
+
+\newpage{}
+
 
 ----------