From: lkcl <lkcl@web>
Date: Thu, 19 May 2022 16:09:55 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~2160
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a7c9f8c59c0d8ed1f44be02c1541a5a50f866172;p=libreriscv.git

---

diff --git a/openpower/sv/bitmanip.mdwn b/openpower/sv/bitmanip.mdwn
index b6f53bb00..04c671e55 100644
--- a/openpower/sv/bitmanip.mdwn
+++ b/openpower/sv/bitmanip.mdwn
@@ -97,7 +97,7 @@ TODO: convert all instructions to use RT and not RS
 | NN | RT | RA  |itype/| im0-4   | im5-7  00 |0 | xpermi  | TLI-Form  |
 | NN | RT | RA  | RB   | RC      | nh 00  00 |1 | binlut |  VA-Form      |
 | NN | RT | RA  | RB   | /BFA/   | 0  01  00 |1 | bincrflut  | VA-Form     |
-| NN |    |     |      |         | 1  01  00 |1 | rsvd    |           |
+| NN | RT | RA  | RB   | RC      | 1  01  00 |1 | grevlogr   | VA-Form     |
 | NN |    |     |      |         | -  10  00 |1 | rsvd    |           |
 | NN |    |     |      |         | 0  11  00 |1 | svshape    | SVM-Form    |
 | NN |    |     |      |         | 1  11  00 |1 | svremap   | SVRM-Form   |
@@ -456,7 +456,7 @@ set to the required length:
 
 The following settings provide the required mask constants:
 
-| RA       | RB      | imm        | iv | result        |
+| RA=0     | RB      | imm        | iv | result        |
 | -------  | ------- | ---------- | -- | ----------    |
 | 0x555..  | 0b10    | 0b01101100 | 0  | 0x111111...   |
 | 0x555..  | 0b110   | 0b01101100 | 0  | 0x010101...   |
@@ -499,6 +499,24 @@ uint64_t grevlut(uint64_t RA, uint64_t RB, uint8 imm, bool iv, bool is32b)
         if (shamt & step) x = dorow(imm, x, step, is32b)
     return x;
 }
+```
+
+A 3-register variant may specify different LUT-pairs per row,
+using one byte of RC for each.
+
+```
+uint64_t grevlutr(uint64_t RA, uint64_t RB, uint64_t RC, bool iv, bool is32b)
+{
+    uint64_t x = 0x5555_5555_5555_5555;
+    if (RA != 0) x = GPR(RA);
+    if (iv) x = ~x;
+    int shamt = RB & 31 if is32b else 63
+    for i in 0 to (6-is32b)
+        step = 1<<i
+        imm = (RC>>(i*8))&0xff
+        if (shamt & step) x = dorow(imm, x, step, is32b)
+    return x;
+}
 
 ```