From: lkcl <lkcl@web>
Date: Thu, 20 Oct 2022 21:52:32 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~68
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d049e34a75e673ccdcbab7fc752020d71ea736fc;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls003.mdwn b/openpower/sv/rfc/ls003.mdwn
index a43cfe676..042f942b7 100644
--- a/openpower/sv/rfc/ls003.mdwn
+++ b/openpower/sv/rfc/ls003.mdwn
@@ -101,7 +101,7 @@ Pseudocode:
     prod[0:127] <- (RA) * (RB)	  # Multiply RA and RB, result 128-bit
     sum[0:127] <- EXTZ(RC) + prod # Zero extend RC, add product
     RT <- sum[64:127]		  # Store low half in RT
-    RS <- sum[0:63] 		  # RS implicit register, see below
+    RS <- sum[0:63] 		  # RS implicit register, equal to RC
 ```
 
 Special registers altered:
@@ -120,7 +120,7 @@ performing sign-extension on RC, because RT is the full mathematical result
 modulo 2^64 and sign/zero extension from 64 to 128 bits produces identical
 results modulo 2^64. This is why there is no maddldu instruction.
 
-RS is implictly defined as the register following RT (RS=RT+1).
+RS is implictly defined as the same register as RC.
 
 *Programmer's Note:
 As a Scalar Power ISA operation, like `lq` and `stq`, RS=RT+1.
@@ -137,7 +137,8 @@ as Scalar GPR register file space permits.*
 Examples:
 
 ```
-    maddedu r4, r0, r1, r2 # ((r0)*(r1))+(r2), store lower in r4, upper in r5
+# (r0 * r1) + r2, store lower in r4, upper in r2
+maddedu r4, r0, r1, r2
 ```
 
 # Divide/Modulo Quad-Double Unsigned
@@ -191,13 +192,13 @@ been set to useful values (all 1s and all zeros respectively)
 needed as part of implementing Knuth's
 Algorithm D*
 
-For Scalar usage, just as for `maddedu`, `RS=RT+1` (similar to `lq` and `stq`).
-
+For Scalar usage, just as for `maddedu`, `RS=RC`
 Examples:
 
 ```
-    divmod2du r4, r0, r1, r2 # ((r0)||(r2)) / (r1), store in r4
-    			     # ((r0)||(r2)) % (r1), store in r5
+# ((r0 << 64) + r2) / r1, store in r4
+# ((r0 << 64) + r2) % r1, store in r2
+divmod2du r4, r0, r1, r2
 ```
 
 [[!tag opf_rfc]]