From: Andrey Miroshnikov <andrey@technepisteme.xyz>
Date: Tue, 1 Nov 2022 14:49:09 +0000 (+0000)
Subject: ls004: Adjusted word desc based on Lukes c#8, bug #968
X-Git-Tag: opf_rfc_ls005_v1~21
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=2ee653d030e00ffd1e1a93644088e6f2fee59650;p=libreriscv.git

ls004: Adjusted word desc based on Lukes c#8, bug #968
---

diff --git a/openpower/sv/rfc/ls004.mdwn b/openpower/sv/rfc/ls004.mdwn
index 347f27ceb..a8afce0c3 100644
--- a/openpower/sv/rfc/ls004.mdwn
+++ b/openpower/sv/rfc/ls004.mdwn
@@ -96,9 +96,10 @@ Pseudocode:
     sum[0:63] <- ((RB) << shift) + (RA) # Shift RB, add RA
     RT <- sum				            # Result stored in RT
 
-`shift` is determined by the 2-bit bitfield `sm`+1.
-The minimum shift as 1, maximum 4.
-The result is shifted (RB) + (RA), and is stored in register RT.
+When `sm` is zero, the contents of register RB are multiplied by 2,
+added to the contents of register RA, and the result stored in RT.
+
+`sm` is a 2-bit bitfield, and allows multiplication of RB by 2, 4, 8, 16.
 
 Operands RA and RB, and the result RT are all 64-bit, unsigned integers.
 
@@ -120,15 +121,15 @@ shadd r4, r1, r2, 3
 
 Pseudocode:
 
-    shift <- shift + 1			        # Shift is between 1-4
+    shift <- sm + 1			        	# Shift is between 1-4
     n <- (RB)[XLEN/2:XLEN-1] 		    # Limit RB to upper word (32-bits)
     sum[0:63] <- (n << shift) + (RA)    # Shift n, add RA
     RT <- sum				            # Result stored in RT
 
-`shift` is determined by the 2-bit bitfield `sm`+1.
-Mask (RB) to only use the upper word (32-bits).
-The minimum shift as 1, maximum 4.
-The result is shifted `n` + (RA), and is stored in register RT.
+When `sm` is zero, the upper word contents of register RB are multiplied by 2,
+added to the contents of register RA, and the result stored in RT.
+
+`sm` is a 2-bit bitfield, and allows multiplication of RB by 2, 4, 8, 16.
 
 Operands RA and RB, and the result RT are all 64-bit, unsigned integers.