From aaab515b5a9d8dc6eb19e6bb4330012bdffff4fb Mon Sep 17 00:00:00 2001
From: John Winans <john@winans.org>
Date: Thu, 12 Mar 2020 14:16:29 -0500
Subject: [PATCH] Express shamt_i in terms of XLEN.

---
 book/refcard/chapter.tex | 6 +++---
 book/rv32/chapter.tex    | 8 +++++---
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/book/refcard/chapter.tex b/book/refcard/chapter.tex
index f0ea8d5..01e3e1b 100644
--- a/book/refcard/chapter.tex
+++ b/book/refcard/chapter.tex
@@ -54,7 +54,7 @@ sb    & rs2, imm(rs1) & \hyperref[insnformat:stype]{S} & \hyperref[insn:sb]{Stor
 \hline
 sh    & rs2, imm(rs1) & \hyperref[insnformat:stype]{S} & \hyperref[insn:sh]{Store Halfword}              & {\tt m16(rs1+\hyperref[imm.s:decode]{imm\_s}) $\leftarrow$ rs2[15:0], pc $\leftarrow$ pc+4}\\
 \hline
-sll   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:sll]{Shift Left Logical}        & {\tt rd $\leftarrow$ rs1 << (rs2\&0x1f), pc $\leftarrow$ pc+4}\\
+sll   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:sll]{Shift Left Logical}        & {\tt rd $\leftarrow$ rs1 << (rs2\%XLEN), pc $\leftarrow$ pc+4}\\
 \hline
 slli  & rd, rs1, shamt & \hyperref[insnformat:itype]{I} & \hyperref[insn:slli]{Shift Left Logical Immediate} & {\tt rd $\leftarrow$ rs1 << \hyperref[shamt.i:decode]{shamt\_i}, pc $\leftarrow$ pc+4}\\
 \hline
@@ -66,11 +66,11 @@ sltiu & rd, rs1, imm  & \hyperref[insnformat:itype]{I} & \hyperref[insn:sltiu]{S
 \hline
 sltu  & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:sltu]{Set Less Than Unsigned}   & {\tt rd $\leftarrow$ (rs1 < rs2) ? 1 : 0, pc $\leftarrow$ pc+4}\\
 \hline
-sra   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:sra]{Shift Right Arithmetic}    & {\tt rd $\leftarrow$ rs1 >> (rs2\&0x1f), pc $\leftarrow$ pc+4}\\
+sra   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:sra]{Shift Right Arithmetic}    & {\tt rd $\leftarrow$ rs1 >> (rs2\%XLEN), pc $\leftarrow$ pc+4}\\
 \hline
 srai  & rd, rs1, shamt & \hyperref[insnformat:itype]{I} & \hyperref[insn:srai]{Shift Right Arithmetic Immediate} & {\tt rd $\leftarrow$ rs1 >> \hyperref[shamt.i:decode]{shamt\_i}, pc $\leftarrow$ pc+4}\\
 \hline
-srl   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:srl]{Shift Right Logical}       & {\tt rd $\leftarrow$ rs1 >> (rs2\&0x1f), pc $\leftarrow$ pc+4}\\
+srl   & rd, rs1, rs2   & \hyperref[insnformat:rtype]{R} & \hyperref[insn:srl]{Shift Right Logical}       & {\tt rd $\leftarrow$ rs1 >> (rs2\%XLEN), pc $\leftarrow$ pc+4}\\
 \hline
 srli  & rd, rs1, shamt & \hyperref[insnformat:itype]{I} & \hyperref[insn:srli]{Shift Right Logical Immediate} & {\tt rd $\leftarrow$ rs1 >> \hyperref[shamt.i:decode]{shamt\_i}, pc $\leftarrow$ pc+4}\\
 \hline
diff --git a/book/rv32/chapter.tex b/book/rv32/chapter.tex
index a9c43ea..d928c53 100644
--- a/book/rv32/chapter.tex
+++ b/book/rv32/chapter.tex
@@ -622,10 +622,12 @@ to form the \verb@imm_i@ value.
 \end{figure}
 
 A special case of the I-type is used for shift-immediate instructions 
-where only five bits of the imm field are used to represent the number 
-of bit positions to shift as shown in \autoref{Figure:shamt_i_type_decode}. 
+where the imm field is used to represent the number of bit positions 
+to shift as shown in \autoref{Figure:shamt_i_type_decode}.
 In this variation, the least significant five bits of the imm field are 
-zero-extended to form the \verb@shamt_i@ value.
+zero-extended to form the \verb@shamt_i@ 
+value.\footnote{When XLEN is 64 or 128, the {\tt shamt\_i} field will 
+consist of 6 or 7 bits respectively.}
 
 \begin{figure}[ht]
 \centering