From adbcd27a439b53f1c07e855a938f1db56a8ab04f Mon Sep 17 00:00:00 2001
From: John Winans <john@winans.org>
Date: Fri, 5 Mar 2021 13:53:45 -0600
Subject: [PATCH] Add leading zeros to literals to eliminate sign confusion

---
 book/programs/chapter.tex | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/book/programs/chapter.tex b/book/programs/chapter.tex
index 36b2c49..aac2f5d 100644
--- a/book/programs/chapter.tex
+++ b/book/programs/chapter.tex
@@ -365,26 +365,26 @@ Introduce and present subroutines but not nesting until introduce stack operatio
 {\small
 \begin{verbatim}
     li   rd,constant lui      rd,(constant >>U 12)+(constant & 0x00000800 ? 1 : 0)
-                     addi     rd,rd,(constant & 0xfff)
+                     addi     rd,rd,(constant & 0x00000fff)
 
     la   rd,label
                      auipc    rd,((label-.) >>U 12) + ((label-.) & 0x00000800 ? 1 : 0)
-                     addi     rd,rd,((label-(.-4)) & 0xfff)
+                     addi     rd,rd,((label-(.-4)) & 0x00000fff)
 
     l{b|h|w} rd,label
                      auipc    rd,((label-.) >>U 12) + ((label-.) & 0x00000800 ? 1 : 0)
-                     l{b|h|w} rd,((label-(.-4)) & 0xfff)(rd)
+                     l{b|h|w} rd,((label-(.-4)) & 0x00000fff)(rd)
 
     s{b|h|w} rd,label,rt               # rt used as a temp reg for the operation (default=x6)
                      auipc    rt,((label-.) >>U 12) + ((label-.) & 0x00000800 ? 1 : 0)
-                     s{b|h|w} rd,((label-(.-4)) & 0xfff)(rt)
+                     s{b|h|w} rd,((label-(.-4)) & 0x00000fff)(rt)
 
     call label       auipc    x1,((label-.) >>U 12) + ((label-.) & 0x00000800 ? 1 : 0)
-                     jalr     x1,((label-(.-4)) & 0xfff)(x1)
+                     jalr     x1,((label-(.-4)) & 0x00000fff)(x1)
 
     tail label,rt                      # rt used as a temp reg for the operation (default=x6)
                      auipc    rt,((label-.) >>U 12) + ((label-.) & 0x00000800 ? 1 : 0)
-                     jalr     x0,((label-(.-4)) & 0xfff)(rt)
+                     jalr     x0,((label-(.-4)) & 0x00000fff)(rt)
 
     mv   rd,rs       addi     rd,rs,0
  
@@ -427,7 +427,7 @@ To remedy this problem, the value used in the {\tt lui} instruction can altered
 instruction:
 {\small
 \begin{verbatim}
-    lui  x5,0x12346    // x5 = 0x12346000  (note this is 0x12345 + 1)
+    lui  x5,0x12346    // x5 = 0x12346000  (note: this is 0x12345000 + 0x1000)
     addi x5,x5,0x800   // x5 = 0x12346000 + sx(0x800) = 0x12346000 + 0xfffff800 = 0x12345800
 \end{verbatim}
 }
@@ -481,7 +481,7 @@ The \verb@la@ instruction here will expand into:
 {\small
 \begin{verbatim}
 00010040     auipc x10,((var1-.) >>U 12) + ((var1-.) & 0x00000800 ? 1 : 0)
-00010044     addi  x10,x10,((var1-(.-4)) & 0xfff)
+00010044     addi  x10,x10,((var1-(.-4)) & 0x00000fff)
 \end{verbatim}
 }
 
@@ -498,14 +498,14 @@ Therefore the expanded pseudoinstruction example will become:
 {\small
 \begin{verbatim}
 00010040     auipc x10,((0x00010900-0x00010040) >>U 12) + ((0x00010900-0x00010040) & 0x00000800 ? 1 : 0)
-00010044     addi  x10,x10,((0x00010900-(0x00010044-4)) & 0xfff)      # note the extra -4 here!
+00010044     addi  x10,x10,((0x00010900-(0x00010044-4)) & 0x00000fff)      # note the extra -4 here!
 \end{verbatim}
 }
 After performing the subtractions, it will reduce to this:
 {\small
 \begin{verbatim}
 00010040     auipc x10,(0x000008c0 >>U 12) + ((0x000008c0) & 0x00000800 ? 1 : 0)
-00010044     addi  x10,x10,(0x000008c0 & 0xfff)
+00010044     addi  x10,x10,(0x000008c0 & 0x00000fff)
 \end{verbatim}
 }
 Continuing to reduce the math operations we get:
@@ -546,7 +546,7 @@ To refer to an absolute value, the following operators can be used:
 {\small
 \begin{verbatim}
     %hi(constant)    // becomes: (constant >>U 12)+(constant & 0x00000800 ? 1 : 0)
-    %lo(constant)    // becomes: (constant & 0xfff)
+    %lo(constant)    // becomes: (constant & 0x00000fff)
 \end{verbatim}
 }
 
@@ -567,7 +567,7 @@ The following can be used for PC-relative addresses:
 {\small
 \begin{verbatim}
     %pcrel_hi(symbol) // becomes: ((symbol-.) >>U 12) + ((symbol-.) & 0x00000800 ? 1 : 0)
-    %pcrel_lo(lab)    // becomes: ((symbol-lab) & 0xfff)
+    %pcrel_lo(lab)    // becomes: ((symbol-lab) & 0x00000fff)
 \end{verbatim}
 }
 
@@ -590,7 +590,7 @@ Examples of using the \verb@auipc@ \& \verb@addi@ together with \verb@%pcrel_hi(
 {\small
 \begin{verbatim}
 xxx:    auipc   t1,%pcrel_hi(yyy)     // (yyy-xxx) >>U 12) + ((yyy-xxx) & 0x00000800 ? 1 : 0)
-        addi    t1,t1,%pcrel_lo(xxx)  // ((yyy-xxx) & 0xfff)
+        addi    t1,t1,%pcrel_lo(xxx)  // ((yyy-xxx) & 0x00000fff)
 ...
 yyy:                                  // the address: yyy is saved into t1 above
 ...