-
Notifications
You must be signed in to change notification settings - Fork 2
/
Copy pathriscv_book.html
6657 lines (6383 loc) · 347 KB
/
riscv_book.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 2.0.20">
<meta name="author" content="Robert Winkler">
<title>RISC-V Assembly Programmming</title>
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700">
<style>
/*! Asciidoctor default stylesheet | MIT License | https://asciidoctor.org */
/* Uncomment the following line when using as a custom stylesheet */
/* @import "https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700"; */
html{font-family:sans-serif;-webkit-text-size-adjust:100%}
a{background:none}
a:focus{outline:thin dotted}
a:active,a:hover{outline:0}
h1{font-size:2em;margin:.67em 0}
b,strong{font-weight:bold}
abbr{font-size:.9em}
abbr[title]{cursor:help;border-bottom:1px dotted #dddddf;text-decoration:none}
dfn{font-style:italic}
hr{height:0}
mark{background:#ff0;color:#000}
code,kbd,pre,samp{font-family:monospace;font-size:1em}
pre{white-space:pre-wrap}
q{quotes:"\201C" "\201D" "\2018" "\2019"}
small{font-size:80%}
sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}
sup{top:-.5em}
sub{bottom:-.25em}
img{border:0}
svg:not(:root){overflow:hidden}
figure{margin:0}
audio,video{display:inline-block}
audio:not([controls]){display:none;height:0}
fieldset{border:1px solid silver;margin:0 2px;padding:.35em .625em .75em}
legend{border:0;padding:0}
button,input,select,textarea{font-family:inherit;font-size:100%;margin:0}
button,input{line-height:normal}
button,select{text-transform:none}
button,html input[type=button],input[type=reset],input[type=submit]{-webkit-appearance:button;cursor:pointer}
button[disabled],html input[disabled]{cursor:default}
input[type=checkbox],input[type=radio]{padding:0}
button::-moz-focus-inner,input::-moz-focus-inner{border:0;padding:0}
textarea{overflow:auto;vertical-align:top}
table{border-collapse:collapse;border-spacing:0}
*,::before,::after{box-sizing:border-box}
html,body{font-size:100%}
body{background:#fff;color:rgba(0,0,0,.8);padding:0;margin:0;font-family:"Noto Serif","DejaVu Serif",serif;line-height:1;position:relative;cursor:auto;-moz-tab-size:4;-o-tab-size:4;tab-size:4;word-wrap:anywhere;-moz-osx-font-smoothing:grayscale;-webkit-font-smoothing:antialiased}
a:hover{cursor:pointer}
img,object,embed{max-width:100%;height:auto}
object,embed{height:100%}
img{-ms-interpolation-mode:bicubic}
.left{float:left!important}
.right{float:right!important}
.text-left{text-align:left!important}
.text-right{text-align:right!important}
.text-center{text-align:center!important}
.text-justify{text-align:justify!important}
.hide{display:none}
img,object,svg{display:inline-block;vertical-align:middle}
textarea{height:auto;min-height:50px}
select{width:100%}
.subheader,.admonitionblock td.content>.title,.audioblock>.title,.exampleblock>.title,.imageblock>.title,.listingblock>.title,.literalblock>.title,.stemblock>.title,.openblock>.title,.paragraph>.title,.quoteblock>.title,table.tableblock>.title,.verseblock>.title,.videoblock>.title,.dlist>.title,.olist>.title,.ulist>.title,.qlist>.title,.hdlist>.title{line-height:1.45;color:#7a2518;font-weight:400;margin-top:0;margin-bottom:.25em}
div,dl,dt,dd,ul,ol,li,h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6,pre,form,p,blockquote,th,td{margin:0;padding:0}
a{color:#2156a5;text-decoration:underline;line-height:inherit}
a:hover,a:focus{color:#1d4b8f}
a img{border:0}
p{line-height:1.6;margin-bottom:1.25em;text-rendering:optimizeLegibility}
p aside{font-size:.875em;line-height:1.35;font-style:italic}
h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{font-family:"Open Sans","DejaVu Sans",sans-serif;font-weight:300;font-style:normal;color:#ba3925;text-rendering:optimizeLegibility;margin-top:1em;margin-bottom:.5em;line-height:1.0125em}
h1 small,h2 small,h3 small,#toctitle small,.sidebarblock>.content>.title small,h4 small,h5 small,h6 small{font-size:60%;color:#e99b8f;line-height:0}
h1{font-size:2.125em}
h2{font-size:1.6875em}
h3,#toctitle,.sidebarblock>.content>.title{font-size:1.375em}
h4,h5{font-size:1.125em}
h6{font-size:1em}
hr{border:solid #dddddf;border-width:1px 0 0;clear:both;margin:1.25em 0 1.1875em}
em,i{font-style:italic;line-height:inherit}
strong,b{font-weight:bold;line-height:inherit}
small{font-size:60%;line-height:inherit}
code{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;font-weight:400;color:rgba(0,0,0,.9)}
ul,ol,dl{line-height:1.6;margin-bottom:1.25em;list-style-position:outside;font-family:inherit}
ul,ol{margin-left:1.5em}
ul li ul,ul li ol{margin-left:1.25em;margin-bottom:0}
ul.circle{list-style-type:circle}
ul.disc{list-style-type:disc}
ul.square{list-style-type:square}
ul.circle ul:not([class]),ul.disc ul:not([class]),ul.square ul:not([class]){list-style:inherit}
ol li ul,ol li ol{margin-left:1.25em;margin-bottom:0}
dl dt{margin-bottom:.3125em;font-weight:bold}
dl dd{margin-bottom:1.25em}
blockquote{margin:0 0 1.25em;padding:.5625em 1.25em 0 1.1875em;border-left:1px solid #ddd}
blockquote,blockquote p{line-height:1.6;color:rgba(0,0,0,.85)}
@media screen and (min-width:768px){h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{line-height:1.2}
h1{font-size:2.75em}
h2{font-size:2.3125em}
h3,#toctitle,.sidebarblock>.content>.title{font-size:1.6875em}
h4{font-size:1.4375em}}
table{background:#fff;margin-bottom:1.25em;border:1px solid #dedede;word-wrap:normal}
table thead,table tfoot{background:#f7f8f7}
table thead tr th,table thead tr td,table tfoot tr th,table tfoot tr td{padding:.5em .625em .625em;font-size:inherit;color:rgba(0,0,0,.8);text-align:left}
table tr th,table tr td{padding:.5625em .625em;font-size:inherit;color:rgba(0,0,0,.8)}
table tr.even,table tr.alt{background:#f8f8f7}
table thead tr th,table tfoot tr th,table tbody tr td,table tr td,table tfoot tr td{line-height:1.6}
h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{line-height:1.2;word-spacing:-.05em}
h1 strong,h2 strong,h3 strong,#toctitle strong,.sidebarblock>.content>.title strong,h4 strong,h5 strong,h6 strong{font-weight:400}
.center{margin-left:auto;margin-right:auto}
.stretch{width:100%}
.clearfix::before,.clearfix::after,.float-group::before,.float-group::after{content:" ";display:table}
.clearfix::after,.float-group::after{clear:both}
:not(pre).nobreak{word-wrap:normal}
:not(pre).nowrap{white-space:nowrap}
:not(pre).pre-wrap{white-space:pre-wrap}
:not(pre):not([class^=L])>code{font-size:.9375em;font-style:normal!important;letter-spacing:0;padding:.1em .5ex;word-spacing:-.15em;background:#f7f7f8;border-radius:4px;line-height:1.45;text-rendering:optimizeSpeed}
pre{color:rgba(0,0,0,.9);font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;line-height:1.45;text-rendering:optimizeSpeed}
pre code,pre pre{color:inherit;font-size:inherit;line-height:inherit}
pre>code{display:block}
pre.nowrap,pre.nowrap pre{white-space:pre;word-wrap:normal}
em em{font-style:normal}
strong strong{font-weight:400}
.keyseq{color:rgba(51,51,51,.8)}
kbd{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;display:inline-block;color:rgba(0,0,0,.8);font-size:.65em;line-height:1.45;background:#f7f7f7;border:1px solid #ccc;border-radius:3px;box-shadow:0 1px 0 rgba(0,0,0,.2),inset 0 0 0 .1em #fff;margin:0 .15em;padding:.2em .5em;vertical-align:middle;position:relative;top:-.1em;white-space:nowrap}
.keyseq kbd:first-child{margin-left:0}
.keyseq kbd:last-child{margin-right:0}
.menuseq,.menuref{color:#000}
.menuseq b:not(.caret),.menuref{font-weight:inherit}
.menuseq{word-spacing:-.02em}
.menuseq b.caret{font-size:1.25em;line-height:.8}
.menuseq i.caret{font-weight:bold;text-align:center;width:.45em}
b.button::before,b.button::after{position:relative;top:-1px;font-weight:400}
b.button::before{content:"[";padding:0 3px 0 2px}
b.button::after{content:"]";padding:0 2px 0 3px}
p a>code:hover{color:rgba(0,0,0,.9)}
#header,#content,#footnotes,#footer{width:100%;margin:0 auto;max-width:62.5em;*zoom:1;position:relative;padding-left:.9375em;padding-right:.9375em}
#header::before,#header::after,#content::before,#content::after,#footnotes::before,#footnotes::after,#footer::before,#footer::after{content:" ";display:table}
#header::after,#content::after,#footnotes::after,#footer::after{clear:both}
#content{margin-top:1.25em}
#content::before{content:none}
#header>h1:first-child{color:rgba(0,0,0,.85);margin-top:2.25rem;margin-bottom:0}
#header>h1:first-child+#toc{margin-top:8px;border-top:1px solid #dddddf}
#header>h1:only-child,body.toc2 #header>h1:nth-last-child(2){border-bottom:1px solid #dddddf;padding-bottom:8px}
#header .details{border-bottom:1px solid #dddddf;line-height:1.45;padding-top:.25em;padding-bottom:.25em;padding-left:.25em;color:rgba(0,0,0,.6);display:flex;flex-flow:row wrap}
#header .details span:first-child{margin-left:-.125em}
#header .details span.email a{color:rgba(0,0,0,.85)}
#header .details br{display:none}
#header .details br+span::before{content:"\00a0\2013\00a0"}
#header .details br+span.author::before{content:"\00a0\22c5\00a0";color:rgba(0,0,0,.85)}
#header .details br+span#revremark::before{content:"\00a0|\00a0"}
#header #revnumber{text-transform:capitalize}
#header #revnumber::after{content:"\00a0"}
#content>h1:first-child:not([class]){color:rgba(0,0,0,.85);border-bottom:1px solid #dddddf;padding-bottom:8px;margin-top:0;padding-top:1rem;margin-bottom:1.25rem}
#toc{border-bottom:1px solid #e7e7e9;padding-bottom:.5em}
#toc>ul{margin-left:.125em}
#toc ul.sectlevel0>li>a{font-style:italic}
#toc ul.sectlevel0 ul.sectlevel1{margin:.5em 0}
#toc ul{font-family:"Open Sans","DejaVu Sans",sans-serif;list-style-type:none}
#toc li{line-height:1.3334;margin-top:.3334em}
#toc a{text-decoration:none}
#toc a:active{text-decoration:underline}
#toctitle{color:#7a2518;font-size:1.2em}
@media screen and (min-width:768px){#toctitle{font-size:1.375em}
body.toc2{padding-left:15em;padding-right:0}
#toc.toc2{margin-top:0!important;background:#f8f8f7;position:fixed;width:15em;left:0;top:0;border-right:1px solid #e7e7e9;border-top-width:0!important;border-bottom-width:0!important;z-index:1000;padding:1.25em 1em;height:100%;overflow:auto}
#toc.toc2 #toctitle{margin-top:0;margin-bottom:.8rem;font-size:1.2em}
#toc.toc2>ul{font-size:.9em;margin-bottom:0}
#toc.toc2 ul ul{margin-left:0;padding-left:1em}
#toc.toc2 ul.sectlevel0 ul.sectlevel1{padding-left:0;margin-top:.5em;margin-bottom:.5em}
body.toc2.toc-right{padding-left:0;padding-right:15em}
body.toc2.toc-right #toc.toc2{border-right-width:0;border-left:1px solid #e7e7e9;left:auto;right:0}}
@media screen and (min-width:1280px){body.toc2{padding-left:20em;padding-right:0}
#toc.toc2{width:20em}
#toc.toc2 #toctitle{font-size:1.375em}
#toc.toc2>ul{font-size:.95em}
#toc.toc2 ul ul{padding-left:1.25em}
body.toc2.toc-right{padding-left:0;padding-right:20em}}
#content #toc{border:1px solid #e0e0dc;margin-bottom:1.25em;padding:1.25em;background:#f8f8f7;border-radius:4px}
#content #toc>:first-child{margin-top:0}
#content #toc>:last-child{margin-bottom:0}
#footer{max-width:none;background:rgba(0,0,0,.8);padding:1.25em}
#footer-text{color:hsla(0,0%,100%,.8);line-height:1.44}
#content{margin-bottom:.625em}
.sect1{padding-bottom:.625em}
@media screen and (min-width:768px){#content{margin-bottom:1.25em}
.sect1{padding-bottom:1.25em}}
.sect1:last-child{padding-bottom:0}
.sect1+.sect1{border-top:1px solid #e7e7e9}
#content h1>a.anchor,h2>a.anchor,h3>a.anchor,#toctitle>a.anchor,.sidebarblock>.content>.title>a.anchor,h4>a.anchor,h5>a.anchor,h6>a.anchor{position:absolute;z-index:1001;width:1.5ex;margin-left:-1.5ex;display:block;text-decoration:none!important;visibility:hidden;text-align:center;font-weight:400}
#content h1>a.anchor::before,h2>a.anchor::before,h3>a.anchor::before,#toctitle>a.anchor::before,.sidebarblock>.content>.title>a.anchor::before,h4>a.anchor::before,h5>a.anchor::before,h6>a.anchor::before{content:"\00A7";font-size:.85em;display:block;padding-top:.1em}
#content h1:hover>a.anchor,#content h1>a.anchor:hover,h2:hover>a.anchor,h2>a.anchor:hover,h3:hover>a.anchor,#toctitle:hover>a.anchor,.sidebarblock>.content>.title:hover>a.anchor,h3>a.anchor:hover,#toctitle>a.anchor:hover,.sidebarblock>.content>.title>a.anchor:hover,h4:hover>a.anchor,h4>a.anchor:hover,h5:hover>a.anchor,h5>a.anchor:hover,h6:hover>a.anchor,h6>a.anchor:hover{visibility:visible}
#content h1>a.link,h2>a.link,h3>a.link,#toctitle>a.link,.sidebarblock>.content>.title>a.link,h4>a.link,h5>a.link,h6>a.link{color:#ba3925;text-decoration:none}
#content h1>a.link:hover,h2>a.link:hover,h3>a.link:hover,#toctitle>a.link:hover,.sidebarblock>.content>.title>a.link:hover,h4>a.link:hover,h5>a.link:hover,h6>a.link:hover{color:#a53221}
details,.audioblock,.imageblock,.literalblock,.listingblock,.stemblock,.videoblock{margin-bottom:1.25em}
details{margin-left:1.25rem}
details>summary{cursor:pointer;display:block;position:relative;line-height:1.6;margin-bottom:.625rem;outline:none;-webkit-tap-highlight-color:transparent}
details>summary::-webkit-details-marker{display:none}
details>summary::before{content:"";border:solid transparent;border-left:solid;border-width:.3em 0 .3em .5em;position:absolute;top:.5em;left:-1.25rem;transform:translateX(15%)}
details[open]>summary::before{border:solid transparent;border-top:solid;border-width:.5em .3em 0;transform:translateY(15%)}
details>summary::after{content:"";width:1.25rem;height:1em;position:absolute;top:.3em;left:-1.25rem}
.admonitionblock td.content>.title,.audioblock>.title,.exampleblock>.title,.imageblock>.title,.listingblock>.title,.literalblock>.title,.stemblock>.title,.openblock>.title,.paragraph>.title,.quoteblock>.title,table.tableblock>.title,.verseblock>.title,.videoblock>.title,.dlist>.title,.olist>.title,.ulist>.title,.qlist>.title,.hdlist>.title{text-rendering:optimizeLegibility;text-align:left;font-family:"Noto Serif","DejaVu Serif",serif;font-size:1rem;font-style:italic}
table.tableblock.fit-content>caption.title{white-space:nowrap;width:0}
.paragraph.lead>p,#preamble>.sectionbody>[class=paragraph]:first-of-type p{font-size:1.21875em;line-height:1.6;color:rgba(0,0,0,.85)}
.admonitionblock>table{border-collapse:separate;border:0;background:none;width:100%}
.admonitionblock>table td.icon{text-align:center;width:80px}
.admonitionblock>table td.icon img{max-width:none}
.admonitionblock>table td.icon .title{font-weight:bold;font-family:"Open Sans","DejaVu Sans",sans-serif;text-transform:uppercase}
.admonitionblock>table td.content{padding-left:1.125em;padding-right:1.25em;border-left:1px solid #dddddf;color:rgba(0,0,0,.6);word-wrap:anywhere}
.admonitionblock>table td.content>:last-child>:last-child{margin-bottom:0}
.exampleblock>.content{border:1px solid #e6e6e6;margin-bottom:1.25em;padding:1.25em;background:#fff;border-radius:4px}
.sidebarblock{border:1px solid #dbdbd6;margin-bottom:1.25em;padding:1.25em;background:#f3f3f2;border-radius:4px}
.sidebarblock>.content>.title{color:#7a2518;margin-top:0;text-align:center}
.exampleblock>.content>:first-child,.sidebarblock>.content>:first-child{margin-top:0}
.exampleblock>.content>:last-child,.exampleblock>.content>:last-child>:last-child,.exampleblock>.content .olist>ol>li:last-child>:last-child,.exampleblock>.content .ulist>ul>li:last-child>:last-child,.exampleblock>.content .qlist>ol>li:last-child>:last-child,.sidebarblock>.content>:last-child,.sidebarblock>.content>:last-child>:last-child,.sidebarblock>.content .olist>ol>li:last-child>:last-child,.sidebarblock>.content .ulist>ul>li:last-child>:last-child,.sidebarblock>.content .qlist>ol>li:last-child>:last-child{margin-bottom:0}
.literalblock pre,.listingblock>.content>pre{border-radius:4px;overflow-x:auto;padding:1em;font-size:.8125em}
@media screen and (min-width:768px){.literalblock pre,.listingblock>.content>pre{font-size:.90625em}}
@media screen and (min-width:1280px){.literalblock pre,.listingblock>.content>pre{font-size:1em}}
.literalblock pre,.listingblock>.content>pre:not(.highlight),.listingblock>.content>pre[class=highlight],.listingblock>.content>pre[class^="highlight "]{background:#f7f7f8}
.literalblock.output pre{color:#f7f7f8;background:rgba(0,0,0,.9)}
.listingblock>.content{position:relative}
.listingblock code[data-lang]::before{display:none;content:attr(data-lang);position:absolute;font-size:.75em;top:.425rem;right:.5rem;line-height:1;text-transform:uppercase;color:inherit;opacity:.5}
.listingblock:hover code[data-lang]::before{display:block}
.listingblock.terminal pre .command::before{content:attr(data-prompt);padding-right:.5em;color:inherit;opacity:.5}
.listingblock.terminal pre .command:not([data-prompt])::before{content:"$"}
.listingblock pre.highlightjs{padding:0}
.listingblock pre.highlightjs>code{padding:1em;border-radius:4px}
.listingblock pre.prettyprint{border-width:0}
.prettyprint{background:#f7f7f8}
pre.prettyprint .linenums{line-height:1.45;margin-left:2em}
pre.prettyprint li{background:none;list-style-type:inherit;padding-left:0}
pre.prettyprint li code[data-lang]::before{opacity:1}
pre.prettyprint li:not(:first-child) code[data-lang]::before{display:none}
table.linenotable{border-collapse:separate;border:0;margin-bottom:0;background:none}
table.linenotable td[class]{color:inherit;vertical-align:top;padding:0;line-height:inherit;white-space:normal}
table.linenotable td.code{padding-left:.75em}
table.linenotable td.linenos,pre.pygments .linenos{border-right:1px solid;opacity:.35;padding-right:.5em;-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none}
pre.pygments span.linenos{display:inline-block;margin-right:.75em}
.quoteblock{margin:0 1em 1.25em 1.5em;display:table}
.quoteblock:not(.excerpt)>.title{margin-left:-1.5em;margin-bottom:.75em}
.quoteblock blockquote,.quoteblock p{color:rgba(0,0,0,.85);font-size:1.15rem;line-height:1.75;word-spacing:.1em;letter-spacing:0;font-style:italic;text-align:justify}
.quoteblock blockquote{margin:0;padding:0;border:0}
.quoteblock blockquote::before{content:"\201c";float:left;font-size:2.75em;font-weight:bold;line-height:.6em;margin-left:-.6em;color:#7a2518;text-shadow:0 1px 2px rgba(0,0,0,.1)}
.quoteblock blockquote>.paragraph:last-child p{margin-bottom:0}
.quoteblock .attribution{margin-top:.75em;margin-right:.5ex;text-align:right}
.verseblock{margin:0 1em 1.25em}
.verseblock pre{font-family:"Open Sans","DejaVu Sans",sans-serif;font-size:1.15rem;color:rgba(0,0,0,.85);font-weight:300;text-rendering:optimizeLegibility}
.verseblock pre strong{font-weight:400}
.verseblock .attribution{margin-top:1.25rem;margin-left:.5ex}
.quoteblock .attribution,.verseblock .attribution{font-size:.9375em;line-height:1.45;font-style:italic}
.quoteblock .attribution br,.verseblock .attribution br{display:none}
.quoteblock .attribution cite,.verseblock .attribution cite{display:block;letter-spacing:-.025em;color:rgba(0,0,0,.6)}
.quoteblock.abstract blockquote::before,.quoteblock.excerpt blockquote::before,.quoteblock .quoteblock blockquote::before{display:none}
.quoteblock.abstract blockquote,.quoteblock.abstract p,.quoteblock.excerpt blockquote,.quoteblock.excerpt p,.quoteblock .quoteblock blockquote,.quoteblock .quoteblock p{line-height:1.6;word-spacing:0}
.quoteblock.abstract{margin:0 1em 1.25em;display:block}
.quoteblock.abstract>.title{margin:0 0 .375em;font-size:1.15em;text-align:center}
.quoteblock.excerpt>blockquote,.quoteblock .quoteblock{padding:0 0 .25em 1em;border-left:.25em solid #dddddf}
.quoteblock.excerpt,.quoteblock .quoteblock{margin-left:0}
.quoteblock.excerpt blockquote,.quoteblock.excerpt p,.quoteblock .quoteblock blockquote,.quoteblock .quoteblock p{color:inherit;font-size:1.0625rem}
.quoteblock.excerpt .attribution,.quoteblock .quoteblock .attribution{color:inherit;font-size:.85rem;text-align:left;margin-right:0}
p.tableblock:last-child{margin-bottom:0}
td.tableblock>.content{margin-bottom:1.25em;word-wrap:anywhere}
td.tableblock>.content>:last-child{margin-bottom:-1.25em}
table.tableblock,th.tableblock,td.tableblock{border:0 solid #dedede}
table.grid-all>*>tr>*{border-width:1px}
table.grid-cols>*>tr>*{border-width:0 1px}
table.grid-rows>*>tr>*{border-width:1px 0}
table.frame-all{border-width:1px}
table.frame-ends{border-width:1px 0}
table.frame-sides{border-width:0 1px}
table.frame-none>colgroup+*>:first-child>*,table.frame-sides>colgroup+*>:first-child>*{border-top-width:0}
table.frame-none>:last-child>:last-child>*,table.frame-sides>:last-child>:last-child>*{border-bottom-width:0}
table.frame-none>*>tr>:first-child,table.frame-ends>*>tr>:first-child{border-left-width:0}
table.frame-none>*>tr>:last-child,table.frame-ends>*>tr>:last-child{border-right-width:0}
table.stripes-all>*>tr,table.stripes-odd>*>tr:nth-of-type(odd),table.stripes-even>*>tr:nth-of-type(even),table.stripes-hover>*>tr:hover{background:#f8f8f7}
th.halign-left,td.halign-left{text-align:left}
th.halign-right,td.halign-right{text-align:right}
th.halign-center,td.halign-center{text-align:center}
th.valign-top,td.valign-top{vertical-align:top}
th.valign-bottom,td.valign-bottom{vertical-align:bottom}
th.valign-middle,td.valign-middle{vertical-align:middle}
table thead th,table tfoot th{font-weight:bold}
tbody tr th{background:#f7f8f7}
tbody tr th,tbody tr th p,tfoot tr th,tfoot tr th p{color:rgba(0,0,0,.8);font-weight:bold}
p.tableblock>code:only-child{background:none;padding:0}
p.tableblock{font-size:1em}
ol{margin-left:1.75em}
ul li ol{margin-left:1.5em}
dl dd{margin-left:1.125em}
dl dd:last-child,dl dd:last-child>:last-child{margin-bottom:0}
li p,ul dd,ol dd,.olist .olist,.ulist .ulist,.ulist .olist,.olist .ulist{margin-bottom:.625em}
ul.checklist,ul.none,ol.none,ul.no-bullet,ol.no-bullet,ol.unnumbered,ul.unstyled,ol.unstyled{list-style-type:none}
ul.no-bullet,ol.no-bullet,ol.unnumbered{margin-left:.625em}
ul.unstyled,ol.unstyled{margin-left:0}
li>p:empty:only-child::before{content:"";display:inline-block}
ul.checklist>li>p:first-child{margin-left:-1em}
ul.checklist>li>p:first-child>.fa-square-o:first-child,ul.checklist>li>p:first-child>.fa-check-square-o:first-child{width:1.25em;font-size:.8em;position:relative;bottom:.125em}
ul.checklist>li>p:first-child>input[type=checkbox]:first-child{margin-right:.25em}
ul.inline{display:flex;flex-flow:row wrap;list-style:none;margin:0 0 .625em -1.25em}
ul.inline>li{margin-left:1.25em}
.unstyled dl dt{font-weight:400;font-style:normal}
ol.arabic{list-style-type:decimal}
ol.decimal{list-style-type:decimal-leading-zero}
ol.loweralpha{list-style-type:lower-alpha}
ol.upperalpha{list-style-type:upper-alpha}
ol.lowerroman{list-style-type:lower-roman}
ol.upperroman{list-style-type:upper-roman}
ol.lowergreek{list-style-type:lower-greek}
.hdlist>table,.colist>table{border:0;background:none}
.hdlist>table>tbody>tr,.colist>table>tbody>tr{background:none}
td.hdlist1,td.hdlist2{vertical-align:top;padding:0 .625em}
td.hdlist1{font-weight:bold;padding-bottom:1.25em}
td.hdlist2{word-wrap:anywhere}
.literalblock+.colist,.listingblock+.colist{margin-top:-.5em}
.colist td:not([class]):first-child{padding:.4em .75em 0;line-height:1;vertical-align:top}
.colist td:not([class]):first-child img{max-width:none}
.colist td:not([class]):last-child{padding:.25em 0}
.thumb,.th{line-height:0;display:inline-block;border:4px solid #fff;box-shadow:0 0 0 1px #ddd}
.imageblock.left{margin:.25em .625em 1.25em 0}
.imageblock.right{margin:.25em 0 1.25em .625em}
.imageblock>.title{margin-bottom:0}
.imageblock.thumb,.imageblock.th{border-width:6px}
.imageblock.thumb>.title,.imageblock.th>.title{padding:0 .125em}
.image.left,.image.right{margin-top:.25em;margin-bottom:.25em;display:inline-block;line-height:0}
.image.left{margin-right:.625em}
.image.right{margin-left:.625em}
a.image{text-decoration:none;display:inline-block}
a.image object{pointer-events:none}
sup.footnote,sup.footnoteref{font-size:.875em;position:static;vertical-align:super}
sup.footnote a,sup.footnoteref a{text-decoration:none}
sup.footnote a:active,sup.footnoteref a:active{text-decoration:underline}
#footnotes{padding-top:.75em;padding-bottom:.75em;margin-bottom:.625em}
#footnotes hr{width:20%;min-width:6.25em;margin:-.25em 0 .75em;border-width:1px 0 0}
#footnotes .footnote{padding:0 .375em 0 .225em;line-height:1.3334;font-size:.875em;margin-left:1.2em;margin-bottom:.2em}
#footnotes .footnote a:first-of-type{font-weight:bold;text-decoration:none;margin-left:-1.05em}
#footnotes .footnote:last-of-type{margin-bottom:0}
#content #footnotes{margin-top:-.625em;margin-bottom:0;padding:.75em 0}
div.unbreakable{page-break-inside:avoid}
.big{font-size:larger}
.small{font-size:smaller}
.underline{text-decoration:underline}
.overline{text-decoration:overline}
.line-through{text-decoration:line-through}
.aqua{color:#00bfbf}
.aqua-background{background:#00fafa}
.black{color:#000}
.black-background{background:#000}
.blue{color:#0000bf}
.blue-background{background:#0000fa}
.fuchsia{color:#bf00bf}
.fuchsia-background{background:#fa00fa}
.gray{color:#606060}
.gray-background{background:#7d7d7d}
.green{color:#006000}
.green-background{background:#007d00}
.lime{color:#00bf00}
.lime-background{background:#00fa00}
.maroon{color:#600000}
.maroon-background{background:#7d0000}
.navy{color:#000060}
.navy-background{background:#00007d}
.olive{color:#606000}
.olive-background{background:#7d7d00}
.purple{color:#600060}
.purple-background{background:#7d007d}
.red{color:#bf0000}
.red-background{background:#fa0000}
.silver{color:#909090}
.silver-background{background:#bcbcbc}
.teal{color:#006060}
.teal-background{background:#007d7d}
.white{color:#bfbfbf}
.white-background{background:#fafafa}
.yellow{color:#bfbf00}
.yellow-background{background:#fafa00}
span.icon>.fa{cursor:default}
a span.icon>.fa{cursor:inherit}
.admonitionblock td.icon [class^="fa icon-"]{font-size:2.5em;text-shadow:1px 1px 2px rgba(0,0,0,.5);cursor:default}
.admonitionblock td.icon .icon-note::before{content:"\f05a";color:#19407c}
.admonitionblock td.icon .icon-tip::before{content:"\f0eb";text-shadow:1px 1px 2px rgba(155,155,0,.8);color:#111}
.admonitionblock td.icon .icon-warning::before{content:"\f071";color:#bf6900}
.admonitionblock td.icon .icon-caution::before{content:"\f06d";color:#bf3400}
.admonitionblock td.icon .icon-important::before{content:"\f06a";color:#bf0000}
.conum[data-value]{display:inline-block;color:#fff!important;background:rgba(0,0,0,.8);border-radius:50%;text-align:center;font-size:.75em;width:1.67em;height:1.67em;line-height:1.67em;font-family:"Open Sans","DejaVu Sans",sans-serif;font-style:normal;font-weight:bold}
.conum[data-value] *{color:#fff!important}
.conum[data-value]+b{display:none}
.conum[data-value]::after{content:attr(data-value)}
pre .conum[data-value]{position:relative;top:-.125em}
b.conum *{color:inherit!important}
.conum:not([data-value]):empty{display:none}
dt,th.tableblock,td.content,div.footnote{text-rendering:optimizeLegibility}
h1,h2,p,td.content,span.alt,summary{letter-spacing:-.01em}
p strong,td.content strong,div.footnote strong{letter-spacing:-.005em}
p,blockquote,dt,td.content,td.hdlist1,span.alt,summary{font-size:1.0625rem}
p{margin-bottom:1.25rem}
.sidebarblock p,.sidebarblock dt,.sidebarblock td.content,p.tableblock{font-size:1em}
.exampleblock>.content{background:#fffef7;border-color:#e0e0dc;box-shadow:0 1px 4px #e0e0dc}
.print-only{display:none!important}
@page{margin:1.25cm .75cm}
@media print{*{box-shadow:none!important;text-shadow:none!important}
html{font-size:80%}
a{color:inherit!important;text-decoration:underline!important}
a.bare,a[href^="#"],a[href^="mailto:"]{text-decoration:none!important}
a[href^="http:"]:not(.bare)::after,a[href^="https:"]:not(.bare)::after{content:"(" attr(href) ")";display:inline-block;font-size:.875em;padding-left:.25em}
abbr[title]{border-bottom:1px dotted}
abbr[title]::after{content:" (" attr(title) ")"}
pre,blockquote,tr,img,object,svg{page-break-inside:avoid}
thead{display:table-header-group}
svg{max-width:100%}
p,blockquote,dt,td.content{font-size:1em;orphans:3;widows:3}
h2,h3,#toctitle,.sidebarblock>.content>.title{page-break-after:avoid}
#header,#content,#footnotes,#footer{max-width:none}
#toc,.sidebarblock,.exampleblock>.content{background:none!important}
#toc{border-bottom:1px solid #dddddf!important;padding-bottom:0!important}
body.book #header{text-align:center}
body.book #header>h1:first-child{border:0!important;margin:2.5em 0 1em}
body.book #header .details{border:0!important;display:block;padding:0!important}
body.book #header .details span:first-child{margin-left:0!important}
body.book #header .details br{display:block}
body.book #header .details br+span::before{content:none!important}
body.book #toc{border:0!important;text-align:left!important;padding:0!important;margin:0!important}
body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-break-before:always}
.listingblock code[data-lang]::before{display:block}
#footer{padding:0 .9375em}
.hide-on-print{display:none!important}
.print-only{display:block!important}
.hide-for-print{display:none!important}
.show-for-print{display:inherit!important}}
@media amzn-kf8,print{#header>h1:first-child{margin-top:1.25rem}
.sect1{padding:0!important}
.sect1+.sect1{border:0}
#footer{background:none}
#footer-text{color:rgba(0,0,0,.6);font-size:.9em}}
@media amzn-kf8{#header,#content,#footnotes,#footer{padding:0}}
</style>
<style>
pre.pygments .hll { background-color: #ffffcc }
pre.pygments { background: #f8f8f8; }
pre.pygments .tok-c { color: #3D7B7B; font-style: italic } /* Comment */
pre.pygments .tok-err { border: 1px solid #FF0000 } /* Error */
pre.pygments .tok-k { color: #008000; font-weight: bold } /* Keyword */
pre.pygments .tok-o { color: #666666 } /* Operator */
pre.pygments .tok-ch { color: #3D7B7B; font-style: italic } /* Comment.Hashbang */
pre.pygments .tok-cm { color: #3D7B7B; font-style: italic } /* Comment.Multiline */
pre.pygments .tok-cp { color: #9C6500 } /* Comment.Preproc */
pre.pygments .tok-cpf { color: #3D7B7B; font-style: italic } /* Comment.PreprocFile */
pre.pygments .tok-c1 { color: #3D7B7B; font-style: italic } /* Comment.Single */
pre.pygments .tok-cs { color: #3D7B7B; font-style: italic } /* Comment.Special */
pre.pygments .tok-gd { color: #A00000 } /* Generic.Deleted */
pre.pygments .tok-ge { font-style: italic } /* Generic.Emph */
pre.pygments .tok-gr { color: #E40000 } /* Generic.Error */
pre.pygments .tok-gh { color: #000080; font-weight: bold } /* Generic.Heading */
pre.pygments .tok-gi { color: #008400 } /* Generic.Inserted */
pre.pygments .tok-go { color: #717171 } /* Generic.Output */
pre.pygments .tok-gp { color: #000080; font-weight: bold } /* Generic.Prompt */
pre.pygments .tok-gs { font-weight: bold } /* Generic.Strong */
pre.pygments .tok-gu { color: #800080; font-weight: bold } /* Generic.Subheading */
pre.pygments .tok-gt { color: #0044DD } /* Generic.Traceback */
pre.pygments .tok-kc { color: #008000; font-weight: bold } /* Keyword.Constant */
pre.pygments .tok-kd { color: #008000; font-weight: bold } /* Keyword.Declaration */
pre.pygments .tok-kn { color: #008000; font-weight: bold } /* Keyword.Namespace */
pre.pygments .tok-kp { color: #008000 } /* Keyword.Pseudo */
pre.pygments .tok-kr { color: #008000; font-weight: bold } /* Keyword.Reserved */
pre.pygments .tok-kt { color: #B00040 } /* Keyword.Type */
pre.pygments .tok-m { color: #666666 } /* Literal.Number */
pre.pygments .tok-s { color: #BA2121 } /* Literal.String */
pre.pygments .tok-na { color: #687822 } /* Name.Attribute */
pre.pygments .tok-nb { color: #008000 } /* Name.Builtin */
pre.pygments .tok-nc { color: #0000FF; font-weight: bold } /* Name.Class */
pre.pygments .tok-no { color: #880000 } /* Name.Constant */
pre.pygments .tok-nd { color: #AA22FF } /* Name.Decorator */
pre.pygments .tok-ni { color: #717171; font-weight: bold } /* Name.Entity */
pre.pygments .tok-ne { color: #CB3F38; font-weight: bold } /* Name.Exception */
pre.pygments .tok-nf { color: #0000FF } /* Name.Function */
pre.pygments .tok-nl { color: #767600 } /* Name.Label */
pre.pygments .tok-nn { color: #0000FF; font-weight: bold } /* Name.Namespace */
pre.pygments .tok-nt { color: #008000; font-weight: bold } /* Name.Tag */
pre.pygments .tok-nv { color: #19177C } /* Name.Variable */
pre.pygments .tok-ow { color: #AA22FF; font-weight: bold } /* Operator.Word */
pre.pygments .tok-w { color: #bbbbbb } /* Text.Whitespace */
pre.pygments .tok-mb { color: #666666 } /* Literal.Number.Bin */
pre.pygments .tok-mf { color: #666666 } /* Literal.Number.Float */
pre.pygments .tok-mh { color: #666666 } /* Literal.Number.Hex */
pre.pygments .tok-mi { color: #666666 } /* Literal.Number.Integer */
pre.pygments .tok-mo { color: #666666 } /* Literal.Number.Oct */
pre.pygments .tok-sa { color: #BA2121 } /* Literal.String.Affix */
pre.pygments .tok-sb { color: #BA2121 } /* Literal.String.Backtick */
pre.pygments .tok-sc { color: #BA2121 } /* Literal.String.Char */
pre.pygments .tok-dl { color: #BA2121 } /* Literal.String.Delimiter */
pre.pygments .tok-sd { color: #BA2121; font-style: italic } /* Literal.String.Doc */
pre.pygments .tok-s2 { color: #BA2121 } /* Literal.String.Double */
pre.pygments .tok-se { color: #AA5D1F; font-weight: bold } /* Literal.String.Escape */
pre.pygments .tok-sh { color: #BA2121 } /* Literal.String.Heredoc */
pre.pygments .tok-si { color: #A45A77; font-weight: bold } /* Literal.String.Interpol */
pre.pygments .tok-sx { color: #008000 } /* Literal.String.Other */
pre.pygments .tok-sr { color: #A45A77 } /* Literal.String.Regex */
pre.pygments .tok-s1 { color: #BA2121 } /* Literal.String.Single */
pre.pygments .tok-ss { color: #19177C } /* Literal.String.Symbol */
pre.pygments .tok-bp { color: #008000 } /* Name.Builtin.Pseudo */
pre.pygments .tok-fm { color: #0000FF } /* Name.Function.Magic */
pre.pygments .tok-vc { color: #19177C } /* Name.Variable.Class */
pre.pygments .tok-vg { color: #19177C } /* Name.Variable.Global */
pre.pygments .tok-vi { color: #19177C } /* Name.Variable.Instance */
pre.pygments .tok-vm { color: #19177C } /* Name.Variable.Magic */
pre.pygments .tok-il { color: #666666 } /* Literal.Number.Integer.Long */
</style>
</head>
<body class="book">
<div id="header">
<h1>RISC-V Assembly Programmming</h1>
<div class="details">
<span id="author" class="author">Robert Winkler</span><br>
<span id="email" class="email"><a href="mailto:[email protected]">[email protected]</a></span><br>
<span id="revnumber">version 1.0.3,</span>
<span id="revdate">2024-11-30</span>
</div>
<div id="toc" class="toc">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#_info">Info</a></li>
<li><a href="#_dedication">Dedication</a></li>
<li><a href="#_chapter_0_hello_world">Chapter 0: Hello World</a>
<ul class="sectlevel2">
<li><a href="#_prereqs">Prereqs</a></li>
<li><a href="#_system_setup">System Setup</a></li>
<li><a href="#_handy_resources">Handy Resources</a></li>
<li><a href="#_hello_world">Hello World</a></li>
<li><a href="#_building_and_running">Building and Running</a></li>
<li><a href="#_conclusion">Conclusion</a></li>
<li><a href="#_exercises">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_1_data">Chapter 1: Data</a>
<ul class="sectlevel2">
<li><a href="#_arrays">Arrays</a></li>
<li><a href="#_exercises_2">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_2_environment_calls">Chapter 2: Environment Calls</a>
<ul class="sectlevel2">
<li><a href="#_examples">Examples</a></li>
<li><a href="#_exercises_3">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_3_branches_and_logic">Chapter 3: Branches and Logic</a>
<ul class="sectlevel2">
<li><a href="#_practice">Practice</a></li>
<li><a href="#_conclusion_2">Conclusion</a></li>
<li><a href="#_exercises_4">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_4_loops">Chapter 4: Loops</a>
<ul class="sectlevel2">
<li><a href="#_looping_through_arrays">Looping Through Arrays</a></li>
<li><a href="#_conclusion_3">Conclusion</a></li>
<li><a href="#_exercises_5">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_5_functions_and_the_risc_v_calling_convention">Chapter 5: Functions and the RISC-V Calling Convention</a>
<ul class="sectlevel2">
<li><a href="#_functions">Functions</a></li>
<li><a href="#_the_convention">The Convention</a></li>
<li><a href="#_conclusion_4">Conclusion</a></li>
<li><a href="#_exercises_6">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_6_floating_point_types">Chapter 6: Floating Point Types</a>
<ul class="sectlevel2">
<li><a href="#_floating_point_registers_and_instructions">Floating Point Registers and Instructions</a></li>
<li><a href="#_practice_2">Practice</a></li>
<li><a href="#_getting_floating_point_literals">Getting Floating Point Literals</a></li>
<li><a href="#_branching">Branching</a></li>
<li><a href="#_functions_2">Functions</a></li>
<li><a href="#_conclusion_5">Conclusion</a></li>
<li><a href="#_exercises_7">Exercises</a></li>
</ul>
</li>
<li><a href="#_chapter_7_tips_and_tricks">Chapter 7: Tips and Tricks</a>
<ul class="sectlevel2">
<li><a href="#_formatting">Formatting</a></li>
<li><a href="#_misc_general_tips">Misc. General Tips</a></li>
<li><a href="#_constants">Constants</a></li>
<li><a href="#_macros">Macros</a></li>
<li><a href="#_switch_case_statements">Switch-Case Statements</a></li>
<li><a href="#_command_line_arguments">Command Line Arguments</a></li>
<li><a href="#_no_pseudoinstructions_allowed">No Pseudoinstructions Allowed</a></li>
<li><a href="#_exercises_8">Exercises</a></li>
</ul>
</li>
<li><a href="#_appendix_a_venus">Appendix A: Venus</a>
<ul class="sectlevel2">
<li><a href="#_versions_and_history">Versions and History</a></li>
<li><a href="#_data_section">Data section</a></li>
<li><a href="#_environment_calls">Environment Calls</a></li>
<li><a href="#_constants_2">Constants</a></li>
<li><a href="#_conclusion_6">Conclusion</a></li>
</ul>
</li>
<li><a href="#_references_and_useful_links">References and Useful Links</a></li>
<li><a href="#_supporters">Supporters</a>
<ul class="sectlevel2">
<li><a href="#_corporate">Corporate</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_info">Info</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Copyright © 2021-2024 <a href="http://robertwinkler.com">Robert Winkler</a></p>
</div>
<div class="paragraph">
<p>This book is licensed under the <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/">Creative Commons BY-NC-SA 4.0</a>
which summarized means:</p>
</div>
<div class="paragraph">
<p>You are free to:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>Share</strong> — copy and redistribute the material in any medium or format</p>
</li>
<li>
<p><strong>Adapt</strong> — remix, transform, and build upon the material</p>
</li>
<li>
<p>The licensor cannot revoke these freedoms as long as you follow the license terms.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Under the following terms:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>Attribution</strong> — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.</p>
</li>
<li>
<p><strong>NonCommercial</strong> — You may not use the material for commercial purposes.</p>
</li>
<li>
<p><strong>ShareAlike</strong> — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.</p>
</li>
<li>
<p><strong>No additional restrictions</strong> — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>This book is available online in
<a href="https://www.robertwinkler.com/projects/riscv_book/riscv_book.html">HTML</a>,
<a href="https://www.robertwinkler.com/projects/riscv_book/riscv_book.pdf">PDF</a>, and
<a href="https://www.robertwinkler.com/projects/riscv_book/riscv_book.epub">EPUB</a> form.</p>
</div>
<div class="paragraph">
<p>You can support the book and purchase the chapter exercise solutions
from <a href="https://store.robertwinkler.com/">my store</a> or
<a href="https://leanpub.com/riscvassemblyprogrammming">Leanpub</a>.</p>
</div>
<div class="paragraph">
<p>The repo for the book, where you can get the code referenced and report
any errors (submit an issue or even a pull request) is
<a href="https://github.com/rswinkle/riscv_book">here</a>. The code is MIT licensed.</p>
</div>
<div class="paragraph">
<p>If you’re interested in contacting me regarding RISC-V tutoring or any other
business request related to the book, you can reach me at <a href="mailto:[email protected]">[email protected]</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_dedication">Dedication</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This book is dedicated to all its <a href="#_supporters">supporters</a> and all the students
I’ve helped with RISC-V over the years who inspired me to create it.</p>
</div>
<div class="paragraph">
<p>Thank you.</p>
</div>
<div class="paragraph">
<p>An extra thank you goes to the corporate level sponsors below:</p>
</div>
<table class="tableblock frame-none grid-none fit-content">
<colgroup>
<col>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><div class="content"><div class="imageblock">
<div class="content">
<a class="image" href="http://www.robertwinkler.com/projects/riscv_book/"><img src="images/riscv_book.png" alt="Cover Logo" width="250" height="250"></a>
</div>
</div></div></td>
<td class="tableblock halign-left valign-top"><div class="content"><div class="imageblock">
<div class="content">
<a class="image" href="http://www.robertwinkler.com/"><img src="images/gravatar_250.png" alt="My Gravatar" width="250" height="250"></a>
</div>
</div></div></td>
<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph">
<p> </p>
</div></div></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="sect1">
<h2 id="_chapter_0_hello_world">Chapter 0: Hello World</h2>
<div class="sectionbody">
<div class="paragraph">
<p>In which we lay the groundwork for the rest of the book…​</p>
</div>
<div class="sect2">
<h3 id="_prereqs">Prereqs</h3>
<div class="paragraph">
<p>While someone with no programming experience could probably learn RISC-V from this
book, it is definitely preferable to have at least some experience in a higher
level imperative programming language. I say imperative, because programming
in assembly is the antithesis of functional programming; everything is about
state, with each line changing the state of the CPU and sometimes memory. Given
that, experience in functional languages like Lisp, Scheme etc. are less helpful
than experience in C/C++, Java, Python, Javascript etc.</p>
</div>
<div class="paragraph">
<p>Of all of the latter, C is the best, with C++ being a close second because at least
all of C exists in C++. There are many reasons C is the best prior experience when
learning assembly (any assembly, not just RISC-V), including the following:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>pointers, concepts and symmetry of "address of" and "dereference" operators</p>
</li>
<li>
<p>pointer/array syntax equivalence</p>
</li>
<li>
<p>stack allocation as the default</p>
</li>
<li>
<p>manual memory management, no garbage collector</p>
</li>
<li>
<p>global data</p>
</li>
<li>
<p>rough equivalence in structure of a C program and an assembly program (vs. say Java)</p>
</li>
<li>
<p>pass by value</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>There is some overlap between those and there are probably more, but you can see that
most other languages that are commonly taught as first languages are missing most, if
not all of those things.</p>
</div>
<div class="paragraph">
<p>Even C++, which technically has all of them being a superset of C,
is usually taught in a way that mostly ignores all of those things. They teach
C++ as if it’s Java, never teaching the fundamentals. In any case this
is getting into my problems with CS pedagogy of the last 20 years based on my
experience as a CS major myself ('12) and as a programming tutor helping college
students across the country since 2016, and I should save it for a proper
essay/rant sometime.</p>
</div>
<div class="paragraph">
<p>Long story short, I use C code and C syntax to help explain and teach RISC-V. I’ll
try to provide enough explanation regardless of past experience as best I can.</p>
</div>
</div>
<div class="sect2">
<h3 id="_system_setup">System Setup</h3>
<div class="paragraph">
<p>As I tell all of my tutoring students, if you’re majoring in CS or anything related
I highly recommend you use Linux. It’s easier in every way to do dev work
on Linux vs Windows or Mac. Many assignments require it, which often necessitates
using a virtual machine (which is painful, especially on laptops) and/or ssh-ing
into a school Linux server, which is also less than ideal. In general, you’ll have
to learn how to use the Unix terminal eventually and will probably use it to some
extent in your career so it also makes sense to get used to it asap.</p>
</div>
<div class="paragraph">
<p>That being said, Windows does now have WSL so you can get the full Ubuntu or Debian
or Fedora etc. terminal based system on Windows without having to setup a real
virtual machine (or dealing with the slowdown that would cause). I’ve even heard
that they’ll get support for Linux GUI programs soon.</p>
</div>
<div class="paragraph">
<p>MacOS on the other hand, is technically a Unix based system and you can use their
terminal and install virtually any program from there using Macports or Homebrew
or similar.</p>
</div>
<div class="paragraph">
<p>There are a few RISC-V simulators that I know of and have used:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>RARS is a RISC-V port of MARS, a Java GUI based simulator with dozens of extra
environment calls, syntactic sugar and features like graphics, memory mapped I/O, etc.</p>
</li>
<li>
<p>Venus, a web based simulator used by Berkeley (also has a downloadable jar)</p>
</li>
<li>
<p>Ripes, a graphical processor simulator and assembly editor for bare bones assembly
programming</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Of those three, RARS is by far the most full featured and user friendly for learning
since it forked from the venerable MARS MIPS simulator. It is also the most
commonly used by students outside of Berkeley. Given that, this book will focus
primarily on RARS, though most of it applies equally well to Venus. <a href="#_appendix_a_venus">Appendix A: Venus</a>
covers the differences between RARS and Venus.</p>
</div>
<div class="paragraph">
<p>You can download/access both at the following links:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a href="https://github.com/TheThirdOne/rars">RARS</a></p>
</li>
<li>
<p><a href="https://github.com/rarsm/rars">RARSM</a> RARS iMproved; fork of RARS with fixes/features</p>
</li>
<li>
<p><a href="https://github.com/ThaumicMekanism/venus">ThaumicMekanism’s Venus</a>
Get the jar <a href="https://thaumicmekanism.github.io/venus/jvm/venus-jvm-latest.jar">here</a></p>
</li>
<li>
<p><a href="https://github.com/61c-teach/venus">CS 61C’s Venus</a>
Get the jar <a href="https://inst.eecs.berkeley.edu/~cs61c/fa22/tools/venus-latest.jar">here</a>.</p>
</li>
</ul>
</div>
</div>
<div class="sect2">
<h3 id="_handy_resources">Handy Resources</h3>
<div class="paragraph">
<p>There are a few references that you should bookmark (or download) before you get started.
The first is the
<a href="https://raw.githubusercontent.com/rswinkle/riscv_book/master/references/riscv_greensheet.pdf">RISC-V Greensheet</a>.
It’s possible you already have a physical copy of this as it’s actually the tearout from the Patterson
and Hennessey textbook <a href="https://amzn.to/3i6Rj9p"><em>Computer Architecture and Design</em></a>
that is commonly used in college courses. Berkeley provides a similar
<a href="https://raw.githubusercontent.com/rswinkle/riscv_book/master/references/reference-card.pdf">reference sheet</a>
with the same information.</p>
</div>
<div class="paragraph">
<p>There is also a large format of the
<a href="https://raw.githubusercontent.com/rswinkle/riscv_book/master/references/riscv_greensheet_large.pdf">greensheet</a>.</p>
</div>
<div class="paragraph">
<p>The second thing is the list of
<a href="https://github.com/TheThirdOne/rars/wiki/Environment-Calls">environment calls</a> (aka ecalls,
system calls, syscalls) from the RARS wiki.</p>
</div>
<div class="paragraph">
<p>I recommend you download/bookmark both and keep them open while working because
you’ll be referencing them often to remind yourself which instructions and ecalls
you have available and how they work.</p>
</div>
</div>
<div class="sect2">
<h3 id="_hello_world">Hello World</h3>
<div class="paragraph">
<p>Let’s start with the classic hello world program, first in C, then in RISC-V, and go
over all the pieces in overview. You can copy paste these into your editor of choice
(mine being neovim), or use the files in the associated repo to follow along.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c"><div class="lineno"><table class="linenotable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span>
<span class="normal">6</span>
<span class="normal">7</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-cp">#include</span><span class="tok-w"> </span><span class="tok-cpf"><stdio.h></span>
<span class="tok-kt">int</span><span class="tok-w"> </span><span class="tok-nf">main</span><span class="tok-p">()</span>
<span class="tok-p">{</span>
<span class="tok-w"> </span><span class="tok-n">printf</span><span class="tok-p">(</span><span class="tok-s">"Hello World!</span><span class="tok-se">\n</span><span class="tok-s">"</span><span class="tok-p">);</span>
<span class="tok-w"> </span><span class="tok-k">return</span><span class="tok-w"> </span><span class="tok-mi">0</span><span class="tok-p">;</span>
<span class="tok-p">}</span>
</pre></div></td></tr></table></div></code></pre>
</div>
</div>
<div class="paragraph">
<p>It is pretty self explanatory. You have to include stdio.h so you can use the
function printf (though in the real world I’d use puts here), the function main
is the start of any C/C++ program, which is a function that returns
an int. We call printf to display the string "Hello World!\n" to the user and
then return 0 to exit. Returning 0 indicates success and there were no errors.</p>
</div>
<div class="paragraph">
<p>You can compile and run it in a linux/unix terminal as shown below. You
can substitute clang or another compiler for gcc if you want.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="console"><span></span><span class="tok-gp">$ </span>gcc<span class="tok-w"> </span>-o<span class="tok-w"> </span>hello<span class="tok-w"> </span>hello.c
<span class="tok-gp">$ </span>./hello
<span class="tok-go">Hello World!</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>Now, the same program in RISC-V:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="riscv"><div class="lineno"><table class="linenotable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span></pre></div></td><td class="code"><div><pre><span></span>.data
hello: .asciz "Hello World!\n"
.text
main:
li a7, 4 # load immediate, a7 = 4 (4 is print string system call)
la a0, hello # load address of string to print into a0
ecall
li a7, 10 # exit ecall
ecall
</pre></div></td></tr></table></div></code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>.data</code> section is where you declare global variables, which includes string
literals as in this case. We’ll cover them in more detail later.</p>
</div>
<div class="paragraph">
<p>The <code>.text</code> section is where any code goes. Here we declare a single label <code>main:</code>,
indicating the start of our main function.</p>
</div>
<div class="paragraph">
<p>We then put the number 4 in the <code>a7</code> register to select the print string system
call. The print string system call takes one argument, the address of the string
to print, in the <code>a0</code> register. We do that on the next line. On line 8, we call
the system call using the ecall instruction.</p>
</div>
<div class="paragraph">
<p>Finally we call the exit system call which takes no arguments and exits the program.</p>
</div>
<div class="paragraph">
<p>Again, we’ll cover system calls in a later chapter. This is just an intro/overview
so don’t worry if some things aren’t completely clear. This chapter is about getting
you up and running, not really about teaching anything specific yet.</p>
</div>
</div>
<div class="sect2">
<h3 id="_building_and_running">Building and Running</h3>
<div class="paragraph">
<p>Now that we have our hello world RISC-V program, how do we run it? Well the easiest
and quickest<sup class="footnote">[<a id="_footnoteref_1" class="footnote" href="#_footnotedef_1" title="View footnote.">1</a>]</sup> way is of course to do it on the command line, which can be done like
this:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="console"><span></span><span class="tok-gp">$ </span>java<span class="tok-w"> </span>-jar<span class="tok-w"> </span>~/rars_latest.jar<span class="tok-w"> </span>hello.s
<span class="tok-go">RARS 1.5 Copyright 2003-2019 Pete Sanderson and Kenneth Vollmar</span>
<span class="tok-go">Hello World!</span>
<span class="tok-go">Program terminated by calling exit</span></code></pre>
</div>
</div>
<div class="paragraph">
<p>The name of your RARS jar file may be different<sup class="footnote">[<a id="_footnoteref_2" class="footnote" href="#_footnotedef_2" title="View footnote.">2</a>]</sup>, so be sure to
use the correct name and path. For myself, I keep the jar file in my home
directory so I can use tilde to access it no matter where I am. You can also
copy it into your working directory (ie wherever you have your source code) so you
don’t have to specify a path at all. There are lots of useful command line options
that you can use<sup class="footnote">[<a id="_footnoteref_3" class="footnote" href="#_footnotedef_3" title="View footnote.">3</a>]</sup>, some of which we’ll touch on later.</p>
</div>
<div class="paragraph">
<p>Running the jar directly on the command line works even in the Windows/DOS command
line though I’ve never done it and it’s probably not worth it.</p>
</div>