The code for the figure above has a CPWA at 000C to test the value of j. Because the program branches to that instruction from the bottom of the loop, why doesn’t the compiler generate an LDWA j, d at that point before the compare instruction?

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
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The code for the figure above has a CPWA at 000C to test the value of j. Because the program branches to that instruction from the bottom of the loop, why doesn’t the compiler generate an LDWA j, d at that point before the compare instruction?

High-Order Language
include «etdio.h>
int main() (
int ji
for (j 0: j 3; j {
printf ( sd\n". j):
return 0;
Assembly Language
0000 120003
ji
BR
nain
.EQUATE O
ilocal variable #2a
0003 580002 main:
SUDSP
2,1
ipush #j
0006 Co0000
ifor (- 0
LDWA
0,1
0009 E30000
STKA
1,8
000c ADD003 for:
3,1
i < 3
CPKA
000P 1C002A
BRGE
endPor
0012 49002E
STRO
neg.d
iprintt( sdin", j)
0015 3B000D
DECO
0018 DO00GA
LODA
001B FIFC16
001E C30000
STBA
charout,d
LOMA
0021 600001
ADDA
1,i
0024 E30000
STWA
1.8
0027 12000C
BR
for
002A 500002 endPor: ADDSP
2,1
pop
002D 00
STOP
0028 GA203D mag:
.ASCII j \x00
2000
0033
. END
Transcribed Image Text:High-Order Language include «etdio.h> int main() ( int ji for (j 0: j 3; j { printf ( sd\n". j): return 0; Assembly Language 0000 120003 ji BR nain .EQUATE O ilocal variable #2a 0003 580002 main: SUDSP 2,1 ipush #j 0006 Co0000 ifor (- 0 LDWA 0,1 0009 E30000 STKA 1,8 000c ADD003 for: 3,1 i < 3 CPKA 000P 1C002A BRGE endPor 0012 49002E STRO neg.d iprintt( sdin", j) 0015 3B000D DECO 0018 DO00GA LODA 001B FIFC16 001E C30000 STBA charout,d LOMA 0021 600001 ADDA 1,i 0024 E30000 STWA 1.8 0027 12000C BR for 002A 500002 endPor: ADDSP 2,1 pop 002D 00 STOP 0028 GA203D mag: .ASCII j \x00 2000 0033 . END
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