Code Generation/Exercise 11: Difference between revisions
From Wiki**3
< Code Generation
| Line 62: | Line 62: | ||
SUB | SUB | ||
I2D | I2D | ||
DDUP ; compute assignment value | |||
; compute &v[i] == v+i*sizeof(double) | ; compute &v[i] == v+i*sizeof(double) | ||
| Line 72: | Line 74: | ||
ADD ; &v[i] | ADD ; &v[i] | ||
DSTORE ; do double assignment | DSTORE ; do assignment of double value | ||
TRASH 8 ; discard assignment value | |||
; END assignment to v[i] | ; END assignment to v[i] | ||
| Line 106: | Line 110: | ||
LOAD | LOAD | ||
I2D | I2D | ||
DDUP ; compute assignment value | |||
; compute &v[i] == v+i*sizeof(double) | ; compute &v[i] == v+i*sizeof(double) | ||
| Line 116: | Line 122: | ||
ADD ; &v[i] | ADD ; &v[i] | ||
DSTORE ; do double assignment | DSTORE ; do assignment of double value | ||
TRASH 8 ; discard assignment value | |||
; END if block | ; END if block | ||
Revision as of 07:25, 9 May 2017
Problema
Considere o seguinte código C++ (assuma que ponteiros e int ocupam 32 bits e que double ocupa 64 bits).
<cpp> double *forall(double *v) {
const static int limit = 1024;
for (int i = 0; i < limit; i++) {
v[i] = 3 * i – sizeof(double);
if (v[i] > 2 * i) v[i] = limit;
}
return v;
} </cpp>
Código Postfix (não optimizado)
O código Postfix correspondente à função é o seguinte (agradece-se a comunicação de questões relativas a este código).
No código Postfix, BB# significa "bloco básico número".
<asm> TEXT ALIGN GLOBAL forall, FUNC LABEL forall ENTER 4 ; i@-4 v@+8
- define "limit" (this is not an assignment)
RODATA ALIGN LABEL limit CONST 1024
- done - go back to code segment
TEXT ALIGN
- initialize for-loop control variable (again, not an assignment)
INT 0 LOCAL -4 STORE ; i = 0
- for-loop test
LOCAL -4 LOAD ; i ADDR limit LOAD ; limit LT ; i<limit JZ forend
- BEGIN for-loop body
- BEGIN assignment to v[i]
- compute and promote 3*i-sizeof(double)
INT 3 LOCAL -4 ; &i LOAD ; i MUL INT 8 ; sizeof(double) SUB I2D
DDUP ; compute assignment value
- compute &v[i] == v+i*sizeof(double)
LOCAL +8 ; &v LOAD ; v LOCAL -4 ; &i LOAD ; i INT 8 ; sizeof(double) MUL ADD ; &v[i]
DSTORE ; do assignment of double value
TRASH 8 ; discard assignment value
- END assignment to v[i]
- if condition
- compute &v[i] == v+i*sizeof(double)
LOCAL +8 ; &v LOAD ; v LOCAL -4 ; &i LOAD ; i INT 8 ; sizeof(double) MUL ADD ; &v[i] DLOAD ; v[i]
- compute and promote 2*i
INT 2 LOCAL -4 ; &i LOAD ; i MUL I2D
- compare
DCMP INT 0 GT
- BEGIN if block
- do assignment (double)
- load and promote "limit"
ADDR limit LOAD I2D
DDUP ; compute assignment value
- compute &v[i] == v+i*sizeof(double)
LOCAL +8 ; &v LOAD ; v LOCAL -4 ; &i LOAD ; i INT 8 ; sizeof(double) MUL ADD ; &v[i]
DSTORE ; do assignment of double value
TRASH 8 ; discard assignment value
- END if block
- END for-loop body
- return *v
LOCAL +8 ; &v LOAD ; v POP LEAVE RET
</asm>
Compiling and Running
Para compilar o código Postfix directamente, pode ser utilizada a ferramenta pf2asm (assumindo uma arquitectura de 32 bits):
pf2asm forall.pf yasm -felf forall.asm