Difference between revisions of "Code Generation/Exercise 9"

Latest revision as of 17:51, 6 May 2019

The Original Code

Consider the following C code and assume that the size of pointers, int, and unsigned long is 32 bits and that the size of double is 64 bits.

static unsigned long a = 10;
static double *v;
extern void *malloc(unsigned long);

static double *mkvec(unsigned long n) {
  if (n < 1) return (double *)0;
  unsigned long s = sizeof(double);
  double *v = (double *)malloc(n * s);
  return v;
}

double *compute() {
  v = mkvec(a * 4);
  for (unsigned long i = 1; i < a; i++)
    if (v[i] > v[0]) v[i] = 3 * i - 1;
  return v;
}

Postfix Code

The Postfix code for the above code is as follows: (code has not been thoroughly checked: bug reports are welcome)

In the following code sections, BB# means "basic block number".

Static (global) variables
;; variable "a" DATA ALIGN LABEL a SINT 10 ;; variable "v" DATA ; "static" variables are always initialized ALIGN LABEL v SINT 0 ; this is a null pointer

Declaration of external function
EXTERN malloc

Function "mkvec"

;; start of BB1
TEXT
ALIGN
LABEL mkvec
ENTER 8  ; s@-4 v@-8
LOCAL 8
LDINT
INT 1
LT
JZ ifend1
;; end of BB1

;; start of BB2
INT 0
STFVAL32
LEAVE
RET
;; end of BB2

;; start of BB3
ALIGN
LABEL ifend1
INT 8  ; sizeof(double)
LOCAL -4
STINT
LOCAL +8
LDINT
LOCAL -4
LDINT
MUL
CALL malloc
;; end of BB3

;; start of BB4
TRASH 4
LDFVAL32
LOCAL -8
STINT
LOCAL -8
LDINT
STFVAL32
LEAVE
RET
;; end of BB4

Function "compute"

;; start of BB1
TEXT
ALIGN
GLOBAL compute, FUNC
LABEL compute
ENTER 4  ; i@-4
ADDR a
LDINT
INT 4
MUL
CALL mkvec
;; end of BB1

;; start of BB2
TRASH 4
LDFVAL32
DUP32
ADDR v
STINT
TRASH 4
INT 1
LOCAL -4
STINT
;; end of BB2

;; start of BB3
ALIGN
LABEL fortest
LOCAL -4
LDINT
ADDR a
LDINT
LT
JZ forend
;; end of BB3

;; start of BB4
ADDR v
LDINT
LOCAL -4
LDINT
INT 8
MUL
ADD
LDDOUBLE
ADDR v
LDINT
INT 0
INT 8
MUL
ADD
LDDOUBLE
DCMP
INT 0
GT
JZ ifend2
;; end of BB4

;; start of BB5
INT 3
LOCAL -4
LDINT
MUL
INT 1
SUB
I2D
DUP64
ADDR v
LDINT
LOCAL -4
LDINT
INT 8
MUL
ADD
STDOUBLE
TRASH 8
;; end of BB5

;; start of BB6
ALIGN
LABEL ifend2
ALIGN
LABEL forincr
LOCAL -4
LDINT
DUP32
INT 1
ADD
LOCAL -4
STINT
TRASH 4
JMP fortest
;; end of BB6

;; start of BB7
ALIGN
LABEL forend
ADDR v
LDINT
STFVAL32
LEAVE
RET
;; end of BB7

Compiling and Running

To compile the Postfix code directly, pf2asm can be used (assuming a 32-bit architecture):

pf2asm compute.pf
yasm -felf compute.asm

Difference between revisions of "Code Generation/Exercise 9"

From Wiki**3

< Code Generation

Latest revision as of 17:51, 6 May 2019

Contents

The Original Code

Postfix Code

Compiling and Running

@@ Line 4: / Line 4: @@
 Consider the following C code and assume that the size of pointers, '''int''', and '''unsigned long''' is 32 bits and that the size of '''double''' is 64 bits.
-<c>
+<source lang="c">
 static unsigned long a = 10;
 static double *v;
@@ Line 22: / Line 22: @@
    return v;
 }
-</c>
+</source>
 == Postfix Code ==
@@ Line 30: / Line 30: @@
 In the following code sections, '''BB#''' means "[[Optimization Topics|basic block]] number".
-{{CollapsedCode|Variables|
+{{CollapsedCode|Static (global) variables|
-<asm>
+<source lang="asm">
 ;; variable "a"
 DATA
 ALIGN
 LABEL a
-CONST 10
+SINT 10
 ;; variable "v"
@@ Line 42: / Line 42: @@
 ALIGN
 LABEL v
-CONST 0  ; this is a null pointer
+SINT 0  ; this is a null pointer
-</asm>
+</source>
 }}
-=== Declaration of external function ===
+{{CollapsedCode|Declaration of external function|
-<asm>
+<source lang="asm">
 EXTERN malloc
-</asm>
+</source>
+}}
-=== Function "mkvec" ===
+{{CollapsedCode|Function "mkvec"|
+<source lang="asm">
-<asm>
 ;; start of BB1
 TEXT
@@ Line 60: / Line 60: @@
 ENTER 8  ; s@-4 v@-8
 LOCAL 8
-LOAD
+LDINT
 INT 1
 LT
@@ Line 68: / Line 68: @@
 ;; start of BB2
 INT 0
-POP
+STFVAL32
 LEAVE
 RET
@@ Line 78: / Line 78: @@
 INT 8  ; sizeof(double)
 LOCAL -4
-STORE
+STINT
 LOCAL +8
-LOAD
+LDINT
 LOCAL -4
-LOAD
+LDINT
 MUL
 CALL malloc
@@ Line 89: / Line 89: @@
 ;; start of BB4
 TRASH 4
-PUSH
+LDFVAL32
 LOCAL -8
-STORE
+STINT
 LOCAL -8
-LOAD
+LDINT
-POP
+STFVAL32
 LEAVE
 RET
 ;; end of BB4
-</asm>
+</source>
+}}
-=== Function "compute" ===
+{{CollapsedCode|Function "compute"|
+<source lang="asm">
-<asm>
 ;; start of BB1
 TEXT
@@ Line 110: / Line 110: @@
 ENTER 4  ; i@-4
 ADDR a
-LOAD
+LDINT
 INT 4
 MUL
@@ Line 118: / Line 118: @@
 ;; start of BB2
 TRASH 4
-PUSH
+LDFVAL32
-DUP
+DUP32
 ADDR v
-STORE
+STINT
 TRASH 4
 INT 1
 LOCAL -4
-STORE
+STINT
 ;; end of BB2
@@ Line 132: / Line 132: @@
 LABEL fortest
 LOCAL -4
-LOAD
+LDINT
 ADDR a
-LOAD
+LDINT
 LT
 JZ forend
@@ Line 141: / Line 141: @@
 ;; start of BB4
 ADDR v
-LOAD
+LDINT
 LOCAL -4
-LOAD
+LDINT
 INT 8
 MUL
 ADD
-DLOAD
+LDDOUBLE
 ADDR v
-LOAD
+LDINT
 INT 0
 INT 8
 MUL
 ADD
-DLOAD
+LDDOUBLE
 DCMP
 INT 0
@@ Line 164: / Line 164: @@
 INT 3
 LOCAL -4
-LOAD
+LDINT
 MUL
 INT 1
 SUB
 I2D
-DDUP
+DUP64
 ADDR v
-LOAD
+LDINT
 LOCAL -4
-LOAD
+LDINT
 INT 8
 MUL
 ADD
-DSTORE
+STDOUBLE
 TRASH 8
 ;; end of BB5
@@ Line 187: / Line 187: @@
 LABEL forincr
 LOCAL -4
-LOAD
+LDINT
-DUP
+DUP32
 INT 1
 ADD
 LOCAL -4
-STORE
+STINT
 TRASH 4
 JMP fortest
@@ Line 201: / Line 201: @@
 LABEL forend
 ADDR v
-LOAD
+LDINT
-POP
+STFVAL32
 LEAVE
 RET
 ;; end of BB7
-</asm>
+</source>
+}}
 == Compiling and Running ==
-To compile the Postfix code directly, [[pf2asm]] can be used (assuming a 32-bit architecture):
+To compile the Postfix code directly, [[Compiladores/Projecto de Compiladores/Compiladores Exemplo|pf2asm]] can be used (assuming a 32-bit architecture):
   pf2asm compute.pf