Github user mengxr commented on the pull request:
https://github.com/apache/spark/pull/6137#issuecomment-101916289
Thanks for the discussion! I checked the bytecode and confirmed that there
are extra calls. This is the test Scala code:
~~~scala
class A {
val b = Array(1.0, 2.0)
private[this] val c = Array(1.0, 2.0)
def f1() {
val a = Array(1.0, 2.0)
var i = 0
while (i < a.length) {
a(i) += 1
i += 1
}
}
def f2() {
val a = Array(1.0, 2.0)
var i = 0
val n = a.length
while (i < n) {
a(i) += 1
i += 1
}
}
def f3() {
var i = 0
while (i < b.length) {
b(i) += 1
i + 1
}
}
def f4() {
val localB = b
var i = 0
while (i < localB.length) {
localB(i) += 1
i + 1
}
}
def f5() {
var i = 0
while (i < c.length) {
c(i) += 1
i += 1
}
}
def f6() {
var i = 0
val n = c.length
while (i < n) {
c(i) += 1
i += 1
}
}
def f7() {
val localC = c
var i = 0
val n = localC.length
while (i < n) {
localC(i) += 1
i += 1
}
}
}
~~~
and this is the bytecode
~~~
public void f1();
Code:
0: iconst_2
1: newarray double
3: dup
4: iconst_0
5: dconst_1
6: dastore
7: dup
8: iconst_1
9: ldc2_w #19 // double 2.0d
12: dastore
13: astore_1
14: iconst_0
15: istore_2
16: iload_2
17: aload_1
18: arraylength
19: if_icmpge 40
22: iload_2
23: istore_3
24: aload_1
25: iload_3
26: aload_1
27: iload_3
28: daload
29: iconst_1
30: i2d
31: dadd
32: dastore
33: iload_2
34: iconst_1
35: iadd
36: istore_2
37: goto 16
40: return
public void f2();
Code:
0: iconst_2
1: newarray double
3: dup
4: iconst_0
5: dconst_1
6: dastore
7: dup
8: iconst_1
9: ldc2_w #19 // double 2.0d
12: dastore
13: astore_1
14: iconst_0
15: istore_2
16: aload_1
17: arraylength
18: istore_3
19: iload_2
20: iload_3
21: if_icmpge 45
24: iload_2
25: istore 4
27: aload_1
28: iload 4
30: aload_1
31: iload 4
33: daload
34: iconst_1
35: i2d
36: dadd
37: dastore
38: iload_2
39: iconst_1
40: iadd
41: istore_2
42: goto 19
45: return
public void f3();
Code:
0: iconst_0
1: istore_1
2: iload_1
3: aload_0
4: invokevirtual #29 // Method b:()[D
7: arraylength
8: if_icmpge 35
11: iload_1
12: istore_2
13: aload_0
14: invokevirtual #29 // Method b:()[D
17: iload_2
18: aload_0
19: invokevirtual #29 // Method b:()[D
22: iload_2
23: daload
24: iconst_1
25: i2d
26: dadd
27: dastore
28: iload_1
29: iconst_1
30: iadd
31: pop
32: goto 2
35: return
public void f4();
Code:
0: aload_0
1: invokevirtual #29 // Method b:()[D
4: astore_1
5: iconst_0
6: istore_2
7: iload_2
8: aload_1
9: arraylength
10: if_icmpge 31
13: iload_2
14: istore_3
15: aload_1
16: iload_3
17: aload_1
18: iload_3
19: daload
20: iconst_1
21: i2d
22: dadd
23: dastore
24: iload_2
25: iconst_1
26: iadd
27: pop
28: goto 7
31: return
public void f5();
Code:
0: iconst_0
1: istore_1
2: iload_1
3: aload_0
4: getfield #34 // Field c:[D
7: arraylength
8: if_icmpge 35
11: iload_1
12: istore_2
13: aload_0
14: getfield #34 // Field c:[D
17: iload_2
18: aload_0
19: getfield #34 // Field c:[D
22: iload_2
23: daload
24: iconst_1
25: i2d
26: dadd
27: dastore
28: iload_1
29: iconst_1
30: iadd
31: istore_1
32: goto 2
35: return
public void f6();
Code:
0: iconst_0
1: istore_1
2: aload_0
3: getfield #34 // Field c:[D
6: arraylength
7: istore_2
8: iload_1
9: iload_2
10: if_icmpge 37
13: iload_1
14: istore_3
15: aload_0
16: getfield #34 // Field c:[D
19: iload_3
20: aload_0
21: getfield #34 // Field c:[D
24: iload_3
25: daload
26: iconst_1
27: i2d
28: dadd
29: dastore
30: iload_1
31: iconst_1
32: iadd
33: istore_1
34: goto 8
37: return
public void f7();
Code:
0: aload_0
1: getfield #34 // Field c:[D
4: astore_1
5: iconst_0
6: istore_2
7: aload_1
8: arraylength
9: istore_3
10: iload_2
11: iload_3
12: if_icmpge 36
15: iload_2
16: istore 4
18: aload_1
19: iload 4
21: aload_1
22: iload 4
24: daload
25: iconst_1
26: i2d
27: dadd
28: dastore
29: iload_2
30: iconst_1
31: iadd
32: istore_2
33: goto 10
36: return
~~~
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