Intel Itanium 9150M, Manual, Page: 58 / 420

Volume 3: Instruction Reference 3:49
czx
czx — Compute Zero Index
Format: (
qp
) czx1.l
r
1
=
r
3
one_byte_form, left_form I29
(
qp
) czx1.r
r
1
=
r
3
one_byte_form, right_form I29
(
qp
) czx2.l
r
1
=
r
3
two_byte_form, left_form I29
(
qp
) czx2.r
r
1
=
r
3
two_byte_form, right_form I29
Description:
GR
r
3
is scanned for a zero element. The element is either an 8-bit aligned byte
(one_byte_form) or a 16-bit aligned pair of bytes (two_byte_form). The index of the
first zero element is placed in GR
r
1
. If there are no zero elements in GR
r
3
, a default
value is placed in GR
r
1
. Table 2-21 gives the possible result values. In the left_form,
the source is scanned from most significant element to least significant element, and in
the right_form it is scanned from least significant element to most significant element.
Operation: if (PR[ qp ]) {
check_target_register( r
1
);
if (one_byte_form) {
if (left_form) { // scan from most significant down
if ((GR[ r
3
] & 0xff00000000000000) == 0) GR[ r
1
] = 0;
else if ((GR[ r
3
] & 0x00ff000000000000) == 0) GR[ r
1
] = 1;
else if ((GR[ r
3
] & 0x0000ff0000000000) == 0) GR[ r
1
] = 2;
else if ((GR[ r
3
] & 0x000000ff00000000) == 0) GR[ r
1
] = 3;
else if ((GR[ r
3
] & 0x00000000ff000000) == 0) GR[ r
1
] = 4;
else if ((GR[ r
3
] & 0x0000000000ff0000) == 0) GR[ r
1
] = 5;
else if ((GR[ r
3
] & 0x000000000000ff00) == 0) GR[ r
1
] = 6;
else if ((GR[ r
3
] & 0x00000000000000ff) == 0) GR[ r
1
] = 7;
else GR[ r
1
] = 8;
} else { // right_form scan from least significant up
if ((GR[ r
3
] & 0x00000000000000ff) == 0) GR[ r
1
] = 0;
else if ((GR[ r
3
] & 0x000000000000ff00) == 0) GR[ r
1
] = 1;
else if ((GR[ r
3
] & 0x0000000000ff0000) == 0) GR[ r
1
] = 2;
else if ((GR[ r
3
] & 0x00000000ff000000) == 0) GR[ r
1
] = 3;
else if ((GR[ r
3
] & 0x000000ff00000000) == 0) GR[ r
1
] = 4;
else if ((GR[ r
3
] & 0x0000ff0000000000) == 0) GR[ r
1
] = 5;
else if ((GR[ r
3
] & 0x00ff000000000000) == 0) GR[ r
1
] = 6;
else if ((GR[ r
3
] & 0xff00000000000000) == 0) GR[ r
1
] = 7;
else GR[ r
1
] = 8;
}
} else { // two_byte_form
if (left_form) { // scan from most significant down
if ((GR[ r
3
] & 0xffff000000000000) == 0) GR[ r
1
] = 0;
else if ((GR[ r
3
] & 0x0000ffff00000000) == 0) GR[ r
1
] = 1;
else if ((GR[ r
3
] & 0x00000000ffff0000) == 0) GR[ r
1
] = 2;
else if ((GR[ r
3
] & 0x000000000000ffff) == 0) GR[ r
1
] = 3;
else GR[ r
1
] = 4;
} else { // right_form scan from least significant up
if ((GR[ r
3
] & 0x000000000000ffff) == 0) GR[ r
1
] = 0;
else if ((GR[ r
3
] & 0x00000000ffff0000) == 0) GR[ r
1
] = 1;
Table 2-21. Result Ranges for czx
Size Element Width
Range of Result if Zero Element
Found
Default Result if No Zero Element
Found
1 8 bit 0-7 8
2 16 bit 0-3 4