Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 919

br
br — Branch
( ) br.
Format: qp btype
( ) br.
qp btype
br.
btype
br. .
ph dh target
( ) br.
qp btype
( ) br.
qp btype
br. .
ph dh b
A branch condition is evaluated, and either a branch is taken, or execution continues
Description:
with the next sequential instruction. The execution of a branch logically follows the
execution of all previous non-branch instructions in the same instruction group. On a
taken branch, execution begins at slot 0.
Branches can be either IP-relative, or indirect. For IP-relative branches, the
operand, in assembly, specifies a label to branch to. This is encoded in the branch
instruction as a signed immediate displacement (
the bundle containing this instruction (
the target address is taken from BR
Table 2-6.
btype
cond or none
call
ret
ia
cloop
ctop, cexit
wtop, wexit
There are two pseudo-ops for unconditional branches. These are encoded like a
conditional branch (btype = cond), with the
hint of sptk.
The branch type determines how the branch condition is calculated and whether the
branch has other effects (such as writing a link register). For the basic branch types,
3:20
. . .
bwh ph dh target
25
. . . =
bwh ph dh b target
1 25
. . .
bwh ph dh target
25
25
. . .
bwh ph dh b
2
. . . =
bwh ph dh b b
1 2
2
Branch Types
Function
Conditional branch
Conditional procedure call
Conditional procedure return
Invoke IA-32 instruction set
Counted loop branch
Mod-scheduled counted loop
Mod-scheduled while loop
call_form, ip_relative_form
counted_form, ip_relative_form
call_form, indirect_form
) between the target bundle and
imm
21
= - IP >> 4). For indirect branches,
imm target
21 25
.
b
2
Branch Condition
Qualifying predicate
Qualifying predicate
Qualifying predicate
Unconditional
Loop count
Loop count and epilog
count
Qualifying predicate and
epilog count
field specifying PR 0, and with the bwh
qp
ip_relative_form B1
B3
B2
pseudo-op
indirect_form B4
B5
pseudo-op
target
25
Target Address
IP-rel or Indirect
IP-rel or Indirect
Indirect
Indirect
IP-rel
IP-rel
IP-rel
Volume 3: Instruction Reference