3:32
Volume 3: Instruction Reference
brp
brp — Branch Predict
Format:
brp.
ipwh
.
ih target
25
,
tag
13
ip_relative_form
brp.
indwh
.
ih b
2
,
tag
13
indirect_form
brp.ret.
indwh
.
ih b
2
,
tag
13
return_form, indirect_form
Description:
This instruction can be used to provide to hardware early information about a future
branch. It has no effect on architectural machine state, and operates as a
nop
instruction except for its performance effects.
The
tag
13
operand, in assembly, specifies the address of the branch instruction to which
this prediction information applies. This is encoded in the branch predict instruction as a
signed immediate displacement (
timm
9
) between the bundle containing the presaged
branch and the bundle containing this instruction (
timm
9
=
tag
13
- IP >> 4).
The
target
25
operand, in assembly, specifies the label that the presaged branch will have
as its target. This is encoded in the branch predict instruction exactly as in branch
instructions, with a signed immediate displacement (
imm
21
) between the target bundle
and the bundle containing this instruction (
imm
21
=
target
25
- IP >> 4). The indirect_form
can be used to presage an indirect branch. In the indirect_form, the target of the
presaged branch is given by BR
b
2
.
The return_form is used to indicate that the presaged branch will be a return.
Other hints can be given about the presaged branch. Values for various hint completers
are shown in the following tables. For more details, refer to
Prediction Hints” on page 1:78
The
ipwh
and
indwh
completers provide information about how best the branch condition
should be predicted, when the branch is reached.
The
ih
completer can be used to mark a small number of very important branches (e.g.,
an inner loop branch). This can signal to hardware to use faster, smaller prediction
structures for this information.
Table 2-11.
IP-relative Branch Predict Whether Hint
ipwh
Completer
IP-relative Branch Predict Whether Hint
sptk
Presaged branch should be predicted Static Taken
loop
Presaged branch will be
br.cloop
,
br.ctop
, or
br.wtop
exit
Presaged branch will be
br.cexit
or
br.wexit
dptk
Presaged branch should be predicted Dynamically
Table 2-12.
Indirect Branch Predict Whether Hint
indwh
Completer
Indirect Branch Predict Whether Hint
sptk
Presaged branch should be predicted Static Taken
dptk
Presaged branch should be predicted Dynamically
Table 2-13.
Importance Hint
ih
Completer
Branch Predict Importance Hint
none
Less important
imp
More important
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...