Program Flow Prediction
ARM DDI 0301H Copyright © 2004-2009 ARM Limited. All rights reserved. 5-11
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MOV PC, entry_point_of_loaded_program
.
.
Compiled BitBlt routines optimize large copy operations by constructing and executing a
copying loop that has been optimized for the exact operation wanted. When writing such a
routine an
IMB
is required between the code that constructs the loop and the actual execution of
the constructed loop. Example 5-2 shows this.
Example 5-2 Running BitBlt code
IMBRange EQU 0xF00001.
.
; code that constructs loop code
; load R0 with the start address of the constructed loop
; load R1 with the end address of the constructed loop
SVC IMBRange
[branch to IMBRange service routine]
[read registers R0 and R1 to set up address range parameters]
[perform processor-specific operations to execute IMBRange]
[within address range]
[return to code]
; start of loop code
.
.
When writing a self-decompressing program, an
IMB
must be issued after the routine that
decompresses the bulk of the code and before the decompressed code starts to be executed.
Example 5-3 shows this.
Example 5-3 Self-decompressing code
IMB EQU 0xF00000
.
.
; copy and decompress bulk of code
SVC IMB
; start of decompressed code
.
.
.
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