Graduate Institute of Electronics Engineering, NTUaccess.ee.ntu.edu.tw/course/SOC2004/SOC實驗教材... · System models development board DWARF: ... ARM9E, ARM10, Jazelle, StrongARMand

ACCESS IC LAB

Graduate Institute of Electronics Engineering, NTU

Code DevelopmentCode Development

Speaker: Lung-Hao Chang 張龍豪Directed by Prof. Andy Wu 吳安宇

March, 19, 2003

ACCESS IC LAB Graduate Institute of Electronics Engineering, NTU

SoC Design Laboratory PP. 103/19/2003

Goal of This LabGoal of This LabØ Familiarize with ARM software development tools: ARM

Development Suite (ADS)qProject managementqConfiguring the settings of build targets for your project

Ø Writing code for ARM-based platform designØ Mixed instruction sets, ARM and Thumb interworking, is

learned to balance the performance and code density of an application.



OutlineOutlineØ Basic Code DevelopmentØ ARM/Thumb Interworking



The Structure of ARM ToolsThe Structure of ARM ToolsC/C++ source C libraries asm source

object libraries

C compiler assembler

linker Librarian

.oELF object file

With DWARF2 debug tables

.axfELF/DWARF2 image

debug

ARMsd

ARMulator

System models

developmentboard

ELF: Executable and linking formatDWARF: Debug With Arbitrary Record Format



Main Components in ADS (1/2)Main Components in ADS (1/2)Ø ANSI C compilers – armcc and tccØ ISO/Embedded C++ compilers – armcpp and tcppØ ARM/Thumb assembler - armasmØ Linker - armlinkØ Project management tool for windows - CodeWarriorØ Instruction set simulator - ARMulatorØ Debuggers - AXD, ADW, ADU and armsdØ Format converter - fromelfØ Librarian – armarØ ARM profiler - armprof

ADS: ARM Developer Suite



Main Components in ADS (2/2)Main Components in ADS (2/2)Ø C and C++ librariesØ ROM-based debug tools (ARM Firmware Suite, AFS)Ø Real Time Debug and Trace support Ø Support for all ARM cores and processors including

ARM9E, ARM10, Jazelle, StrongARM and Intel Xscale



View in View in CodeWarrierCodeWarrierØ The CodeWarrior IDE provides a simple, versatile,

graphical user interface for managing your software development projects.

Ø Develop C, C++, and ARM assembly language codeØ targeted at ARM and Thumb processors.Ø It speeds up your build cycle by providing:qcomprehensive project management capabilitiesqcode navigation routines to help you locate routines

quickly.



CodeWarrior DesktopCodeWarrior DesktopToolbarMenu Create a new project

Project Files view

Target Settings

Editor windows



Views in AXDViews in AXDØ Various views allow you to examine and control the

processes you are debugging.Ø In the main menu bar, two menus contain items that

display views:qThe items in the Processor Views menu display views

that apply to the current processor onlyqThe items in the System Views menu display views that

apply to the entire, possibly multiprocessor, target system

AXD: the ARM eXtended Debugger



AXD DesktopAXD DesktopToolbarMenu

Status bar

Disassembly processor view

Source processor view

Console processor view

Control System view

Control System view

Variable processor view

Watch processor view

Watch system view



ARM Emulator: ARM Emulator: ARMulatorARMulator (1/2)(1/2)Ø A suite of programs that models the behavior of various

ARM processor cores and system architecture in software on a host system

Ø Can be operates at various levels of accuracyq Instruction accurateqCycle accurateqTiming accurate



ARM Emulator: ARM Emulator: ARMulatorARMulator (2/2)(2/2)Ø Benchmarking before hardware is availableq Instruction count or number of cycles can be measured

for a program.qPerformance analysis.

Ø Run software on ARMulatorqThrough ARMsd or ARM GUI debuggers, e.g., AXDqThe processor core model incorporates the remote

debug interface, so the processor and the system state are visible from the ARM symbolic debugger

qSupports a C library to allow complete C programs to run on the simulated system



ARM Symbolic DebuggerARM Symbolic DebuggerØ ARMsd: ARM and Thumb symbolic debuggerq can single-step through C or assembly language sources, q set break-points and watch-points, and q examine program variables or memory

Ø It is a front-end interface to debug program running eitherq under emulation (on the ARMulator) orq remotely on a ARM development board (via a serial line or

through JTAG test interface) Ø It allows the setting ofq breakpoints, addresses in the codeq watchpoints, memory address if accessed as data addressè cause exception to halt so that the processor state can be

examined



Basic Debug RequirementsBasic Debug RequirementsØ Control of program executionqset watchpoints on interesting data accessesqset breakpoints on interesting instructionsqsingle step through code

Ø Examine and change processor stateq read and write register values

Ø Examine and change system stateqaccess to system memoryvdownload initial code



Debugger (1/2)Debugger (1/2)Ø A debugger is software that enables you to make use of a debug

agent in order to examine and control the execution of software running on a debug target

Ø Different forms of the debug targetq early stage of product development, softwareq prototype, on a PCB including one or more processorsq final product

Ø The debugger issues instructions that canq load software into memory on the targetq start and stop execution of that softwareq display the contents of memory, registers, and variablesq allow you to change stored values

Ø A debug agent performs the actions requested by the debugger, such asq setting breakpointsq reading from / writing to memory



Debugger (2/2)Debugger (2/2)

Ø Examples of debug agentsq Multi-ICEq Embedded ICEq ARMulatorq BATSq Angle

Ø Remote Debug Interface (RDI) is an open ARM standard procedural interface between a debugger and the debug agent

RDI

Targetemulated in

Software

ARMulatorRDI

Targetemulated in

Software

BATSRDI

ARMdevelopment

board

Multi-ICE

ARMdevelopment

board

RDIRemote_A

Angel

Target (software) Target (hoftware)

Remote Debug Interface (RDI)

ARM debuggerAxD

RDI



Program DesignProgram DesignØ Start with understanding the requirements, translate the

requirements into an unambiguous specificationsØ Define a program structure, the data structure and the

algorithms that are used to perform the required operations on the data

Ø The algorithms may be expressed in pseudo-codeØ Individual modules should be coded, tested and

documentedØ Nearly all programming is based on high-level

languages, however it may be necessary to develop small software components in assembly language to get the best performance



OutlineOutlineØ Basic Code DevelopmentØ ARM/Thumb Interworking



ARM Instruction SetsARM Instruction SetsØ ARM processor is a 32-bit architecture, most ARM’s

implement two instruction setsq32-bit ARM instruction setq16-bit Thumb instruction set



ARM and Thumb Code SizeARM and Thumb Code Size

Simple C routineif (x>=0)

return x;else

return -x;

The equivalent ARM assemblyIabs CMP r0,#0 ;Compare r0 to zero

RSBLT r0,r0,#0 ;If r0<0 (less than=LT) then do r0= 0-r0MOV pc,lr ;Move Link Register to PC (Return)

The equivalent Thumb assemblyCODE16 ;Directive specifying 16-bit (Thumb) instructions

iabs CMP r0,#0 ;Compare r0 to zeroBGE return ;Jump to Return if greater or

;equal to zeroNEG r0,r0 ;If not, negate r0

return MOV pc,lr ;Move Link register to PC (Return)



The Need for The Need for InterworkingInterworkingØ The code density of Thumb and its performance from narrow

memory make it ideal for the bulk of C code in many systems. However there is still a need to change between ARM and Thumb state within most applications:q ARM code provides better performance from wide memoryv therefore ideal for speed-critical parts of an application

q some functions can only be performed with ARM instructions, e.g.vaccess to CPSR (to enable/disable interrupts & to change mode)vaccess to coprocessors

q exception HandlingvARM state is automatically entered for exception handling, but

system specification may require usage of Thumb code for main handler

q simple standalone Thumb programs will also need an ARM assembler header to change state and call the Thumb routine



InterworkingInterworking InstructionsInstructionsØ Interworking is achieved using the Branch Exchange

instructionsq in Thumb state

BX Rnq in ARM state (on Thumb-aware cores only)

BX<condition> Rnwhere Rn can be any registers (r0 to r15)

Ø This performs a branch to an absolute address in 4GB address space by copying Rn to the program counter

Ø Bit 0 of Rn specifies the state to be changed to



Switching between StatesSwitching between States

For most instruction generated by compiler:• Conditional execution is not used• Source and destination registers identical• Only Low registers used• Constants are of limited size• Inline barrel shifter not used16-bit Thumb instruction

32-bit ARM instructionADDS r2,r2,#1

ADD r2,#1

031

15 0



ExampleExample;start off in ARM state

CODE32ADR r0,Into_Thumb+1 ;generate branch target

;address & set bit 0,;hence arrive Thumb state

BX r0 ;branch exchange to Thumb…CODE16 ;assemble subsequent as

;ThumbInto_Thumb …

ADR r5,Back_to_ARM ;generate branch target to;word-aligned address,;hence bit 0 is cleared.

BX r5 ;branch exchange to ARM…CODE32 ;assemble subsequent as

;ARMBack_to_ARM …



ARM/Thumb ARM/Thumb InterworkingInterworking between between C/C++ and ASMC/C++ and ASM

Ø C code compiled to run in one state may call assembler to execute in the other state, and vice-versa. q If the callee is in C, compile it using –apcs /interworkq If the callee is in ASM, assemble it using –apcs

/interwork and return using BX LRØ Any assembler code used in this manner must conform

to ATPCS where appropriate, e.g., function parameters passed in r0-r3 & r12 corruptible



InterworkingInterworking CallsCalls

Thumb-Thumb calls permitted

Non-interworkingThumb code

Non-interworkingARM code

InterworkingThumb code

InterworkingARM code

No calls possible

ARM-ARMcalls permitted

ARM-Thumbcalls permitted

Non-interworking to interworkingARM/Thumb calls permitted

Modules that are compiled for interworking generate slightly larger code, typically 2% larger for Thumb and less than 1% larger for ARM.

Graduate Institute of Electronics Engineering, NTUaccess.ee.ntu.edu.tw/course/SOC2004/SOC實驗教材... · System models development board DWARF: ... ARM9E, ARM10, Jazelle, StrongARMand

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