Atmel CAVR-4 Manual De Usuario

CAVR-4

Part1. Using the compiler

Note: In this example we use a low optimization level when compiling the code to 
show local and global variable access. If a higher level of optimization is used, the 
required references to local variables could be removed during the optimization. The 
actual function declaration is not changed by the optimization level.

In IAR Embedded Workbench, specify list options on file level. Select the file in the 
workspace window. Then choose Project>Options. In the C/C++ Compiler category, 
select Override inherited settings. On the List page, deselect Output list file, and 
instead select the Output assembler file option and its suboption Include source. Also, 
be sure to specify a low level of optimization.

Use the following options to compile the skeleton code:

iccavr skeleton -lA .

The 

-lA

 option creates an assembler language output file including C or C++ source 

lines as assembler comments. The 

.

 (period) specifies that the assembler file should be 

named in the same way as the C or C++ module (

skeleton

), but with the filename 

extension 

s90

. Also remember to specify the memory model you are using as well as a 

low level of optimization.

The result is the assembler source output file 

skeleton.s90

.

Note: The 

-lA

 option creates a list file containing call frame information (

CFI)

 

directives, which can be useful if you intend to study these directives and how they are 
used. If you only want to study the calling convention, you can exclude the 

CFI

 

directives from the list file. In IAR Embedded Workbench, select 
Project>Options>C/C++ Compiler>List and deselect the suboption Include call 
frame information. On the command line, use the option 

-lB

 instead of 

-lA

. Note that 

CFI

 information must be included in the source code to make the C-SPY Call Stack 

window work. 

The output file contains the following important information:

●

The calling convention

●

The return values

●

The global variables

●

The function parameters

●

How to create space on the stack (auto variables)

●

Call frame information (CFI).

The 

CFI

 directives describe the call frame information needed by the Call Stack window 

in the IAR C-SPY™ Debugger.