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IAR Embedded Workbench for RX 5.20

Creating assembler source with CFI support

In this section:

The recommended way to create an assembler language routine that handles call frame information correctly is to start with an assembler language source file created by the compiler.

  1. Start with suitable C source code, for example:

    int F(int);
int cfiExample(int i)
{
  return i + F(i);
}

  2. Compile the C source code, and make sure to create a list file that contains call frame information—the CFI directives.

    Danger

    On the command line, use the option -lA.

    Caution

    In the IDE, choose Project>Options>C/C++ Compiler>List and make sure the suboption Include call frame information is selected.

    For the source code in this example, the list file looks like this, after it has been cleaned up for increased readability:

        NAME cfiExample

    EXTERN _F

    PUBLIC _cfiExample
        
    CFI Names cfiNames0
    CFI StackFrame CFA SP DATA
    CFI VirtualResource ?RET:32
    CFI Resource R1:32, R2:32, R3:32, R4:32, R5:32, R6:32, R7:32, R8:32
    CFI Resource R9:32, R10:32, R11:32, R12:32, R13:32, R14:32, R15:32
    CFI Resource SP:32
    CFI EndNames cfiNames0
        
    CFI Common cfiCommon0 Using cfiNames0
    CFI CodeAlign 1
    CFI DataAlign 1
    CFI ReturnAddress ?RET CODE
    CFI CFA SP+4
    CFI ?RET Frame(CFA, -4)
    CFI R1 Undefined
    CFI R2 Undefined
    CFI R3 Undefined
    CFI R4 Undefined
    CFI R5 Undefined
    CFI R6 SameValue
    CFI R7 SameValue
    CFI R8 SameValue
    CFI R9 SameValue
    CFI R10 SameValue
    CFI R11 SameValue
    CFI R12 SameValue
    CFI R13 SameValue
    CFI R14 Undefined
    CFI R15 Undefined
    CFI EndCommon cfiCommon0
    
    SECTION .text:CODE:NOROOT(0)
    CFI Block cfiBlock0 Using cfiCommon0
    CFI Function _cfiExample
    CODE
_cfiExample:
    PUSH.L    R6
    CFI R6 Frame(CFA, -8)
    CFI CFA SP+8
    MOV.L     R1,R6
    BSR.A     _F
    ADD       R1,R6
    MOV.L     R6,R1
    RTSD      #0x4,R6,R6
    CFI EndBlock cfiBlock0

    END

    Note

    The header file cfi.m contains the macros XCFI_NAMES and XCFI_COMMON, which declare a typical names block and a typical common block. These two macros declare several resources, both concrete and virtual.