SH-4 Prolog and Epilog Examples

9/7/2007

The following code examples show how to use prolog and epilog to perform certain tasks.

• Allocate a stack frame to save R14, R8, and PR
  This example allocates a stack frame to save R14, R8, and PR, and to allow alloca() calls. It also allocates a 4-word argument build area. Local variables and temporaries do not need stack space.

  // Prolog
  
  NESTED_ENTRY Function
  
  mov.l R14, @-R15 // Save old frame pointer.
  mov.l R8, @-R15 // Save a permanent register.
  sts.l PR, @-R15 // Save return address.
  mov  R15, R14  // Set up new frame pointer.
  add  #12, R14
  add  #-16, R15  // Allocate argument save area
  
  PROLOG_END
  
  // Routine body
  
  
  // Epilog
  
  add  #-12, R14  // Find base of RSA.
  mov  R14, R15
  lds.l @R15+, PR  // Restore return address.
  mov.l @R15+, R8  // Restore R8.
  rts        // Return.
   mov.l @R15+, R14 // Restore R14.
  
  ENTRY_END Function
  

• Allocate a stack frame for a leaf routine
  This example allocates a stack frame for a leaf routine that requires 40 bytes for local variables and temporaries. It uses permanent registers R8, R9, and R10. This routine has no _alloca locals, so no frame pointer is required.

  //  Prolog
  
  NESTED_ENTRY Function
  
  mov.l R8, @-R15
  mov.l R9, @-R15
  mov.l R10, @-R15
  add  #-40, R15
  
  PROLOG_END
  
  // Routine body
  
  add  #40, R15
  mov.l @R15+, R10
  mov.l @R15+, R9
  rts
  mov.l @R15+, R8
  
  ENTRY_END Function
  

See Also

Reference

SH-4 Assembler Macros

Other Resources

Renesas SH-4 Prolog and Epilog