SH-3 Prolog and Epilog Examples

  • 项目

The following examples show how to use prologs and epilogs in specific situations.

  • Allocate a stack frame to save R14, R8, and PR

    The following example allocates a stack frame to save R14, R8, and PR and to allow alloca() calls. In addition, the example allocates a four-word argument build area. It needs no stack space for local variables or temporaries.

    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

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

    The following 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.

    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

  • Allocate a stack frame with 64KB of memory

    The following example allocates a stack frame that requires 64 KB of memory. It saves the argument register R4 to the incoming argument save area, and saves the argument register R5 to allocated register R8. No separate frame pointer is required. This example declares an exception handler.

    EXCEPTION_HANDLER RoutineHandler
NESTED_ENTRY Function

mov.l R4, @R15   // Save argument to incoming argument save area.
mov.l R8, @-R15
sts.l PR, @-R15
mov.l @(0x0000001C,pc),r1   // Load constant -65528.
add     r1,r15        // Allocate stack frame.
mov.l R5, R8        // Save argument to register.

PROLOG_END

// Routine body

mov.l @(0x0000000C,pc),r1   // Load constant 65528.
add     r1,r15        // Remove stack frame.
lds.l @R15+, PR      // Recover return address.
rts
mov.l @R15+, R8     // Restore R8.

ENTRY_END Function

See Also

SH-3 Calling Sequence Specification | SH-3 Prolog and Epilog | SH-3 Prolog | SH-3 Epilog

 Last updated on Thursday, April 08, 2004

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