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.RESTOREREG

Generates either a WOD_SAVE_NONVOL or a WOD_SAVE_NONVOL_FAR unwind code entry for the specified register and offset, using the current epilogue offset.

Syntax

.RESTOREREG reg, offset

Parameters

reg
The nonvolatile register to restore.

offset
The stack offset from which the register is restored.

Remarks

Important

This directive is experimental and is subject to change. Enable Unwind Version 3 by using ml64.exe /unwindv3.

.RESTOREREG is only valid in Unwind Version 3. It's the epilogue counterpart to .SAVEREG.

Microsoft Assembler (MASM) chooses the most efficient encoding for a given offset.

  • .RESTOREREG is only allowed within an epilogue region, between .BEGINEPILOG and .ENDEPILOG.
  • These directives generate unwind metadata (.xdata and .pdata sections) but don't produce executable code.
  • In Unwind Version 3, .RESTOREREG must appear before the instruction that loads the register from the stack.
  • To ensure agreement, wrap both the unwind directives and the code they're meant to unwind in a macro.
  • In Unwind Version 3, epilogue directives are mandatory for epilogue unwind code generation. No epilogue unwind codes are emitted without a .BEGINEPILOG/.ENDEPILOG pair.

Note

In Unwind Version 1, the directive appears after the corresponding instruction. In Unwind Version 3, the directive appears before the instruction.

Example for unwindv3

; ml64 /unwindv3 ex1.asm /link /entry:Example1 /SUBSYSTEM:CONSOLE
_text SEGMENT
Example1 PROC FRAME
   .allocstack 020h
   sub rsp, 020h
   .savereg rbx, 0
   mov [rsp], rbx
   .savereg rsi, 8
   mov [rsp+8], rsi
.endprolog
   ; rest of function ...
   .beginepilog
   .restorereg rsi, 8
   mov rsi, [rsp+8]
   .restorereg rbx, 0
   mov rbx, [rsp]
   .freestack 020h
   add rsp, 020h
   .endepilog
   ret
Example1 ENDP
_text ENDS
END

See also

x64 Unwind Version 3 (experimental)
Directives Reference
.SAVEREG
.BEGINEPILOG
MASM BNF Grammar

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