what is meaning of .prologue in a smali file?

Question

I diassembled a simple android app using apktool and it generated some smali codes.other things are understandable but i am not getting the meaning of .prologue in the smali code.please help me

Here other variables are self understanding linke invoke and locals but what does this .prologue do??

    # direct methods
    .method public constructor <init>()V
        .locals 0

        .prologue  # What does this do?
        .line 17
        invoke-direct {p0}, Landroid/app/Activity;-><init>()V

        return-void
    .end method

Answer 1

This is equivalent to the DBG_SET_PROLOGUE_END debug opcode in the dex file, as documented here.

sets the prologue_end state machine register, indicating that the next position entry that is added should be considered the end of a method prologue (an appropriate place for a method breakpoint). The prologue_end register is cleared by any special (>= 0x0a) opcode.