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### 7.77 `.loc` fileno lineno`[`column`] [`options`]`

When emitting DWARF2 line number information, the `.loc` directive will add a row to the `.debug_line` line number matrix corresponding to the immediately following assembly instruction. The fileno, lineno, and optional column arguments will be applied to the `.debug_line` state machine before the row is added.

The options are a sequence of the following tokens in any order:

`basic_block`
  This option will set the `basic_block` register in the `.debug_line` state machine to `true`.
`prologue_end`
  This option will set the `prologue_end` register in the `.debug_line` state machine to `true`.
`epilogue_begin`
  This option will set the `epilogue_begin` register in the `.debug_line` state machine to `true`.
`is_stmt` value
  This option will set the `is_stmt` register in the `.debug_line` state machine to `value`, which must be either 0 or 1.
`isa` value
  This directive will set the `isa` register in the `.debug_line` state machine to value, which must be an unsigned integer.
`discriminator` value
  This directive will set the `discriminator` register in the `.debug_line` state machine to value, which must be an unsigned integer.