understand `godebug` at all.)

The defaults from the `go` and `godebug` lines apply to all main
packages that are built. For more fine-grained control,
starting in Go 1.21, a main package's source files
can include one or more `//go:debug` directives at the top of the file
(preceding the `package` statement).
The `godebug` lines in the previous example would be written:

	//go:debug default=go1.21

// Small moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (MOVBstore dst (MOVBload src mem) mem)
(Move [2] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore dst (MOVHload src mem) mem)
(Move [2] dst src mem) =>
	(MOVBstore [1] dst (MOVBload [1] src mem)
		(MOVBstore dst (MOVBload src mem) mem))
(Move [4] {t} dst src mem) && t.Alignment()%4 == 0 =>

pkg os, method (FileMode) Perm() FileMode
pkg os, method (FileMode) String() string
pkg os, type FileInfo interface { IsDir, ModTime, Mode, Name, Size, Sys }
pkg os, type FileInfo interface, IsDir() bool
pkg os, type FileInfo interface, ModTime() time.Time
pkg os, type FileInfo interface, Mode() FileMode
pkg os, type FileInfo interface, Name() string
pkg os, type FileInfo interface, Size() int64

		mem)

// moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (MOVBstore dst (MOVBload src mem) mem)
(Move [2] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore dst (MOVHload src mem) mem)
(Move [2] dst src mem) =>
	(MOVBstore [1] dst (MOVBload [1] src mem)
		(MOVBstore dst (MOVBload src mem) mem))
(Move [4] {t} dst src mem) && t.Alignment()%4 == 0 =>

		mem)

// moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (MOVBstore dst (MOVBload src mem) mem)
(Move [2] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore dst (MOVHload src mem) mem)
(Move [2] dst src mem) =>
	(MOVBstore [1] dst (MOVBload [1] src mem)
		(MOVBstore dst (MOVBload src mem) mem))
(Move [4] {t} dst src mem) && t.Alignment()%4 == 0 =>

		mem)

// moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (MOVBstore dst (MOVBUload src mem) mem)
(Move [2] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore dst (MOVHUload src mem) mem)
(Move [2] dst src mem) =>
	(MOVBstore [1] dst (MOVBUload [1] src mem)
		(MOVBstore dst (MOVBUload src mem) mem))
(Move [4] {t} dst src mem) && t.Alignment()%4 == 0 =>

pkg encoding/csv, method (*Reader) FieldPos(int) (int, int)
pkg go/build, type Context struct, ToolTags []string
pkg go/parser, const SkipObjectResolution = 64
pkg go/parser, const SkipObjectResolution Mode
pkg image, method (*Alpha) RGBA64At(int, int) color.RGBA64
pkg image, method (*Alpha) SetRGBA64(int, int, color.RGBA64)
pkg image, method (*Alpha16) RGBA64At(int, int) color.RGBA64

// Lowering moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (I64Store8 dst (I64Load8U src mem) mem)
(Move [2] dst src mem) => (I64Store16 dst (I64Load16U src mem) mem)
(Move [4] dst src mem) => (I64Store32 dst (I64Load32U src mem) mem)
(Move [8] dst src mem) => (I64Store dst (I64Load src mem) mem)
(Move [16] dst src mem) =>
	(I64Store [8] dst (I64Load [8] src mem)