g% cat /tmp/x.go
package p

type T [1]*byte

g% go tool 6g -S /tmp/x.go
...
type.[]*uint8 t=7 dupok size=80 value=0
    0x0000 18 00 00 00 00 00 00 00 85 cd 8f fc 00 08 08 17  ................
    0x0010 00 00 00 00 00 00 00 00 48 84 44 00 00 00 00 00  ........H.D.....
    0x0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    0x0030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    0x0040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    rel 16+8 t=1 runtime.algarray+272
    rel 40+8 t=1 go.string."[]*uint8"+0
    rel 56+8 t=1 go.weak.type.*[]*uint8+0
    rel 64+8 t=1 runtime.zerovalue+0
    rel 72+8 t=1 type.*uint8+0

[]*uint8 is a 3-word structure, so the type bitmap is supposed to be inlined, and it is
supposed to be repeated. The type bitmap is visible at offset 0x18 of the type
structure. It is 488444. That's not a doubling. It looks like it should be 488488.

This needs a test that detects the bug, and then it needs a fix.