cmd/compile: deduping of panicindex calls on the same line appears broken

[josharian]

Run go tool compile -S fannkuch_test.go 2>&1 | grep -c "CALL.*panicindex". This yields 9 on 1.8.1 and 13 on tip. It appears that the panicindex-on-same-line deduping is broken; the extra panicindex calls are all duplicates. Tip output:

	0x00ef 00239 (fannkuch_test.go:23)	CALL	runtime.panicindex(SB)
	0x0130 00304 (fannkuch_test.go:34)	CALL	runtime.panicindex(SB)
	0x0191 00401 (fannkuch_test.go:40)	CALL	runtime.panicindex(SB)
	0x0198 00408 (fannkuch_test.go:40)	CALL	runtime.panicindex(SB)
	0x01ed 00493 (fannkuch_test.go:45)	CALL	runtime.panicindex(SB)
	0x01f4 00500 (fannkuch_test.go:45)	CALL	runtime.panicindex(SB)
	0x026d 00621 (fannkuch_test.go:65)	CALL	runtime.panicindex(SB)
	0x0274 00628 (fannkuch_test.go:65)	CALL	runtime.panicindex(SB)
	0x02d4 00724 (fannkuch_test.go:68)	CALL	runtime.panicindex(SB)
	0x02db 00731 (fannkuch_test.go:67)	CALL	runtime.panicindex(SB)
	0x02e7 00743 (fannkuch_test.go:49)	CALL	runtime.panicindex(SB)
	0x02fd 00765 (fannkuch_test.go:37)	CALL	runtime.panicindex(SB)
	0x0313 00787 (fannkuch_test.go:37)	CALL	runtime.panicindex(SB)

[dr2chase]

Is this perhaps an artifact of enhanced positions that are now more than just a line?

[josharian]

Probably, yes. Haven't dug yet, but plan to today.

[gopherbot]

CL https://golang.org/cl/43291 mentions this issue.