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cmd/compile: bad line number assigned to instruction loading value into argument register #48546

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aarzilli opened this issue Sep 22, 2021 · 0 comments
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@aarzilli aarzilli commented Sep 22, 2021

This worked correctly in go1.16 but doesn't in 1.17 or on tip at:

go version devel go1.18-051df0d722 Wed Sep 22 03:45:00 2021 +0000 linux/amd64

When compiling https://play.golang.org/p/zUNR4CgABnt with -gcflags=-N -l the inner loop is compiled to:

(...)
test.go:38 | S | 0x47faec | MOVQ 0x48(SP), AX
test.go:38 |   | 0x47faf1 | CALL main.intToInterval(SB)
test.go:38 |   | 0x47faf6 | MOVQ AX, 0x60(SP)
test.go:38 |   | 0x47fafb | JMP 0x47faff
test.go:40 |   | 0x47fafd | JMP 0x47faff
test.go:40 | S | 0x47faff | CMPQ $0x0, 0x60(SP)
test.go:40 |   | 0x47fb05 | JNE 0x47fb0c
test.go:40 |   | 0x47fb07 | JMP 0x47fba4
test.go:35 | S | 0x47fb0c | MOVQ 0x60(SP), CX
test.go:41 | S | 0x47fb11 | MOVQ 0x58(SP), BX
test.go:41 |   | 0x47fb16 | LEAQ type..eq.main.interval+39776(SB), AX
test.go:41 |   | 0x47fb1d | NOPL 0(AX)
test.go:41 | S | 0x47fb20 | CALL runtime.mapassign_fast64ptr(SB)
(...)

I believe the instruction at 0x47fb0c is simply loading interval into an argfument of runtime.mapassign_fast64ptr, however it gets assigned to line 35 which is the declaration of interval, outside of the loop.

cc @dr2chase

@dr2chase dr2chase self-assigned this Sep 22, 2021
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