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cmd/compile: panic: internal error: can't locate after prolog value (with -N -l) #45948

ALTree opened this issue May 4, 2021 · 4 comments


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@ALTree ALTree commented May 4, 2021

$ gotip version
go version devel go1.17-da7496d841 Tue May 4 17:37:39 2021 +0000 linux/amd64
package p

func f(p int) {
	goto L

$ gotip tool compile -N -l crash.go

panic: internal error: f=f: can't locate after prolog value

goroutine 7 [running]:
cmd/compile/internal/ssa.BuildFuncDebugNoOptimized(0xc000172400, 0xc00037cea0, 0x0, 0xd1e2b8)
	/home/alberto/go/src/cmd/compile/internal/ssa/debug.go:1366 +0xf54
cmd/compile/internal/ssagen.genssa(0xc00037cea0, 0xc000402a80)
	/home/alberto/go/src/cmd/compile/internal/ssagen/ssa.go:6988 +0xc16
cmd/compile/internal/ssagen.Compile(0xc0001382c0, 0x0)
	/home/alberto/go/src/cmd/compile/internal/ssagen/pgen.go:175 +0x266
	/home/alberto/go/src/cmd/compile/internal/gc/compile.go:136 +0x65
created by cmd/compile/internal/gc.compileFunctions.func2
	/home/alberto/go/src/cmd/compile/internal/gc/compile.go:134 +0xcf

Doesn't crash on Go1.16.
Doesn't crash on GOEXPERIMENT=noregabiargs.

Reduced from a gosmith crasher.

cc @cherrymui @aclements @dr2chase

@ALTree ALTree added this to the Go1.17 milestone May 4, 2021
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@cherrymui cherrymui commented May 4, 2021

cc @thanm

Maybe we can change it to be best effort.


@thanm thanm self-assigned this May 4, 2021
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@thanm thanm commented May 4, 2021

I'll take a look.


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@gopherbot gopherbot commented May 4, 2021

Change mentions this issue: cmd/compile: handle degenerate entry blocks in -N debug gen


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@gopherbot gopherbot commented May 5, 2021

Change mentions this issue: cmd/compile: debug trace output for -N variable location gen


@gopherbot gopherbot closed this in 66ce8aa May 5, 2021
gopherbot pushed a commit that referenced this issue May 5, 2021
Add some rudimentary debug trace output for -N location list
generation if "-d=ssa/locationlists" is set.

Updates #45948.

Change-Id: If1a95730538a6e7def7ebe1ece1a71da8e5f0975
Trust: Than McIntosh <>
Run-TryBot: Than McIntosh <>
TryBot-Result: Go Bot <>
Reviewed-by: David Chase <>
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4 participants