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cmd/compile: internal error for math.Sqrt as statement rather than expression #16804

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ghost opened this issue Aug 19, 2016 · 6 comments
Closed

cmd/compile: internal error for math.Sqrt as statement rather than expression #16804

ghost opened this issue Aug 19, 2016 · 6 comments
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@ghost
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ghost commented Aug 19, 2016 •
edited by ghost

go version go1.7 darwin/amd64

https://play.golang.org/p/ERICb8NpYL
Don't actually run the playground, this is just the content of the file, make a file called whatever_test.go and try to test it.

    ./a_test.go:10: internal compiler error: unhandled stmt SQRT

    goroutine 1 [running]:
    runtime/debug.Stack(0x0, 0x0, 0x0)
        /usr/local/go/src/runtime/debug/stack.go:24 +0x79
    cmd/compile/internal/gc.Fatalf(0x4fc74c, 0x11, 0xc420456f20, 0x1, 0x1)
        /usr/local/go/src/cmd/compile/internal/gc/subr.go:165 +0x15d
    cmd/compile/internal/gc.(*ssaExport).Unimplementedf(0x75e786, 0xa, 0x4fc74c, 0x11, 0xc420456f20, 0x1, 0x1)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:4446 +0x13e
    cmd/compile/internal/ssa.(*Config).Unimplementedf(0xc4204be000, 0xc40000000a, 0x4fc74c, 0x11, 0xc420456f20, 0x1, 0x1)
        /usr/local/go/src/cmd/compile/internal/ssa/config.go:202 +0x71
    cmd/compile/internal/gc.(*state).Unimplementedf(0xc4200e2240, 0x4fc74c, 0x11, 0xc420456f20, 0x1, 0x1)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:338 +0x83
    cmd/compile/internal/gc.(*state).stmt(0xc4200e2240, 0xc4204b3e60)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:967 +0x9fd
    cmd/compile/internal/gc.(*state).stmts(0xc4200e2240, 0xc4204a3500)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:535 +0x5e
    cmd/compile/internal/gc.(*state).stmt(0xc4200e2240, 0xc4204b3d40)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:891 +0x17c8
    cmd/compile/internal/gc.(*state).stmts(0xc4200e2240, 0xc4204a35a0)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:535 +0x5e
    cmd/compile/internal/gc.buildssa(0xc4204b35f0, 0x0)
        /usr/local/go/src/cmd/compile/internal/gc/ssa.go:182 +0x6c0
    cmd/compile/internal/gc.compile(0xc4204b35f0)
        /usr/local/go/src/cmd/compile/internal/gc/pgen.go:405 +0x1377
    cmd/compile/internal/gc.funccompile(0xc4204b35f0)
        /usr/local/go/src/cmd/compile/internal/gc/dcl.go:1287 +0x186
    cmd/compile/internal/gc.Main()
        /usr/local/go/src/cmd/compile/internal/gc/main.go:467 +0x19f8
    cmd/compile/internal/amd64.Main()
        /usr/local/go/src/cmd/compile/internal/amd64/galign.go:93 +0x2fa
    main.main()
        /usr/local/go/src/cmd/compile/main.go:33 +0x2a3```
@ianlancetaylor ianlancetaylor changed the title go test fails to execute simple test cmd/compile: internal error for math.Sqrt as statement rather than expression Aug 19, 2016
@ianlancetaylor ianlancetaylor modified the milestones: Go1.7.1, Go1.8 Aug 19, 2016
@ianlancetaylor
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Simpler replication:

package main

import (
    "math"
)

func main() {
    math.Sqrt(10)
}

Works if the line in the function is

_ = math.Sqrt(10)

I initially marked this as 1.7.1, but considering that the statement is useless, dropping to 1.8.

CC @randall77 @josharian

@md2perpe
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Bug verified under go version go1.7 windows/amd64.

@josharian
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Should be a straightforward fix. Perhaps @odeke-em @kevinburke or @martisch (or anyone else getting up to speed on the compiler who I might have missed) wants to try their hand? Leave a note here first so you don't collide with each other. :)

@josharian
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Note also (as Ian observes) that the only possible purpose of the statement is to evaluate the internal expression for side effects, so there's no need to generate an actual additional SSA value.

@josharian josharian mentioned this issue Aug 20, 2016
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@martisch
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martisch commented Aug 20, 2016 •
edited

seems:

case OSQRT:
    s.expr(n.Left)

in ssa.go should suffice. Will mail a full CL later.

@gopherbot
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CL https://golang.org/cl/27437 mentions this issue.

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