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cmd/compile: crash in regalloc #15585

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MichaelTJones opened this issue May 6, 2016 · 4 comments
Closed

cmd/compile: crash in regalloc #15585

MichaelTJones opened this issue May 6, 2016 · 4 comments
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Go1.7

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@MichaelTJones
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Please answer these questions before submitting your issue. Thanks!

  1. What version of Go are you using (go version)?
    go version devel +83676d6 Fri May 6 19:27:45 2016 +0000 darwin/amd64

  2. What operating system and processor architecture are you using (go env)?
    $ go env
    GOARCH="amd64"
    GOBIN=""
    GOEXE=""
    GOHOSTARCH="amd64"
    GOHOSTOS="darwin"
    GOOS="darwin"
    GOPATH="/Users/mtj/gocode"
    GORACE=""
    GOROOT="/Users/mtj/go"
    GOTOOLDIR="/Users/mtj/go/pkg/tool/darwin_amd64"
    CC="clang"
    GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/6w/y_5pxjsx4h1dhpyrlgq70qt80000gn/T/go-build580720697=/tmp/go-build -gno-record-gcc-switches -fno-common"
    CXX="clang++"
    CGO_ENABLED="1"

  3. What did you do?
    Compiled after a trivial change to a working program.
    https://play.golang.org/p/G4wvi6aza1
    put in a directory, build ==> compiler dies.

  4. What did you expect to see?
    happiness

  5. What did you see instead?

    $ go build bug.go
    # command-line-arguments
    ./bug.go:9: internal compiler error: panic during regalloc while compiling example:

    runtime error: index out of range

    goroutine 1 [running]:
    cmd/compile/internal/ssa.Compile.func1(0xc8204c8e08, 0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/compile.go:35 +0xab
    panic(0x47aa20, 0xc820010140)
    /Users/mtj/go/src/runtime/panic.go:458 +0x226
    cmd/compile/internal/ssa.(*regAllocState).regalloc(0xc8200d6780, 0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/regalloc.go:1324 +0x4311
    cmd/compile/internal/ssa.regalloc(0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/regalloc.go:134 +0x64
    cmd/compile/internal/ssa.Compile(0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/compile.go:64 +0x2cb
    cmd/compile/internal/gc.buildssa(0xc820417ef0, 0x0)
    /Users/mtj/go/src/cmd/compile/internal/gc/ssa.go:228 +0x8b8
    cmd/compile/internal/gc.compile(0xc820417ef0)
    /Users/mtj/go/src/cmd/compile/internal/gc/pgen.go:405 +0x12f9
    cmd/compile/internal/gc.funccompile(0xc820417ef0)
    /Users/mtj/go/src/cmd/compile/internal/gc/dcl.go:1278 +0x178
    cmd/compile/internal/gc.Main()
    /Users/mtj/go/src/cmd/compile/internal/gc/main.go:464 +0x1953
    cmd/compile/internal/amd64.Main()
    /Users/mtj/go/src/cmd/compile/internal/amd64/galign.go:96 +0x381
    main.main()
    /Users/mtj/go/src/cmd/compile/main.go:33 +0x286

    goroutine 1 [running]:
    runtime/debug.Stack(0x0, 0x0, 0x0)
    /Users/mtj/go/src/runtime/debug/stack.go:24 +0x6f
    cmd/compile/internal/gc.Fatalf(0x4cad80, 0x2c, 0xc8204f8040, 0x4, 0x4)
    /Users/mtj/go/src/cmd/compile/internal/gc/subr.go:158 +0x236
    cmd/compile/internal/gc.(_ssaExport).Fatalf(0x710ae8, 0xc800000009, 0x4cad80, 0x2c, 0xc8204f8040, 0x4, 0x4)
    /Users/mtj/go/src/cmd/compile/internal/gc/ssa.go:4398 +0x65
    cmd/compile/internal/ssa.(_Config).Fatalf(0xc82044c000, 0x9, 0x4cad80, 0x2c, 0xc8204f8040, 0x4, 0x4)
    /Users/mtj/go/src/cmd/compile/internal/ssa/config.go:181 +0x64
    cmd/compile/internal/ssa.(_Func).Fatalf(0xc82001a3c0, 0x4cad80, 0x2c, 0xc8204f8040, 0x4, 0x4)
    /Users/mtj/go/src/cmd/compile/internal/ssa/func.go:393 +0x61
    cmd/compile/internal/ssa.Compile.func1(0xc8204c8e08, 0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/compile.go:37 +0x23e
    panic(0x47aa20, 0xc820010140)
    /Users/mtj/go/src/runtime/panic.go:458 +0x226
    cmd/compile/internal/ssa.(_regAllocState).regalloc(0xc8200d6780, 0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/regalloc.go:1324 +0x4311
    cmd/compile/internal/ssa.regalloc(0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/regalloc.go:134 +0x64
    cmd/compile/internal/ssa.Compile(0xc82001a3c0)
    /Users/mtj/go/src/cmd/compile/internal/ssa/compile.go:64 +0x2cb
    cmd/compile/internal/gc.buildssa(0xc820417ef0, 0x0)
    /Users/mtj/go/src/cmd/compile/internal/gc/ssa.go:228 +0x8b8
    cmd/compile/internal/gc.compile(0xc820417ef0)
    /Users/mtj/go/src/cmd/compile/internal/gc/pgen.go:405 +0x12f9
    cmd/compile/internal/gc.funccompile(0xc820417ef0)
    /Users/mtj/go/src/cmd/compile/internal/gc/dcl.go:1278 +0x178
    cmd/compile/internal/gc.Main()
    /Users/mtj/go/src/cmd/compile/internal/gc/main.go:464 +0x1953
    cmd/compile/internal/amd64.Main()
    /Users/mtj/go/src/cmd/compile/internal/amd64/galign.go:96 +0x381
    main.main()
    /Users/mtj/go/src/cmd/compile/main.go:33 +0x286
@bradfitz bradfitz changed the title Crash in go compiler at tip cmd/compile: crash in regalloc May 6, 2016
@bradfitz bradfitz added this to the Go1.7 milestone May 6, 2016
@dr2chase
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dr2chase commented May 6, 2016

@randall77 - have you started on this?
Seems to be failure to guard some sparse set ops, though there may be a root cause we need to look at:

diff --git a/src/cmd/compile/internal/ssa/sparsemap.go b/src/cmd/compile/internal/ssa/sparsemap.go
index 0211a70..e22ed1e 100644
--- a/src/cmd/compile/internal/ssa/sparsemap.go
+++ b/src/cmd/compile/internal/ssa/sparsemap.go
@@ -67,6 +67,9 @@ func (s *sparseMap) setBit(k ID, v uint) {
 }

 func (s *sparseMap) remove(k ID) {
+       if k >= ID(len(s.sparse)) {
+               return
+       }
        i := s.sparse[k]
        if i < len(s.dense) && s.dense[i].key == k {
                y := s.dense[len(s.dense)-1]
diff --git a/src/cmd/compile/internal/ssa/sparseset.go b/src/cmd/compile/internal/ssa/sparseset.go
index 66bebf1..f018563 100644
--- a/src/cmd/compile/internal/ssa/sparseset.go
+++ b/src/cmd/compile/internal/ssa/sparseset.go
@@ -53,6 +53,9 @@ func (s *sparseSet) addAllValues(a []*Value) {
 }

 func (s *sparseSet) remove(x ID) {
+       if x >= ID(len(s.sparse)) {
+               return
+       }
        i := s.sparse[x]
        if i < len(s.dense) && s.dense[i] == x {
                y := s.dense[len(s.dense)-1]

@dr2chase
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dr2chase commented May 6, 2016

uh, yeah. We preallocate a sparseset for as many values as we've got, then we create more values.

@dr2chase dr2chase assigned dr2chase and unassigned randall77 May 7, 2016
@MichaelTJones
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Cool! Fixed already!

https://go-review.googlesource.com/22911
Gerrit-Reviewer: Cherry Zhang cherryyz@google.com
Gerrit-Reviewer: David Chase drchase@google.com
Gerrit-Reviewer: Keith Randall khr@golang.org
Gerrit-Reviewer: Russ Cox rsc@golang.org

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CL https://golang.org/cl/22911 mentions this issue.

@golang golang locked and limited conversation to collaborators May 9, 2017
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@bradfitz @dr2chase @randall77 @MichaelTJones @gopherbot