cmd/compile: test/inline_sync.go test fails if GOARM64=v8.1

[andreybokhanko]

Go version

trunk

Output of go env in your module/workspace:

GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/home/abokhanko/.cache/go-build"
GOENV="/home/abokhanko/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/abokhanko/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/abokhanko/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/abokhanko/goroot"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/abokhanko/goroot/pkg/tool/linux_arm64"
GOVCS=""
GOVERSION="go1.20.13"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1657645440=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ cd $GOROOT/src
$ GOARM64=v8.1 ../bin/go test cmd/internal/testdir -run=Test/inline_sync.go

What did you see happen?

--- FAIL: Test (0.04s)
    --- FAIL: Test/inline_sync.go (0.41s)
        testdir_test.go:145: exit status 1
            /home/abokhanko/goroot/test/inline_sync.go:26: can inline small5
            /home/abokhanko/goroot/test/inline_sync.go:31: can inline small6
            /home/abokhanko/goroot/test/inline_sync.go:38: can inline small7
            /home/abokhanko/goroot/test/inline_sync.go:45: can inline small8
            /home/abokhanko/goroot/test/inline_sync.go:50: can inline small9
            /home/abokhanko/goroot/test/inline_sync.go:28: inlining call to sync.(*Mutex).Unlock
            /home/abokhanko/goroot/test/inline_sync.go:33: inlining call to sync.(*Mutex).Lock
            /home/abokhanko/goroot/test/inline_sync.go:40: inlining call to sync.(*Once).Do
            /home/abokhanko/goroot/test/inline_sync.go:40: inlining call to atomic.(*Uint32).Load
            /home/abokhanko/goroot/test/inline_sync.go:47: inlining call to sync.(*RWMutex).RUnlock
            /home/abokhanko/goroot/test/inline_sync.go:47: inlining call to atomic.(*Int32).Add
            /home/abokhanko/goroot/test/inline_sync.go:52: inlining call to sync.(*RWMutex).RLock
            /home/abokhanko/goroot/test/inline_sync.go:52: inlining call to atomic.(*Int32).Add
            /home/abokhanko/goroot/test/inline_sync.go:33: internal compiler error: 'small6': if block b1 has non-bool control value v13 = Select0 <uint32> v11

            goroutine 1 [running]:
            runtime/debug.Stack()
                /home/abokhanko/goroot/src/runtime/debug/stack.go:26 +0x64
            cmd/compile/internal/base.FatalfAt({0x4f5408?, 0x40?}, {0x4000022f90, 0x2f}, {0x4000678990, 0x3, 0x3})
                /home/abokhanko/goroot/src/cmd/compile/internal/base/print.go:225 +0x200
            cmd/compile/internal/base.Fatalf(...)
                /home/abokhanko/goroot/src/cmd/compile/internal/base/print.go:194
            cmd/compile/internal/ssagen.(*ssafn).Fatalf(0x4000180008?, {0x1b3350?, 0x40?}, {0x9708a9, 0x29}, {0x40005590e0, 0x2, 0x40004f5488?})
                /home/abokhanko/goroot/src/cmd/compile/internal/ssagen/ssa.go:8208 +0x150
            cmd/compile/internal/ssa.(*Func).Fatalf(0x40004e7a00, {0x9708a9, 0x29}, {0x40005590e0, 0x2, 0x2})
                /home/abokhanko/goroot/src/cmd/compile/internal/ssa/func.go:741 +0x25c
            cmd/compile/internal/ssa.checkFunc(0x40004e7a00)
                /home/abokhanko/goroot/src/cmd/compile/internal/ssa/check.go:85 +0x6e0
            cmd/compile/internal/ssa.Compile(0x40004e7a00)
                /home/abokhanko/goroot/src/cmd/compile/internal/ssa/compile.go:67 +0x314
            cmd/compile/internal/ssagen.buildssa(0x40004eab40, 0x0)
                /home/abokhanko/goroot/src/cmd/compile/internal/ssagen/ssa.go:574 +0x1f80
            cmd/compile/internal/ssagen.Compile(0x40004eab40, 0x0)
                /home/abokhanko/goroot/src/cmd/compile/internal/ssagen/pgen.go:300 +0x30
            cmd/compile/internal/gc.compileFunctions.func5.1(0x4000180001?)
                /home/abokhanko/goroot/src/cmd/compile/internal/gc/compile.go:182 +0x3c
            cmd/compile/internal/gc.compileFunctions.func2(0x40005589c0?)
                /home/abokhanko/goroot/src/cmd/compile/internal/gc/compile.go:136 +0x28
            cmd/compile/internal/gc.compileFunctions.func5({0x4000562080, 0x5, 0x9890b8?})
                /home/abokhanko/goroot/src/cmd/compile/internal/gc/compile.go:181 +0x60
            cmd/compile/internal/gc.compileFunctions()
                /home/abokhanko/goroot/src/cmd/compile/internal/gc/compile.go:192 +0x1f4
            cmd/compile/internal/gc.Main(0x988f00)
                /home/abokhanko/goroot/src/cmd/compile/internal/gc/main.go:303 +0x1264
            main.main()
                /home/abokhanko/goroot/src/cmd/compile/main.go:57 +0x110


FAIL
FAIL    cmd/internal/testdir    0.455s
FAIL

What did you expect to see?

Test passes

[andreybokhanko]

The reason of the fail is incorrect SSA generated:

$ GOSSAFUNC=small6+ GOARM64=v8.1 ../bin/go test cmd/internal/testdir -run=Test/inline_sync.go
...
            compiling small6
            small6 func()
              b1:
                (?) v1 = InitMem <mem>
                (?) v2 = SP <uintptr> DEAD
                (?) v3 = SB <uintptr>
                (?) v4 = Addr <**sync.Mutex> {p.mutex} v3
                (33) v5 = Load <*sync.Mutex> v4 v1 (sync.m[*sync.Mutex])
                (+33) v6 = InlMark <void> [1] v1
                (83) v7 = NilCheck <*sync.Mutex> v5 v1
                (83) v8 = OffPtr <*int32> [0] v7
                (?) v9 = Const32 <int32> [0]
                (?) v10 = Const32 <int32> [1]
                (83) v11 = AtomicCompareAndSwap32Variant <bool,mem> v8 v9 v10 v1
                (83) v12 = Select1 <mem> v11
                (83) v13 = Select0 <uint32> v11
                If v13 -> b3 b2
              b2: <- b1
                (-90) v14 = Copy <*sync.Mutex> v5 (sync.m[*sync.Mutex])
                (-90) v15 = Copy <mem> v12
                (90) v16 = StaticLECall <mem> {AuxCall{sync.(*Mutex).lockSlow}} [8] v14 v15
                (90) v17 = SelectN <mem> [0] v16
                Plain -> b4
              b3: <- b1
                Plain -> b4
              b4: <- b3 b2
                (-34) v18 = Phi <mem> v12 v17
                (34) v19 = MakeResult <mem> v18
                Ret v19
            name sync.m[*sync.Mutex]: [v5 v14]

as can be seen, second Select instruction from this fragment:

                (83) v11 = AtomicCompareAndSwap32Variant <bool,mem> v8 v9 v10 v1
                (83) v12 = Select1 <mem> v11
                (83) v13 = Select0 <uint32> v11

is of wrong type -- uint32 instead of bool.

[andreybokhanko]

I have a fix ready for this; please assign this ticket on me.

[gopherbot]

Change https://go.dev/cl/583995 mentions this issue: cmd/compile: Fix SSA building bug for CAS atomics on ARM64