cmd/compile: ice for out of range for uint

[lmaltsis]

Go version

go version go1.27-devel_8594bf4621

Output of go env in your module/workspace:

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='/research/compilers/gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/user/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build691699402=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/home/user/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/user/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/user/software/go/slot-a/src'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/user/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/user/software/go/slot-a/src/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.27-devel_8594bf4621 Fri May 1 17:19:05 2026 -0700'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

https://go.dev/play/p/kb2Kb0El9PP

$ cat /tmp/bug.go
package main

import "fmt"

func main() {
        v1 := 0
        fmt.Println(0 >> ((2 ^ 0xffffffffffffffff<<2) >> v1))
}

$ go build /tmp/bug.go

What did you see happen?

# command-line-arguments
/tmp/bug.go:7:13: internal compiler error: 73786976294838206462 out of range for uint

goroutine 407 [running]:
runtime/debug.Stack()
        /home/user/software/go/slot-a/src/src/runtime/debug/stack.go:26 +0x5e
cmd/compile/internal/base.FatalfAt({0x19640a0?, 0x0?}, {0xfbb277, 0x16}, {0x289201a288f8, 0x2, 0x2})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/base/print.go:232 +0x18b
cmd/compile/internal/base.Fatalf(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/base/print.go:197
cmd/compile/internal/ir.IntVal(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ir/val.go:33
cmd/compile/internal/ssagen.(*state).exprCheckPtr(0x289201a02000, {0x19678f0, 0x2892017ef900}, 0x1)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3101 +0x6a3d
cmd/compile/internal/ssagen.(*state).expr(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3031
cmd/compile/internal/ssagen.(*state).exprCheckPtr(0x289201a02000, {0x1966888, 0x28920188a360}, 0x1)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3399 +0x404b
cmd/compile/internal/ssagen.(*state).expr(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3031
cmd/compile/internal/ssagen.(*state).exprCheckPtr(0x289201a02000, {0x1966888, 0x28920188a3c0}, 0x1)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3400 +0x4075
cmd/compile/internal/ssagen.(*state).expr(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3031
cmd/compile/internal/ssagen.(*state).exprCheckPtr(0x289201a02000, {0x1965c08, 0x289201962600}, 0x1)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3230 +0x1870
cmd/compile/internal/ssagen.(*state).expr(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3031
cmd/compile/internal/ssagen.(*state).putArg(0x289201a02000, {0x1965c08, 0x289201962600}, 0x2892014b6720)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:5750 +0x4b
cmd/compile/internal/ssagen.(*state).call(0x289201a02000, 0x289201964140, 0x0, 0x0, {0x0, 0x0})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:5112 +0x153e
cmd/compile/internal/ssagen.(*state).callResult(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:4957
cmd/compile/internal/ssagen.(*state).exprCheckPtr(0x289201a02000, {0x1965e60, 0x289201964140}, 0x1)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3709 +0x174d
cmd/compile/internal/ssagen.(*state).expr(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:3031
cmd/compile/internal/ssagen.(*state).stmt(0x289201a02000, {0x19672b0, 0x28920195e4b0})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1919 +0x69ab
cmd/compile/internal/ssagen.(*state).stmtList(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1654
cmd/compile/internal/ssagen.(*state).stmt(0x289201a02000, {0x19672b0, 0x28920195e460})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1679 +0x2a5
cmd/compile/internal/ssagen.(*state).stmtList(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1654
cmd/compile/internal/ssagen.(*state).stmt(0x289201a02000, {0x1966e00, 0x289201950e80})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1684 +0x6465
cmd/compile/internal/ssagen.(*state).stmtList(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1654
cmd/compile/internal/ssagen.(*state).stmt(0x289201a02000, {0x1966e00, 0x289201951000})
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1684 +0x6465
cmd/compile/internal/ssagen.(*state).stmtList(...)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:1654
cmd/compile/internal/ssagen.buildssa(0x28920177b040, 0xbb, 0x0)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/ssa.go:576 +0x2bb4
cmd/compile/internal/ssagen.Compile(0x28920177b040, 0xbb, 0x0?)
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/ssagen/pgen.go:304 +0x88
cmd/compile/internal/gc.compileFunctions.func2()
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/gc/compile.go:177 +0x85
created by cmd/compile/internal/gc.compileFunctions in goroutine 1
        /home/user/software/go/slot-a/src/src/cmd/compile/internal/gc/compile.go:163 +0xd9

What did you expect to see?

Either frontend error like this triggers

package main

import "fmt"

func main() {
	fmt.Println(0 >> ((2 ^ 0xffffffffffffffff<<2) >> 0))
}

./prog.go:6:19: ((2 ^ 0xffffffffffffffff << 2) >> 0) (untyped int constant 73786976294838206462) overflows uint

or successful compilation with overflow at runtime

[lmaltsis]

Also triggers on 1.25 and 1.26 on go.dev/play

[cuonglm]

git bisect points to CL 465096.

However, this seems to be a problem with types2, since it should report this error instead.

cc @griesemer @mrkfrmn

[gabyhelp]

Related Issues

• cmd/compile: internal compiler error: unexpected type uint for 1 #32959 (closed)
• cmd/compile: out of range integer in range loop crashes the compiler #65133 (closed)
• cmd/compile: internal compiler error: panic: builtins.go: assertion failed #61486 (closed)
• cmd/compile: ice expecting positive value on loop iterating by math.MinInt64 (regression) #78641 (closed)
• cmd/compile: internal compiler error: unhandled OCONV ARRAY -> UINT8 #52020 (closed)
• gccgo: internal compiler error in do_get_backend on valid program of shifting negative integer by variable #78471
• cmd/compile: incorrectly reports `x - minimumValue` overflows for integers #68628 (closed)
• cmd/compile: ICE when using unsafe.Sizeof on generic type #77382 (closed)
• cmd/compile/internal/SSA: panic in Compile on linux-amd64-noopt #54906 (closed)
• cmd/compile: internal compiler error: unhandled OCONV INT -> COMPLEX128 #50193 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[griesemer]

Reproducer without fmt.Println:

package p
func f() {
	s := 0
	_ = 0 >> (0xffffffffffffffff << 2 >> s)
}

passes types2 but leads to an ICE.

package p
func f() {
	_ = 0 >> (0xffffffffffffffff << 2 >> 0)
}

leads to a type checker error:

testdata/manual.go:11:11: (0xffffffffffffffff << 2 >> 0) (untyped int constant 73786976294838206460) overflows uint

[griesemer]

Marked for 1.27 in case we get to it before RC1.
Ok to push to 1.28 since this has been around for a long time (even before 1.25).

[cuonglm]

Marked for 1.27 in case we get to it before RC1. Ok to push to 1.28 since this has been around for a long time (even before 1.25).

I believe this started since go1.19 release.

package main

var v1 = 0

func main() {
	_ = 0 >> ((2 ^ 0xffffffffffffffff<<2) >> v1)
}

# go1.18 with old typecheck
$ go1.18.10 tool compile -G=0 main.go
main.go:6:8: constant 73786976294838206462 overflows uint

# go1.18 with types2
$ go1.18.10 tool compile -G=1 main.go
main.go:6:12: (2 ^ 0xffffffffffffffff << 2) (untyped int constant 73786976294838206462) overflows uint
main.go:6:13: 2 ^ 0xffffffffffffffff << 2 (untyped int constant 73786976294838206462) overflows uint

# go1.19 with types2 as the sole typechecker silences the overflow, only reported by typecheck
$ go1.19.13 tool compile main.go     
main.go:6:40: constant 73786976294838206462 overflows uint

[griesemer]

Related to #77117.

[griesemer]

Has been around for a while and somewhat esoteric. Also, tricky to fix and get right.
Ok to move to 1.28.