runtime: integer divide by zero check doesn't work on ARM

[gopherbot]

by capnm9:

hg id
166d946fa77f tip

This is a regression from go1.1.1.

func main() {
    a := 0
    b := 1 / a
    _ = b
}

uname -a
Linux rpi 3.6.11+ #474 PREEMPT Thu Jun 13 17:14:42 BST 2013 armv6l GNU/Linux

GOTRACEBACK=2; go run main.go 
runtime: unknown pc 0x1 at frame 11
fatal error: invalid stack

goroutine 1 [garbage collection]:
runtime.gc(0x0)
    /d/go/src/pkg/runtime/mgc0.c:2019 +0x1cc fp=0xb6eb5ecc
runtime.mallocgc(0x8, 0x0, 0x1, 0x1)
    /d/go/src/pkg/runtime/zmalloc_linux_arm.c:103 +0x1d4 fp=0xb6eb5f00
runtime.mal(0x8)
    /d/go/src/pkg/runtime/zmalloc_linux_arm.c:665 +0x40 fp=0xb6eb5f14
copyin(0x2da28, 0xb6eb5f54, 0xb6eb5f60)
    /d/go/src/pkg/runtime/iface.c:152 +0x64 fp=0xb6eb5f30
runtime.convT2E(0x2da28, 0x520c0, 0x16, 0x2da28, 0x16, ...)
    /d/go/src/pkg/runtime/iface.c:220 +0x44 fp=0xb6eb5f4c
runtime.newErrorString(0x520c0, 0x16, 0xb6eb5f7c)
    /d/go/src/pkg/runtime/error.go:74 +0x3c fp=0xb6eb5f64
runtime.panicstring(0x520c0)
    /d/go/src/pkg/runtime/panic.c:489 +0x7c fp=0xb6eb5f84
runtime.panicdivide()
    /d/go/src/pkg/runtime/vlrt_arm.c:40 +0x2c fp=0xb6eb5f8c
udiv(0x1)
    /d/go/src/pkg/runtime/vlop_arm.s:139 +0x9c fp=0xb6eb5f8c
main.main()
    /tmp/main.go:7 +0x38 fp=0xb6eb5f90
main.main()
    /tmp/main.go:7 +0x38 fp=0xb6eb5f94

goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
    /d/go/src/pkg/runtime/mheap.c:438
runtime.goexit()
    /d/go/src/pkg/runtime/proc.c:1269
created by runtime.main
    /d/go/src/pkg/runtime/proc.c:165
exit status 2

----

/d/go1.1.1/bin/go run main.go 
panic: runtime error: integer divide by zero

goroutine 1 [running]:
runtime.panic(0x336e8, 0x10100008)
    /d/go1.1.1/src/pkg/runtime/panic.c:247 +0x128
runtime.panicstring(0x47088)
    /d/go1.1.1/src/pkg/runtime/panic.c:487 +0x8c
runtime.panicdivide()
    /d/go1.1.1/src/pkg/runtime/vlrt_arm.c:40 +0x28
udiv()
    /d/go1.1.1/src/pkg/runtime/vlop_arm.s:139 +0x9c
main.main()
    /tmp/main.go:7 +0x34

goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
    /d/go1.1.1/src/pkg/runtime/mheap.c:421
runtime.goexit()
    /d/go1.1.1/src/pkg/runtime/proc.c:1223
created by runtime.main
    /d/go1.1.1/src/pkg/runtime/proc.c:165
exit status 2

----

uname -a
Linux t2t 3.8.0-23-generic #34-Ubuntu SMP Wed May 29 20:22:58 UTC 2013 x86_64 x86_64
x86_64 GNU/Linux

GOTRACEBACK=1; go run main.go 
panic: runtime error: integer divide by zero
[signal 0x8 code=0x1 addr=0x400c12 pc=0x400c12]

goroutine 1 [running]:
main.main()
    /tmp/main.go:7 +0x12

goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
    /d/go/src/pkg/runtime/mheap.c:438
runtime.goexit()
    /d/go/src/pkg/runtime/proc.c:1269
created by runtime.main
    /d/go/src/pkg/runtime/proc.c:165
exit status 2

[robpike]

Comment 1:

Labels changed: added priority-soon, compilerbug, arch-arm, removed priority-triage.

Status changed to Accepted.

[robpike]

Comment 2:

Labels changed: removed compilerbug.

[rsc]

Comment 3:

Labels changed: added go1.2.

[rsc]

Comment 4:

I think this is already fixed. I have added a test to the tree to find out.

Status changed to Started.

[ceh]

Comment 5:

Still broken for me.
$ uname -a
Linux nsa310 3.5.1 #1 Mon Sep 24 19:17:28 CEST 2012 armv5tel GNU/Linux
$ go version
go version devel +77a4d225cc7e Wed Sep 11 10:50:56 2013 +1000 linux/arm
$ cat issue5805.go
package main
func main() {
        a := 0
        b := 1 / a
        _ = b
}
$ go run issue5805.go
runtime: unknown argument frame size for udiv called from 0x10c38 [main.main]
fatal error: invalid stack
goroutine 1 [garbage collection]:
runtime.gc(0x0)
        /home/ceh/src/go/src/pkg/runtime/mgc0.c:2020 +0x1a0 fp=0xb6f37eac
runtime.mallocgc(0x8, 0x0, 0x0)
        /home/ceh/src/go/src/pkg/runtime/malloc.goc:143 +0x210 fp=0xb6f37ee8
runtime.mal(0x8)
        /home/ceh/src/go/src/pkg/runtime/malloc.goc:700 +0x38 fp=0xb6f37ef8
copyin(0x37150, 0xb6f37f38, 0xb6f37f44)
        /home/ceh/src/go/src/pkg/runtime/iface.c:153 +0x6c fp=0xb6f37f14
runtime.convT2E(0x37150, 0x64368, 0x16, 0x37150, 0x16)
        /home/ceh/src/go/src/pkg/runtime/iface.c:221 +0x44 fp=0xb6f37f30
runtime.newErrorString(0x64368, 0x16, 0xb6f37f60)
        /home/ceh/src/go/src/pkg/runtime/error.go:74 +0x3c fp=0xb6f37f48
runtime.panicstring(0x64368)
        /home/ceh/src/go/src/pkg/runtime/panic.c:519 +0x84 fp=0xb6f37f68
runtime.panicdivide()
        /home/ceh/src/go/src/pkg/runtime/vlrt_arm.c:42 +0x2c fp=0xb6f37f70
runtime: unknown argument frame size for udiv called from 0x10c38 [main.main]
udiv()
        /home/ceh/src/go/src/pkg/runtime/vlop_arm.s:171 +0x9c fp=0xb6f37f70
main.main()
        /home/ceh/src/issue5805.go:5 +0x38 fp=0xb6f37f7c
runtime: unexpected return pc for main.main called from 0x0
main.main()
        /home/ceh/src/issue5805.go:5 +0x38 fp=0xb6f37f88
goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
        /home/ceh/src/go/src/pkg/runtime/mheap.c:439
runtime.goexit()
        /home/ceh/src/go/src/pkg/runtime/proc.c:1386
exit status 2

[rsc]

Comment 6:

This is a bit subtle to fix. udiv really needs to be changed not to depend quite so much
on the 5l code layout. I will do that for Go 1.2 but perhaps not for the first release
candidate. It will require writing some better divide tests.

[rsc]

Comment 7:

This issue was closed by revision b2794a1c2ed8c74563cf28d9e4a9b3f1db43ef1.

Status changed to Fixed.

[gopherbot]

Comment 8:

CL https://golang.org/cl/13632048 references this issue.

[gopherbot]

Comment 9:

CL https://golang.org/cl/13632048 references this issue.