cmd/compile: ssacheck failure on GOARCH=arm building runtime

[rsc]

Discovered by accident. I can provoke an ssacheck failure on arm reliably with:

$ VM=$(gomote create linux-arm)
$ gomote push $VM
$ gomote run $VM go/src/make.bash
$ gomote run $VM go/bin/go build -a -gcflags=-d=ssa/check/on -v runtme
runtime/internal/sys
runtime/internal/atomic
runtime
# runtime
../src/runtime/malloc.go:892:14: internal compiler error: bad int32 AuxInt value for v54

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/tmp/workdir/go/src/runtime/debug/stack.go:24 +0x80
cmd/compile/internal/gc.Fatalf(0x6dc821, 0x1d, 0x121ba4d0, 0x1, 0x1)
	/tmp/workdir/go/src/cmd/compile/internal/gc/subr.go:182 +0x1c0
cmd/compile/internal/gc.(*ssafn).Fatalf(0x113ef140, 0x26, 0x37c0e, 0x6dc821, 0x1d, 0x121ba4d0, 0x1, 0x1)
	/tmp/workdir/go/src/cmd/compile/internal/gc/ssa.go:5176 +0x54
cmd/compile/internal/ssa.(*Func).Fatalf(0x12ffe1e0, 0x6dc821, 0x1d, 0x121ba4d0, 0x1, 0x1)
	/tmp/workdir/go/src/cmd/compile/internal/ssa/func.go:497 +0x64
cmd/compile/internal/ssa.checkFunc(0x12ffe1e0)
	/tmp/workdir/go/src/cmd/compile/internal/ssa/check.go:140 +0x1508
cmd/compile/internal/ssa.Compile(0x12ffe1e0)
	/tmp/workdir/go/src/cmd/compile/internal/ssa/compile.go:110 +0x31c
cmd/compile/internal/gc.buildssa(0x1161f520, 0x0, 0x0)
	/tmp/workdir/go/src/cmd/compile/internal/gc/ssa.go:216 +0xb28
cmd/compile/internal/gc.compileSSA(0x1161f520, 0x0)
	/tmp/workdir/go/src/cmd/compile/internal/gc/pgen.go:238 +0x24
cmd/compile/internal/gc.compile(0x1161f520)
	/tmp/workdir/go/src/cmd/compile/internal/gc/pgen.go:217 +0x208
cmd/compile/internal/gc.funccompile(0x1161f520)
	/tmp/workdir/go/src/cmd/compile/internal/gc/dcl.go:1036 +0xa4
cmd/compile/internal/gc.Main(0x6eb0a0)
	/tmp/workdir/go/src/cmd/compile/internal/gc/main.go:618 +0x25c8
main.main()
	/tmp/workdir/go/src/cmd/compile/main.go:49 +0x7c

Error running run: exit status 2
$ 

I thought maybe the problem was 32-bit-specific, but it does not happen if I build with GOARCH=386 ./make.bash on my Mac, so maybe it is only arm-specific.

I don't know what this means, really, but I thought you'd want to see it.

/cc @randall77 @dr2chase @cherrymui

[cherrymui]

It is ARM specific. ssacheck complains a BICconst's AuxInt does not fit into int32. It fits into uint32 so the generated code is not affected. I'll have a CL soon.

[gopherbot]

Change https://golang.org/cl/74770 mentions this issue: cmd/compile: on ARM, make sure *const's AuxInt fit into int32

[cherrymui]

Seems this also happens with Go 1.9. Are we going to fix Go 1.9?

[randall77]

If the generated code is correct, and this only affects the ssacheck builder, I don't see a reason to backport to 1.9.

[gopherbot]

Change https://golang.org/cl/76024 mentions this issue: cmd/compile: enable ssacheck for tests in ssa_test.go