cmd/compile: PPC64.rules for Zero are not checking alignment

[rgdoliveira]

System information

Go version: 1.9
OS: Alpine Linux 3.6 (but it is not an Alpine specific issue)
Architecture: ppc64le

Seems that PPC64.rules for Zero are not checking alignment in the cases when they should be.
I reproduced this issue when tried to compile geth project and it failed with error:

compile: invalid offset for DS form load/store 00056 (/home/rdutra/repos/aports/community/geth/src/go-ethereum-1.7.0/build/_workspace/src/github.com/ethereum/go-ethereum/eth/downloader/statesync.go:452) MOVD R0, "".~r2+33(FP)

Steps to reproduce the behaviour

Clone go-ethereum repository in a ppc64le distribution
run make (with go 1.9 installed)

[ianlancetaylor]

CC @laboger

[gopherbot]

Change https://golang.org/cl/64970 mentions this issue: cmd/compile: fix regression in PPC64.rules move zero

[laboger]

When a MOVD instruction is used the offset field must be a multiple of 4. We had seen this problem a few months ago but MOVDstorezero did not get fixed at that time.

It can be reproduced when there is a function with something like this:

type Hash [32]byte

func testbool() (bool, Hash) {
        var h Hash
        return true, h 
}

When there is a MOVDstorezero to data that is >= 8 bytes but not nicely aligned, you can hit this error.

[laboger]

This should be backported to go 1.9.

[laboger]

I saw there was an announcement about go 1.9.1. Will this make it in there?

[ianlancetaylor]

I think 1.9.1 is going to be a security releases, so all the 1.9.1 issues will be bumped to 1.9.2.

[ianlancetaylor]

But I'll reopen this one now so that it is considered for 1.9.2.