What steps will reproduce the problem?

$ cd src/pkg/crypto/md5
$ go vet                    

What is the expected output?

Nothing as this is valid assembler

$ grep TEXT md5block_amd64.s
TEXT    ·block(SB),NOSPLIT,$0-32

What do you see instead?

: md5block_amd64.s:16: [amd64] wrong argument size 0; expected $...-32

If you replace the TEXT line with

TEXT    ·block(SB),7,$0-32

Then go vet ceases to complain, probably indicating it doesn't understand the NOSPLIT
#define

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

linux/amd64

Which version are you using?  (run 'go version')

go version devel +746466b52725 Wed Oct 30 08:54:53 2013 -0700 linux/amd64

Please provide any additional information below.

Fresh version of go tools fetched with

go get code.google.com/p/go.tools/cmd/vet

src/code.google.com/p/go.tools$ hg summary
parent: 410:60eb0bc2b915 tip
 go.tools: clear DeclarationErrors flag; it's redundant w.r.t go/types checking.
branch: default
commit: (clean)
update: (current)