As far as I understand, it's only about including more information in the compilers json output. But that information was already available in non-json output

As far as I understand, it's only about including more information in the compilers json output. But that information was already available in non-json output in previos Go versions. To get explanations on the optimization decisions by the compiler build your package with: go build -gcflags="-m -m" See also: go tool compile -h go doc cmd/compile