if !*flags.SymABIs {
		buf.WriteString(objabi.HeaderString())
		fmt.Fprintf(buf, "!\n")
	}

	// Set macros for GOEXPERIMENTs so we can easily switch
	// runtime assembly code based on them.
	if objabi.LookupPkgSpecial(ctxt.Pkgpath).AllowAsmABI {
		for _, exp := range buildcfg.Experiment.Enabled() {
			flags.D = append(flags.D, "GOEXPERIMENT_"+exp)
		}
	}

	var ok, diag bool
	var failedFile string