runtime: drop haveexperiment, sys.GOEXPERIMENT

We have ways to statically access experiments now, so we don't need a
relatively clunky string-parsing dynamic way to do it.

Change-Id: I5d75480916eef4bde2c30d5fe30593180da77ff2
Reviewed-on: https://go-review.googlesource.com/c/go/+/307815
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/internal/objabi/util.go

@@ -171,7 +171,6 @@ func init() {
 	}
 
 	// Set GOEXPERIMENT to the parsed and canonicalized set of experiments.
-	// This format must be parseable by runtime.haveexperiment.
 	GOEXPERIMENT = expList()
 }
 

src/cmd/link/internal/ld/main.go

@@ -118,8 +118,6 @@ func Main(arch *sys.Arch, theArch Arch) {
 	addstrdata1(ctxt, "runtime.defaultGOROOT="+final)
 	addstrdata1(ctxt, "cmd/internal/objabi.defaultGOROOT="+final)
 
-	addstrdata1(ctxt, "runtime/internal/sys.GOEXPERIMENT="+objabi.GOEXPERIMENT)
-
 	// TODO(matloob): define these above and then check flag values here
 	if ctxt.Arch.Family == sys.AMD64 && objabi.GOOS == "plan9" {
 		flag.BoolVar(&flag8, "8", false, "use 64-bit addresses in symbol table")

src/runtime/heapdump.go

@@ -532,7 +532,7 @@ func dumpparams() {
 	dumpint(uint64(arenaStart))
 	dumpint(uint64(arenaEnd))
 	dumpstr(sys.GOARCH)
-	dumpstr(sys.GOEXPERIMENT)
+	dumpstr(buildVersion)
 	dumpint(uint64(ncpu))
 }
 

src/runtime/internal/sys/arch.go

@@ -52,5 +52,3 @@ const MinFrameSize = _MinFrameSize
 // StackAlign is the required alignment of the SP register.
 // The stack must be at least word aligned, but some architectures require more.
 const StackAlign = _StackAlign
-
-var GOEXPERIMENT string // set by cmd/link

src/runtime/proc.go

@@ -5,7 +5,6 @@
 package runtime
 
 import (
-	"internal/bytealg"
 	"internal/cpu"
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
@@ -6039,26 +6038,6 @@ func setMaxThreads(in int) (out int) {
 	return
 }
 
-func haveexperiment(name string) bool {
-	// GOEXPERIMENT is a comma-separated list of enabled
-	// experiments. It's not the raw environment variable, but a
-	// pre-processed list from cmd/internal/objabi.
-	x := sys.GOEXPERIMENT
-	for x != "" {
-		xname := ""
-		i := bytealg.IndexByteString(x, ',')
-		if i < 0 {
-			xname, x = x, ""
-		} else {
-			xname, x = x[:i], x[i+1:]
-		}
-		if xname == name {
-			return true
-		}
-	}
-	return false
-}
-
 //go:nosplit
 func procPin() int {
 	_g_ := getg()