internal/cpu: inline DebugOptions

internal/cpu.DebugOptions is only ever set in runtime.cpuinit on
unix-like platforms. DebugOptions itself is only used in
MustHaveDebugOptionsSupport, so inline the GOOS check there.

Change-Id: I6a35d6b8afcdadfc59585258002f53c20026116c
Reviewed-on: https://go-review.googlesource.com/c/go/+/699775
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Tobias Klauser <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Florian Lehner <[email protected]>

Author: tklauser

src/internal/cpu/cpu.go

@@ -8,11 +8,6 @@ package cpu
 
 import _ "unsafe" // for linkname
 
-// DebugOptions is set to true by the runtime if the OS supports reading
-// GODEBUG early in runtime startup.
-// This should not be changed after it is initialized.
-var DebugOptions bool
-
 // CacheLinePad is used to pad structs to avoid false sharing.
 type CacheLinePad struct{ _ [CacheLinePadSize]byte }
 

src/internal/cpu/cpu_test.go

@@ -9,11 +9,14 @@ import (
 	"internal/godebug"
 	"internal/testenv"
 	"os/exec"
+	"runtime"
 	"testing"
 )
 
 func MustHaveDebugOptionsSupport(t *testing.T) {
-	if !DebugOptions {
+	switch runtime.GOOS {
+	case "aix", "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd", "illumos", "solaris", "linux":
+	default:
 		t.Skipf("skipping test: cpu feature options not supported by OS")
 	}
 }

src/runtime/proc.go

@@ -760,10 +760,6 @@ const (
 // cpuinit sets up CPU feature flags and calls internal/cpu.Initialize. env should be the complete
 // value of the GODEBUG environment variable.
 func cpuinit(env string) {
-	switch GOOS {
-	case "aix", "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd", "illumos", "solaris", "linux":
-		cpu.DebugOptions = true
-	}
 	cpu.Initialize(env)
 
 	// Support cpu feature variables are used in code generated by the compiler