Make Process.clock_gettime(Process::CLOCK_MONOTONIC) simpler

Author: chrisseaton

src/main/java/org/truffleruby/core/ProcessNodes.java

@@ -27,7 +27,6 @@ public abstract class ProcessNodes {
     @Primitive(name = "process_time_nanotime")
     public abstract static class ProcessTimeNanoTimeNode extends PrimitiveArrayArgumentsNode {
 
-        @TruffleBoundary
         @Specialization
         protected long nanoTime() {
             return System.nanoTime();

src/main/ruby/truffleruby/core/process.rb

@@ -156,10 +156,10 @@ def self.clock_gettime(id, unit=:float_second)
     end
 
     case id
-    when CLOCK_REALTIME
-      time = Primitive.process_time_instant
     when CLOCK_MONOTONIC
       time = Primitive.process_time_nanotime
+    when CLOCK_REALTIME
+      time = Primitive.process_time_instant
     else
       time = Truffle::POSIX.truffleposix_clock_gettime(id)
       Errno.handle if time == 0
@@ -170,20 +170,20 @@ def self.clock_gettime(id, unit=:float_second)
 
   def self.nanoseconds_to_unit(nanoseconds, unit)
     case unit
-    when :nanosecond
-      nanoseconds
-    when :microsecond
-      nanoseconds / 1_000
-    when :millisecond
-      nanoseconds / 1_000_000
-    when :second
-      nanoseconds / 1_000_000_000
+    when :float_second, nil
+      nanoseconds / 1e9
     when :float_microsecond
       nanoseconds / 1e3
     when :float_millisecond
       nanoseconds / 1e6
-    when :float_second, nil
-      nanoseconds / 1e9
+    when :second
+      nanoseconds / 1_000_000_000
+    when :millisecond
+      nanoseconds / 1_000_000
+    when :microsecond
+      nanoseconds / 1_000
+    when :nanosecond
+      nanoseconds
     else
       raise ArgumentError, "unexpected unit: #{unit}"
     end