RTS: implement sleep primitives

Note that an alternative implementation choice is just to implement
them as SAIL functions manipulating a global variable.
Not sure which is better.

2 files changed, 29 insertions, 5 deletions

diff --git a/lib/rts.c b/lib/rts.c
index ebfa7c6d..f5426814 100644
--- a/lib/rts.c
+++ b/lib/rts.c
@@ -25,12 +25,27 @@ unit sail_exit(unit u)
   return UNIT;
 }
 
+bool g_sleeping = false;
+
 unit sleep_request(const unit u)
 {
-  fprintf(stderr, "Sail model going to sleep\n");
+  fprintf(stderr, "Sail CPU model going to sleep\n");
+  g_sleeping = true;
+  return UNIT;
+}
+
+unit wakeup_request(const unit u)
+{
+  fprintf(stderr, "Sail CPU model waking up\n");
+  g_sleeping = false;
   return UNIT;
 }
 
+bool sleeping(const unit u)
+{
+    return g_sleeping;
+}
+
 /* ***** Sail memory builtins ***** */
 
 /*
@@ -448,7 +463,6 @@ int process_arguments(int argc, char *argv[])
       g_elf_entry = elf_entry;
   }
 
-  fprintf(stderr, "Parsed all command line options\n");
   return 0;
 }
 
diff --git a/lib/rts.h b/lib/rts.h
index b0e59252..78387ab4 100644
--- a/lib/rts.h
+++ b/lib/rts.h
@@ -21,12 +21,22 @@ unit sail_assert(bool b, sail_string msg);
 unit sail_exit(unit);
 
 /*
- * ASL->Sail model has an EnterLowPowerState() function that calls a
- * sleep request builtin. If it gets called we print a message and
- * exit the model.
+ * Put processor to sleep until an external device calls wakeup_request().
  */
 unit sleep_request(const unit u);
 
+/*
+ * Stop processor sleeping.
+ * (Typically called when a device generates an interrupt.)
+ */
+unit wakeup_request(const unit u);
+
+/*
+ * Test whether processor is sleeping.
+ * (Typically used to disable execution of instructions.)
+ */
+bool sleeping(const unit u);
+
 /* ***** Memory builtins ***** */
 
 void write_mem(uint64_t, uint64_t);