cpu: rename the misleading inSyscall to noSquashFromTC

isSyscall was originally created because during handling of a syscall in SE
mode the threadcontext had to be updated. However, in many places this is used
in FS mode (e.g. fault handlers) and the name doesn't make much sense. The
boolean actually stops gem5 from squashing speculative and non-committed state
when a write to a threadcontext happens, so re-name the variable to something
more appropriate

1 files changed, 9 insertions, 4 deletions

diff --git a/src/cpu/o3/thread_state.hh b/src/cpu/o3/thread_state.hh
index 9273b00da..96ccfc95c 100644
--- a/src/cpu/o3/thread_state.hh
+++ b/src/cpu/o3/thread_state.hh
@@ -61,10 +61,15 @@ struct O3ThreadState : public ThreadState {
     /** Pointer to the CPU. */
     O3CPU *cpu;
   public:
-    /** Whether or not the thread is currently in syscall mode, and
-     * thus able to be externally updated without squashing.
+    /* This variable controls if writes to a thread context should cause a all
+     * dynamic/speculative state to be thrown away. Nominally this is the
+     * desired behavior because the external thread context write has updated
+     * some state that could be used by an inflight instruction, however there
+     * are some cases like in a fault/trap handler where this behavior would
+     * lead to successive restarts and forward progress couldn't be made. This
+     * variable controls if the squashing will occur.
      */
-    bool inSyscall;
+    bool noSquashFromTC;
 
     /** Whether or not the thread is currently waiting on a trap, and
      * thus able to be externally updated without squashing.
@@ -73,7 +78,7 @@ struct O3ThreadState : public ThreadState {
 
     O3ThreadState(O3CPU *_cpu, int _thread_num, Process *_process)
         : ThreadState(_cpu, _thread_num, _process),
-          cpu(_cpu), inSyscall(0), trapPending(0)
+          cpu(_cpu), noSquashFromTC(false), trapPending(false)
     {
         if (!FullSystem)
             return;