micro-opt: replace stmGetEnclosingTRec() with a field access
[ghc-hetmet.git] / rts / Exception.cmm
index 43f53c7..6c887c2 100644 (file)
@@ -49,6 +49,8 @@ import ghczmprim_GHCziBool_True_closure;
 
    -------------------------------------------------------------------------- */
 
+STRING(stg_unblockAsync_err_str, "unblockAsyncExceptions#_ret")
+
 INFO_TABLE_RET( stg_unblockAsyncExceptionszh_ret, RET_SMALL )
 {
     CInt r;
@@ -81,6 +83,14 @@ INFO_TABLE_RET( stg_unblockAsyncExceptionszh_ret, RET_SMALL )
                 jump %ENTRY_CODE(Sp(0));
             }
         }
+        else {
+            /*
+               the thread might have been removed from the
+               blocked_exception list by someone else in the meantime.
+               Just restore the stack pointer and continue.  
+            */   
+            Sp_adj(2);
+        }
     }
 
     Sp_adj(1);
@@ -96,10 +106,10 @@ INFO_TABLE_RET( stg_blockAsyncExceptionszh_ret, RET_SMALL )
     jump %ENTRY_CODE(Sp(0));
 }
 
-blockAsyncExceptionszh_fast
+stg_blockAsyncExceptionszh
 {
     /* Args: R1 :: IO a */
-    STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, blockAsyncExceptionszh_fast);
+    STK_CHK_GEN( WDS(2)/* worst case */, R1_PTR, stg_blockAsyncExceptionszh);
 
     if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
        
@@ -119,25 +129,48 @@ blockAsyncExceptionszh_fast
     jump stg_ap_v_fast;
 }
 
-unblockAsyncExceptionszh_fast
+stg_unblockAsyncExceptionszh
 {
     CInt r;
 
     /* Args: R1 :: IO a */
-    STK_CHK_GEN( WDS(2), R1_PTR, unblockAsyncExceptionszh_fast);
+    STK_CHK_GEN( WDS(4), R1_PTR, stg_unblockAsyncExceptionszh);
+    /* 4 words: one for the unblock frame, 3 for setting up the
+     * stack to call maybePerformBlockedException() below.
+     */
 
+    /* If exceptions are already unblocked, there's nothing to do */
     if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
 
        StgTSO_flags(CurrentTSO) = StgTSO_flags(CurrentTSO) & 
           ~(TSO_BLOCKEX::I32|TSO_INTERRUPTIBLE::I32);
 
+       /* avoid growing the stack unnecessarily */
+       if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
+           Sp_adj(1);
+       } else {
+           Sp_adj(-1);
+           Sp(0) = stg_blockAsyncExceptionszh_ret_info;
+       }
+
         /* Eagerly raise a blocked exception, if there is one */
         if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
             /* 
              * We have to be very careful here, as in killThread#, since
              * we are about to raise an async exception in the current
              * thread, which might result in the thread being killed.
+             *
+             * Now, if we are to raise an exception in the current
+             * thread, there might be an update frame above us on the
+             * stack due to unsafePerformIO.  Hence, the stack must
+             * make sense, because it is about to be snapshotted into
+             * an AP_STACK.
              */
+            Sp_adj(-3);
+            Sp(2) = stg_ap_v_info;
+            Sp(1) = R1;
+            Sp(0) = stg_enter_info;
+
             SAVE_THREAD_STATE();
             (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr", 
                                                      CurrentTSO "ptr") [R1];
@@ -150,23 +183,19 @@ unblockAsyncExceptionszh_fast
                    ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
                    jump %ENTRY_CODE(Sp(0));
                }
+            } else {
+                /* we'll just call R1 directly, below */
+                Sp_adj(3);
             }
         }
 
-       /* avoid growing the stack unnecessarily */
-       if (Sp(0) == stg_unblockAsyncExceptionszh_ret_info) {
-           Sp_adj(1);
-       } else {
-           Sp_adj(-1);
-           Sp(0) = stg_blockAsyncExceptionszh_ret_info;
-       }
     }
     TICK_UNKNOWN_CALL();
     TICK_SLOW_CALL_v();
     jump stg_ap_v_fast;
 }
 
-asyncExceptionsBlockedzh_fast
+stg_asyncExceptionsBlockedzh
 {
     /* args: none */
     if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {
@@ -176,7 +205,7 @@ asyncExceptionsBlockedzh_fast
     }
 }
 
-killThreadzh_fast
+stg_killThreadzh
 {
     /* args: R1 = TSO to kill, R2 = Exception */
 
@@ -187,7 +216,8 @@ killThreadzh_fast
     target = R1;
     exception = R2;
     
-    STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, killThreadzh_fast);
+    /* Needs 3 words because throwToSingleThreaded uses some stack */
+    STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, stg_killThreadzh);
 
     /* 
      * We might have killed ourselves.  In which case, better be *very*
@@ -201,6 +231,14 @@ killThreadzh_fast
         goto loop;
     }
     if (target == CurrentTSO) {
+        /*
+         * So what should happen if a thread calls "throwTo self" inside
+         * unsafePerformIO, and later the closure is evaluated by another
+         * thread?  Presumably it should behave as if throwTo just returned,
+         * and then continue from there.  See #3279, #3288.  This is what
+         * happens: on resumption, we will just jump to the next frame on
+         * the stack, which is the return point for stg_killThreadzh.
+         */
        SAVE_THREAD_STATE();
        /* ToDo: what if the current thread is blocking exceptions? */
        foreign "C" throwToSingleThreaded(MyCapability() "ptr", 
@@ -215,8 +253,8 @@ killThreadzh_fast
     } else {
        W_ out;
        W_ retcode;
-       out = BaseReg + OFFSET_StgRegTable_rmp_tmp_w;
-       
+       out = Sp - WDS(1); /* ok to re-use stack space here */
+
        (retcode) = foreign "C" throwTo(MyCapability() "ptr",
                                      CurrentTSO "ptr",
                                      target "ptr",
@@ -273,13 +311,13 @@ INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
 {
   R2 = StgClosure_payload(R1,1); /* h */
   R1 = StgClosure_payload(R1,0); /* x */
-  jump catchzh_fast;
+  jump stg_catchzh;
 }
 
-catchzh_fast
+stg_catchzh
 {
     /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
-    STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, catchzh_fast);
+    STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, stg_catchzh);
   
     /* Set up the catch frame */
     Sp = Sp - SIZEOF_StgCatchFrame;
@@ -302,13 +340,13 @@ catchzh_fast
  *
  *   raise = {err} \n {} -> raise#{err}
  *
- * It is used in raisezh_fast to update thunks on the update list
+ * It is used in stg_raisezh to update thunks on the update list
  * -------------------------------------------------------------------------- */
 
 INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
 {
   R1 = StgThunk_payload(R1,0);
-  jump raisezh_fast;
+  jump stg_raisezh;
 }
 
 section "data" {
@@ -320,10 +358,10 @@ INFO_TABLE_RET(stg_raise_ret, RET_SMALL, P_ arg1)
   R1 = Sp(1);
   Sp = Sp + WDS(2);
   W_[no_break_on_exception] = 1;  
-  jump raisezh_fast;
+  jump stg_raisezh;
 }
 
-raisezh_fast
+stg_raisezh
 {
     W_ handler;
     W_ frame_type;
@@ -360,7 +398,7 @@ retry_pop_stack:
       W_ r;
       trec = StgTSO_trec(CurrentTSO);
       (r) = foreign "C" stmValidateNestOfTransactions(trec "ptr") [];
-      ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
+      outer  = StgTRecHeader_enclosing_trec(trec);
       foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
       foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
 
@@ -400,7 +438,7 @@ retry_pop_stack:
             // deadlock if an exception is raised in InteractiveUI,
             // for exmplae.  Perhaps the stop_on_exception flag should
             // be per-thread.
-            W_[rts_stop_on_exception] = 0;
+            CInt[rts_stop_on_exception] = 0;
             ("ptr" ioAction) = foreign "C" deRefStablePtr (W_[rts_breakpoint_io_action] "ptr") [];
             Sp = Sp - WDS(7);
             Sp(6) = exception;
@@ -460,7 +498,7 @@ retry_pop_stack:
     } else {
       W_ trec, outer;
       trec = StgTSO_trec(CurrentTSO);
-      ("ptr" outer) = foreign "C" stmGetEnclosingTRec(trec "ptr") [];
+      outer  = StgTRecHeader_enclosing_trec(trec);
       foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
       foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
       StgTSO_trec(CurrentTSO) = outer;
@@ -484,8 +522,8 @@ retry_pop_stack:
     jump RET_LBL(stg_ap_pv);
 }
 
-raiseIOzh_fast
+stg_raiseIOzh
 {
   /* Args :: R1 :: Exception */
-  jump raisezh_fast;
+  jump stg_raisezh;
 }