[project @ 2003-01-10 16:33:49 by simonmar]

[ghc-hetmet.git] / ghc / rts / Interpreter.c

diff --git a/ghc/rts/Interpreter.c b/ghc/rts/Interpreter.c
index 89a5e59..d39becb 100644 (file)
--- a/ghc/rts/Interpreter.c
+++ b/ghc/rts/Interpreter.c
@@ -672,12 +672,8 @@ run_BCO_return:
        Sp--; Sp[0] = (W_)&stg_enter_info;
        RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
     }
-    
-    // "Standard" stack check
-    if (Sp - (INTERP_STACK_CHECK_THRESH+1) < SpLim) {
-       Sp--; Sp[0] = (W_)&stg_enter_info;
-       RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
-    }
+    // Stack checks aren't necessary at return points, the stack use
+    // is aggregated into the enclosing function entry point.
     goto run_BCO;
     
 run_BCO_return_unboxed:
@@ -685,11 +681,8 @@ run_BCO_return_unboxed:
     if (doYouWantToGC()) {
        RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
     }
-    
-    // "Standard" stack check
-    if (Sp - (INTERP_STACK_CHECK_THRESH+1) < SpLim) {
-       RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
-    }
+    // Stack checks aren't necessary at return points, the stack use
+    // is aggregated into the enclosing function entry point.
     goto run_BCO;
     
 run_BCO_fun:
@@ -709,8 +702,8 @@ run_BCO_fun:
        RETURN_TO_SCHEDULER(ThreadInterpret, HeapOverflow);
     }
     
-    // "Standard" stack check
-    if (Sp - (INTERP_STACK_CHECK_THRESH+1) < SpLim) {
+    // Stack check
+    if (Sp - INTERP_STACK_CHECK_THRESH < SpLim) {
        Sp -= 2; 
        Sp[1] = (W_)obj; 
        Sp[0] = (W_)&stg_apply_interp_info; // placeholder, really
@@ -766,15 +759,19 @@ run_BCO:
 
        switch (BCO_NEXT) {
 
-       case bci_STKCHECK: 
-       {
-           // An explicit stack check; we hope these will be rare.
+       case bci_STKCHECK: {
+           // Explicit stack check at the beginning of a function
+           // *only* (stack checks in case alternatives are
+           // propagated to the enclosing function).
            int stk_words_reqd = BCO_NEXT + 1;
            if (Sp - stk_words_reqd < SpLim) {
-               Sp--; Sp[0] = (W_)obj;
+               Sp -= 2; 
+               Sp[1] = (W_)obj; 
+               Sp[0] = (W_)&stg_apply_interp_info;
                RETURN_TO_SCHEDULER(ThreadInterpret, StackOverflow);
+           } else {
+               goto nextInsn;
            }
-           goto nextInsn;
        }
 
        case bci_PUSH_L: {