[project @ 2004-08-13 10:45:16 by simonmar]

[ghc-hetmet.git] / ghc / rts / Apply.hc

diff --git a/ghc/rts/Apply.hc b/ghc/rts/Apply.hc
index fc445c9..30fbb50 100644 (file)
--- a/ghc/rts/Apply.hc
+++ b/ghc/rts/Apply.hc
@@ -64,8 +64,13 @@ stg_ap_0_ret(void)
    the stack check fails, we can just push the PAP on the stack and
    return to the scheduler.
 
-   On entry: R1 points to the PAP.  The rest of the function's arguments
-   (*all* of 'em) are on the stack, starting at Sp[0].
+   On entry: R1 points to the PAP.  The rest of the function's
+   arguments (apart from those that are already in the PAP) are on the
+   stack, starting at Sp[0].  R2 contains an info table which
+   describes these arguments, which is used in the event that the
+   stack check in the entry code below fails.  The info table is
+   currently one of the stg_ap_*_ret family, as this code is always
+   entered from those functions.
 
    The idea is to copy the chunk of stack from the PAP object onto the
    stack / into registers, and enter the function.
@@ -88,13 +93,14 @@ STGFUN(stg_PAP_entry)
   // We have a hand-rolled stack check fragment here, because none of
   // the canned ones suit this situation.
   if ((Sp - Words) < SpLim) {
-      // there is a return address on the stack in the event of a
+      // there is a return address in R2 in the event of a
       // stack check failure.  The various stg_apply functions arrange
       // this before calling stg_PAP_entry.
+      Sp--; 
+      Sp[0] = R2.w;
       JMP_(stg_gc_unpt_r1);
   }
-  // Sp is already pointing one word below the arguments...
-  Sp -= Words-1;
+  Sp -= Words;
 
   // profiling
   TICK_ENT_PAP(pap);
@@ -157,8 +163,11 @@ STGFUN(stg_AP_entry)
   
   Words = ap->n_args;
 
-  // Check for stack overflow.
-  STK_CHK_GEN(Words+sizeofW(StgUpdateFrame), R1_PTR, stg_AP_entry);
+  // Check for stack overflow.  IMPORTANT: use a _NP check here,
+  // because if the check fails, we might end up blackholing this very
+  // closure, in which case we must enter the blackhole on return rather
+  // than continuing to evaluate the now-defunct closure.
+  STK_CHK_NP(Words+sizeofW(StgUpdateFrame),);
 
   PUSH_UPD_FRAME(R1.p, 0);
   Sp -= sizeofW(StgUpdateFrame) + Words;
@@ -224,8 +233,11 @@ STGFUN(stg_AP_STACK_entry)
   
   Words = ap->size;
 
-  // Check for stack overflow.
-  STK_CHK_GEN(Words+sizeofW(StgUpdateFrame), R1_PTR, stg_AP_STACK_entry);
+  // Check for stack overflow.  IMPORTANT: use a _NP check here,
+  // because if the check fails, we might end up blackholing this very
+  // closure, in which case we must enter the blackhole on return rather
+  // than continuing to evaluate the now-defunct closure.
+  STK_CHK_NP(Words+sizeofW(StgUpdateFrame),);
 
   PUSH_UPD_FRAME(R1.p, 0);
   Sp -= sizeofW(StgUpdateFrame) + Words;