Tighten up the code sequence for the combined interrupt and stack

check.  New sequence is same number of instructions, but eliminates a
load-delay interlock.  Sequence can perhaps be shortened by one
additional instruction.

diff --git a/v7/src/compiler/machines/spectrum/rules3.scm b/v7/src/compiler/machines/spectrum/rules3.scm
index cc2667911cf28d3abd802bab655e48e9c5ea3729..99752e155d75d083eb501bdf0dde83db79957ffe 100644 (file)
--- a/v7/src/compiler/machines/spectrum/rules3.scm
+++ b/v7/src/compiler/machines/spectrum/rules3.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: rules3.scm,v 4.34 1992/09/26 04:13:26 cph Exp $
+$Id: rules3.scm,v 4.35 1992/09/26 15:56:19 cph Exp $
 
 Copyright (c) 1988-92 Massachusetts Institute of Technology
 
@@ -429,26 +429,32 @@ MIT in each case. |#
         ,@(interrupt-check gc-label))))
 
 (define (interrupt-check gc-label)
-  (if (not (eq? 'OUT-OF-LINE compiler:generate-stack-checks?))
-      (LAP (COMB (>=) ,regnum:free-pointer ,regnum:memtop-pointer
-                (@PCR ,gc-label))
-          (LDW () ,reg:memtop ,regnum:memtop-pointer)
-          ,@(if compiler:generate-stack-checks?
-                (LAP (LDW () ,reg:stack-guard ,regnum:addil-result)
-                     (COMB (<=) ,regnum:stack-pointer ,regnum:addil-result
-                           (@PCR ,gc-label))
-                     (NOP ()))
-                (LAP)))
-      (let ((label (generate-label)))
-       (LAP (BLE ()
-                 (OFFSET ,hook:compiler-stack-and-interrupt-check
-                         4
-                         ,regnum:scheme-to-interface-ble))
-            ;; Assumes that (<= #x-2000 (- ,gc-label ,label) #x1fff)
-            ;; otherwise this assembles to two instructions, and it
-            ;; won't fit in the branch-delay slot.
-            (LDI () (- ,gc-label ,label) ,regnum:first-arg)
-            (LABEL ,label)))))
+  (case compiler:generate-stack-checks?
+    ((#F)
+     (LAP (COMB (>=) ,regnum:free-pointer ,regnum:memtop-pointer
+               (@PCR ,gc-label))
+         (LDW () ,reg:memtop ,regnum:memtop-pointer)))
+    ((OUT-OF-LINE)
+     (let ((label (generate-label)))
+       (LAP (BLE ()
+                (OFFSET ,hook:compiler-stack-and-interrupt-check
+                        4
+                        ,regnum:scheme-to-interface-ble))
+           ;; Assumes that (<= #x-2000 (- ,gc-label ,label) #x1fff)
+           ;; otherwise this assembles to two instructions, and it
+           ;; won't fit in the branch-delay slot.
+           (LDI () (- ,gc-label ,label) ,regnum:first-arg)
+           (LABEL ,label))))
+    (else
+     (LAP (LDW () ,reg:stack-guard ,regnum:first-arg)
+         (COMB (>=) ,regnum:free-pointer ,regnum:memtop-pointer
+               (@PCR ,gc-label))
+         ;; I think the next two instructions could be interchanged,
+         ;; allowing the NOP to be eliminated, but since I don't have
+         ;; the PA-RISC programming manual here I can't be sure. -- CPH
+         (LDW () ,reg:memtop ,regnum:memtop-pointer)
+         (COMB (<=) ,regnum:stack-pointer ,regnum:first-arg (@PCR ,gc-label))
+         (NOP ())))))
 \f
 (define-rule statement
   (CONTINUATION-ENTRY (? internal-label))