X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fppc%2Fcall.lisp;h=0dab7f0302484c5b8dcbfa84faec5d31c90efd27;hb=293488f3b117854e12b0d7f4faeb742b707bbc9c;hp=a670118a5e620e54be87ed2a92fbcf8d7883aaed;hpb=6365d636fa30ff3e2c2ebc9668f978fa0ebc7a0e;p=sbcl.git

diff --git a/src/compiler/ppc/call.lisp b/src/compiler/ppc/call.lisp
index a670118..0dab7f0 100644
--- a/src/compiler/ppc/call.lisp
+++ b/src/compiler/ppc/call.lisp
@@ -19,7 +19,7 @@
   (declare (type unsigned-byte n))
   (if (< n register-arg-count)
       (make-wired-tn *backend-t-primitive-type* register-arg-scn
-		     (elt *register-arg-offsets* n))
+                     (elt *register-arg-offsets* n))
       (make-wired-tn *backend-t-primitive-type* control-stack-arg-scn n)))
 
 
@@ -50,14 +50,14 @@
   (specify-save-tn
    (physenv-debug-live-tn (make-normal-tn *fixnum-primitive-type*) env)
    (make-wired-tn *fixnum-primitive-type*
-		  control-stack-arg-scn
-		  ocfp-save-offset)))
+                  control-stack-arg-scn
+                  ocfp-save-offset)))
 (!def-vm-support-routine make-return-pc-save-location (env)
   (specify-save-tn
    (physenv-debug-live-tn (make-normal-tn *backend-t-primitive-type*) env)
    (make-wired-tn *backend-t-primitive-type*
-		  control-stack-arg-scn
-		  lra-save-offset)))
+                  control-stack-arg-scn
+                  lra-save-offset)))
 
 ;;; Make a TN for the standard argument count passing location.  We
 ;;; only need to make the standard location, since a count is never
@@ -82,7 +82,7 @@
 ;;; continuation within a function.
 (!def-vm-support-routine make-unknown-values-locations ()
   (list (make-stack-pointer-tn)
-	(make-normal-tn *fixnum-primitive-type*)))
+        (make-normal-tn *fixnum-primitive-type*)))
 
 ;;; This function is called by the ENTRY-ANALYZE phase, allowing
 ;;; VM-dependent initialization of the IR2-COMPONENT structure.  We push
@@ -92,17 +92,17 @@
   (declare (type component component))
   (dotimes (i code-constants-offset)
     (vector-push-extend nil
-			(ir2-component-constants (component-info component))))
+                        (ir2-component-constants (component-info component))))
   (values))
 
 ;;;; Frame hackery:
 
-;;; this is the first function in this file that differs materially from 
+;;; this is the first function in this file that differs materially from
 ;;; ../alpha/call.lisp
 (defun bytes-needed-for-non-descriptor-stack-frame ()
   (logandc2 (+ +stack-alignment-bytes+ number-stack-displacement
-	       (* (sb-allocated-size 'non-descriptor-stack) n-word-bytes))
-	    +stack-alignment-bytes+))
+               (* (sb-allocated-size 'non-descriptor-stack) n-word-bytes))
+            +stack-alignment-bytes+))
 
 
 ;;; Used for setting up the Old-FP in local call.
@@ -119,7 +119,25 @@
   (:generator 1
     (let ((nfp (current-nfp-tn vop)))
       (when nfp
-	(inst addi val nfp (bytes-needed-for-non-descriptor-stack-frame))))))
+        (inst addi val nfp (bytes-needed-for-non-descriptor-stack-frame))))))
+
+;;; Accessing a slot from an earlier stack frame is definite hackery.
+(define-vop (ancestor-frame-ref)
+  (:args (frame-pointer :scs (descriptor-reg))
+         (variable-home-tn :load-if nil))
+  (:results (value :scs (descriptor-reg any-reg)))
+  (:policy :fast-safe)
+  (:generator 4
+    (aver (sc-is variable-home-tn control-stack))
+    (loadw value frame-pointer (tn-offset variable-home-tn))))
+(define-vop (ancestor-frame-set)
+  (:args (frame-pointer :scs (descriptor-reg))
+         (value :scs (descriptor-reg any-reg)))
+  (:results (variable-home-tn :load-if nil))
+  (:policy :fast-safe)
+  (:generator 4
+    (aver (sc-is variable-home-tn control-stack))
+    (storew value frame-pointer (tn-offset variable-home-tn))))
 
 (define-vop (xep-allocate-frame)
   (:info start-lab copy-more-arg-follows)
@@ -129,7 +147,7 @@
   (:generator 1
     ;; Make sure the function is aligned, and drop a label pointing to this
     ;; function header.
-    (align n-lowtag-bits)
+    (emit-alignment n-lowtag-bits)
     (trace-table-entry trace-table-fun-prologue)
     (emit-label start-lab)
     ;; Allocate function header.
@@ -138,34 +156,34 @@
       (inst word 0))
     (let* ((entry-point (gen-label)))
       (emit-label entry-point)
-      (inst compute-code-from-fn code-tn lip-tn entry-point temp))
+      (inst compute-code-from-lip code-tn lip-tn entry-point temp))
       ;; FIXME alpha port has a ### note here saying we should "save it
       ;; on the stack" so that GC sees it. No idea what "it" is -dan 20020110
     ;; Build our stack frames.
     (inst addi csp-tn cfp-tn
-	  (* n-word-bytes (sb-allocated-size 'control-stack)))
+          (* n-word-bytes (sb-allocated-size 'control-stack)))
     (let ((nfp-tn (current-nfp-tn vop)))
       (when nfp-tn
-	(let* ((nbytes (bytes-needed-for-non-descriptor-stack-frame)))
-	  (when (> nbytes number-stack-displacement)
-	    (inst stwu nsp-tn nsp-tn (- nbytes))
-	    (inst addi nfp-tn nsp-tn number-stack-displacement)))))
+        (let* ((nbytes (bytes-needed-for-non-descriptor-stack-frame)))
+          (when (> nbytes number-stack-displacement)
+            (inst stwu nsp-tn nsp-tn (- nbytes))
+            (inst addi nfp-tn nsp-tn number-stack-displacement)))))
     (trace-table-entry trace-table-normal)))
 
 (define-vop (allocate-frame)
   (:results (res :scs (any-reg))
-	    (nfp :scs (any-reg)))
+            (nfp :scs (any-reg)))
   (:info callee)
   (:generator 2
     (trace-table-entry trace-table-fun-prologue)
     (move res csp-tn)
     (inst addi csp-tn csp-tn
-	  (* n-word-bytes (sb-allocated-size 'control-stack)))
+          (* n-word-bytes (sb-allocated-size 'control-stack)))
     (when (ir2-physenv-number-stack-p callee)
       (let* ((nbytes (bytes-needed-for-non-descriptor-stack-frame)))
-	(when (> nbytes number-stack-displacement)
-	  (inst stwu nsp-tn nsp-tn (- (bytes-needed-for-non-descriptor-stack-frame)))
-	  (inst addi nfp nsp-tn number-stack-displacement))))
+        (when (> nbytes number-stack-displacement)
+          (inst stwu nsp-tn nsp-tn (- (bytes-needed-for-non-descriptor-stack-frame)))
+          (inst addi nfp nsp-tn number-stack-displacement))))
     (trace-table-entry trace-table-normal)))
 
 ;;; Allocate a partial frame for passing stack arguments in a full call.  Nargs
@@ -206,115 +224,115 @@
 ;;;
 ;;; The general-case code looks like this:
 #|
-	b regs-defaulted		; Skip if MVs
-	nop
+        b regs-defaulted                ; Skip if MVs
+        nop
 
-	move a1 null-tn			; Default register values
-	...
-	loadi nargs 1			; Force defaulting of stack values
-	move old-fp csp			; Set up args for SP resetting
+        move a1 null-tn                 ; Default register values
+        ...
+        loadi nargs 1                   ; Force defaulting of stack values
+        move old-fp csp                 ; Set up args for SP resetting
 
 regs-defaulted
-	subcc temp nargs register-arg-count
+        subcc temp nargs register-arg-count
 
-	b :lt default-value-7	; jump to default code
-	loadw move-temp ocfp-tn 6	; Move value to correct location.
+        b :lt default-value-7   ; jump to default code
+        loadw move-temp ocfp-tn 6       ; Move value to correct location.
         subcc temp 1
-	store-stack-tn val4-tn move-temp
+        store-stack-tn val4-tn move-temp
 
-	b :lt default-value-8
-	loadw move-temp ocfp-tn 7
+        b :lt default-value-8
+        loadw move-temp ocfp-tn 7
         subcc temp 1
-	store-stack-tn val5-tn move-temp
+        store-stack-tn val5-tn move-temp
 
-	...
+        ...
 
 defaulting-done
-	move csp ocfp			; Reset SP.
+        move csp ocfp                   ; Reset SP.
 <end of code>
 
 <elsewhere>
 default-value-7
-	store-stack-tn val4-tn null-tn	; Nil out 7'th value. (first on stack)
+        store-stack-tn val4-tn null-tn  ; Nil out 7'th value. (first on stack)
 
 default-value-8
-	store-stack-tn val5-tn null-tn	; Nil out 8'th value.
+        store-stack-tn val5-tn null-tn  ; Nil out 8'th value.
 
-	...
+        ...
 
-	br defaulting-done
+        br defaulting-done
         nop
 |#
 ;;; differences from alpha: (1) alpha tests for lra-label before
-;;; compute-code-from-lra and skips if nil. (2) loop termination is 
+;;; compute-code-from-lra and skips if nil. (2) loop termination is
 ;;; different when clearing stack defaults
 
 (defun default-unknown-values (vop values nvals move-temp temp lra-label)
   (declare (type (or tn-ref null) values)
-	   (type unsigned-byte nvals) (type tn move-temp temp))
+           (type unsigned-byte nvals) (type tn move-temp temp))
   (if (<= nvals 1)
       (progn
-	(sb!assem:without-scheduling ()
-	  (note-this-location vop :single-value-return)
-	  (move csp-tn ocfp-tn)
-	  (inst nop))
-	(inst compute-code-from-lra code-tn code-tn lra-label temp))
+        (sb!assem:without-scheduling ()
+          (note-this-location vop :single-value-return)
+          (move csp-tn ocfp-tn)
+          (inst nop))
+        (inst compute-code-from-lra code-tn lra-tn lra-label temp))
       (let ((regs-defaulted (gen-label))
-	    (defaulting-done (gen-label))
-	    (default-stack-vals (gen-label)))
-	;; Branch off to the MV case.
-	(sb!assem:without-scheduling ()
-	  (note-this-location vop :unknown-return)
-	  (if (> nvals register-arg-count)
-	      (inst addic. temp nargs-tn (- (fixnumize register-arg-count)))
-	      (move csp-tn ocfp-tn))
-	  (inst b regs-defaulted))
-	
-	;; Do the single value case.
-	(do ((i 1 (1+ i))
-	     (val (tn-ref-across values) (tn-ref-across val)))
-	    ((= i (min nvals register-arg-count)))
-	  (move (tn-ref-tn val) null-tn))
-	(when (> nvals register-arg-count)
-	  (move ocfp-tn csp-tn)
-	  (inst b default-stack-vals))
-	
-	(emit-label regs-defaulted)
-	(when (> nvals register-arg-count)
-	  (collect ((defaults))
-	    (do ((i register-arg-count (1+ i))
-		 (val (do ((i 0 (1+ i))
-			   (val values (tn-ref-across val)))
-			  ((= i register-arg-count) val))
-		      (tn-ref-across val)))
-		((null val))
-	      
-	      (let ((default-lab (gen-label))
-		    (tn (tn-ref-tn val)))
-		(defaults (cons default-lab tn))
-		
-		(inst lwz move-temp ocfp-tn (* i n-word-bytes))
-		(inst ble default-lab)
-		(inst addic. temp temp (- (fixnumize 1)))
-		(store-stack-tn tn move-temp)))
-	    
-	    (emit-label defaulting-done)
-	    (move csp-tn ocfp-tn)
-	    
-	    (let ((defaults (defaults)))
-	      (when defaults
-		(assemble (*elsewhere*)
-		  (emit-label default-stack-vals)
-		  (trace-table-entry trace-table-fun-prologue)
-		  (do ((remaining defaults (cdr remaining)))
-		      ((null remaining))
-		    (let ((def (car remaining)))
-		      (emit-label (car def))
-		      (store-stack-tn (cdr def) null-tn)))
-		  (inst b defaulting-done)
-		  (trace-table-entry trace-table-normal))))))
-
-	(inst compute-code-from-lra code-tn code-tn lra-label temp)))
+            (defaulting-done (gen-label))
+            (default-stack-vals (gen-label)))
+        ;; Branch off to the MV case.
+        (sb!assem:without-scheduling ()
+          (note-this-location vop :unknown-return)
+          (if (> nvals register-arg-count)
+              (inst addic. temp nargs-tn (- (fixnumize register-arg-count)))
+              (move csp-tn ocfp-tn))
+          (inst b regs-defaulted))
+
+        ;; Do the single value case.
+        (do ((i 1 (1+ i))
+             (val (tn-ref-across values) (tn-ref-across val)))
+            ((= i (min nvals register-arg-count)))
+          (move (tn-ref-tn val) null-tn))
+        (when (> nvals register-arg-count)
+          (move ocfp-tn csp-tn)
+          (inst b default-stack-vals))
+
+        (emit-label regs-defaulted)
+        (when (> nvals register-arg-count)
+          (collect ((defaults))
+            (do ((i register-arg-count (1+ i))
+                 (val (do ((i 0 (1+ i))
+                           (val values (tn-ref-across val)))
+                          ((= i register-arg-count) val))
+                      (tn-ref-across val)))
+                ((null val))
+
+              (let ((default-lab (gen-label))
+                    (tn (tn-ref-tn val)))
+                (defaults (cons default-lab tn))
+
+                (inst lwz move-temp ocfp-tn (* i n-word-bytes))
+                (inst ble default-lab)
+                (inst addic. temp temp (- (fixnumize 1)))
+                (store-stack-tn tn move-temp)))
+
+            (emit-label defaulting-done)
+            (move csp-tn ocfp-tn)
+
+            (let ((defaults (defaults)))
+              (when defaults
+                (assemble (*elsewhere*)
+                  (emit-label default-stack-vals)
+                  (trace-table-entry trace-table-fun-prologue)
+                  (do ((remaining defaults (cdr remaining)))
+                      ((null remaining))
+                    (let ((def (car remaining)))
+                      (emit-label (car def))
+                      (store-stack-tn (cdr def) null-tn)))
+                  (inst b defaulting-done)
+                  (trace-table-entry trace-table-normal))))))
+
+        (inst compute-code-from-lra code-tn lra-tn lra-label temp)))
   (values))
 
 
@@ -339,27 +357,27 @@ default-value-8
 (defun receive-unknown-values (args nargs start count lra-label temp)
   (declare (type tn args nargs start count temp))
   (let ((variable-values (gen-label))
-	(done (gen-label)))
+        (done (gen-label)))
     (sb!assem:without-scheduling ()
       (inst b variable-values)
       (inst nop))
-    
-    (inst compute-code-from-lra code-tn code-tn lra-label temp)
+
+    (inst compute-code-from-lra code-tn lra-tn lra-label temp)
     (inst addi csp-tn csp-tn 4)
     (storew (first *register-arg-tns*) csp-tn -1)
     (inst subi start csp-tn 4)
     (inst li count (fixnumize 1))
-    
+
     (emit-label done)
-    
+
     (assemble (*elsewhere*)
       (trace-table-entry trace-table-fun-prologue)
       (emit-label variable-values)
-      (inst compute-code-from-lra code-tn code-tn lra-label temp)
+      (inst compute-code-from-lra code-tn lra-tn lra-label temp)
       (do ((arg *register-arg-tns* (rest arg))
-	   (i 0 (1+ i)))
-	  ((null arg))
-	(storew (first arg) args i))
+           (i 0 (1+ i)))
+          ((null arg))
+        (storew (first arg) args i))
       (move start args)
       (move count nargs)
       (inst b done)
@@ -374,13 +392,22 @@ default-value-8
    (start :scs (any-reg))
    (count :scs (any-reg)))
   (:temporary (:sc descriptor-reg :offset ocfp-offset
-		   :from :eval :to (:result 0))
-	      values-start)
+                   :from :eval :to (:result 0))
+              values-start)
   (:temporary (:sc any-reg :offset nargs-offset
-	       :from :eval :to (:result 1))
-	      nvals)
+               :from :eval :to (:result 1))
+              nvals)
   (:temporary (:scs (non-descriptor-reg)) temp))
 
+
+;;; This hook in the codegen pass lets us insert code before fall-thru entry
+;;; points, local-call entry points, and tail-call entry points.  The default
+;;; does nothing.
+(defun emit-block-header (start-label trampoline-label fall-thru-p alignp)
+  (declare (ignore fall-thru-p alignp))
+  (when trampoline-label
+    (emit-label trampoline-label))
+  (emit-label start-label))
 
 
 ;;;; Local call with unknown values convention return:
@@ -404,8 +431,8 @@ default-value-8
 ;;; MAYBE-LOAD-STACK-TN.
 (define-vop (call-local)
   (:args (fp)
-	 (nfp)
-	 (args :more t))
+         (nfp)
+         (args :more t))
   (:results (values :more t))
   (:save-p t)
   (:move-args :local-call)
@@ -419,15 +446,15 @@ default-value-8
   (:generator 5
     (trace-table-entry trace-table-call-site)
     (let ((label (gen-label))
-	  (cur-nfp (current-nfp-tn vop)))
+          (cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(store-stack-tn nfp-save cur-nfp))
+        (store-stack-tn nfp-save cur-nfp))
       (let ((callee-nfp (callee-nfp-tn callee)))
-	(when callee-nfp
-	  (maybe-load-stack-tn callee-nfp nfp)))
+        (when callee-nfp
+          (maybe-load-stack-tn callee-nfp nfp)))
       (maybe-load-stack-tn cfp-tn fp)
       (inst compute-lra-from-code
-	    (callee-return-pc-tn callee) code-tn label temp)
+            (callee-return-pc-tn callee) code-tn label temp)
       (note-this-location vop :call-site)
       (inst b target)
       (emit-return-pc label)
@@ -435,7 +462,7 @@ default-value-8
       ;; alpha uses (maybe-load-stack-nfp-tn cur-nfp nfp-save temp)
       ;; instead of the clause below
       (when cur-nfp
-	(load-stack-tn cur-nfp nfp-save)))
+        (load-stack-tn cur-nfp nfp-save)))
     (trace-table-entry trace-table-normal)))
 
 
@@ -448,8 +475,8 @@ default-value-8
 ;;; MAYBE-LOAD-STACK-TN.
 (define-vop (multiple-call-local unknown-values-receiver)
   (:args (fp)
-	 (nfp)
-	 (args :more t))
+         (nfp)
+         (args :more t))
   (:save-p t)
   (:move-args :local-call)
   (:info save callee target)
@@ -460,23 +487,23 @@ default-value-8
   (:generator 20
     (trace-table-entry trace-table-call-site)
     (let ((label (gen-label))
-	  (cur-nfp (current-nfp-tn vop)))
+          (cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(store-stack-tn nfp-save cur-nfp))
+        (store-stack-tn nfp-save cur-nfp))
       (let ((callee-nfp (callee-nfp-tn callee)))
-	;; alpha doesn't test this before the maybe-load
-	(when callee-nfp
-	  (maybe-load-stack-tn callee-nfp nfp)))
+        ;; alpha doesn't test this before the maybe-load
+        (when callee-nfp
+          (maybe-load-stack-tn callee-nfp nfp)))
       (maybe-load-stack-tn cfp-tn fp)
       (inst compute-lra-from-code
-	    (callee-return-pc-tn callee) code-tn label temp)
+            (callee-return-pc-tn callee) code-tn label temp)
       (note-this-location vop :call-site)
       (inst b target)
       (emit-return-pc label)
       (note-this-location vop :unknown-return)
       (receive-unknown-values values-start nvals start count label temp)
       (when cur-nfp
-	(load-stack-tn cur-nfp nfp-save)))
+        (load-stack-tn cur-nfp nfp-save)))
     (trace-table-entry trace-table-normal)))
 
 
@@ -490,8 +517,8 @@ default-value-8
 ;;; MAYBE-LOAD-STACK-TN.
 (define-vop (known-call-local)
   (:args (fp)
-	 (nfp)
-	 (args :more t))
+         (nfp)
+         (args :more t))
   (:results (res :more t))
   (:move-args :local-call)
   (:save-p t)
@@ -503,21 +530,21 @@ default-value-8
   (:generator 5
     (trace-table-entry trace-table-call-site)
     (let ((label (gen-label))
-	  (cur-nfp (current-nfp-tn vop)))
+          (cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(store-stack-tn nfp-save cur-nfp))
+        (store-stack-tn nfp-save cur-nfp))
       (let ((callee-nfp (callee-nfp-tn callee)))
-	(when callee-nfp
-	  (maybe-load-stack-tn callee-nfp nfp)))
+        (when callee-nfp
+          (maybe-load-stack-tn callee-nfp nfp)))
       (maybe-load-stack-tn cfp-tn fp)
       (inst compute-lra-from-code
-	    (callee-return-pc-tn callee) code-tn label temp)
+            (callee-return-pc-tn callee) code-tn label temp)
       (note-this-location vop :call-site)
       (inst b target)
       (emit-return-pc label)
       (note-this-location vop :known-return)
       (when cur-nfp
-	(load-stack-tn cur-nfp nfp-save)))
+        (load-stack-tn cur-nfp nfp-save)))
     (trace-table-entry trace-table-normal)))
 
 ;;; Return from known values call.  We receive the return locations as
@@ -529,8 +556,8 @@ default-value-8
 ;;; MAYBE-LOAD-STACK-TN.
 (define-vop (known-return)
   (:args (old-fp :target old-fp-temp)
-	 (return-pc :target return-pc-temp)
-	 (vals :more t))
+         (return-pc :target return-pc-temp)
+         (vals :more t))
   (:temporary (:sc any-reg :from (:argument 0)) old-fp-temp)
   (:temporary (:sc descriptor-reg :from (:argument 1)) return-pc-temp)
   (:move-args :known-return)
@@ -544,9 +571,9 @@ default-value-8
     (move csp-tn cfp-tn)
     (let ((cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(inst addi nsp-tn cur-nfp 
-	      (- (bytes-needed-for-non-descriptor-stack-frame)
-		 number-stack-displacement))))
+        (inst addi nsp-tn cur-nfp
+              (- (bytes-needed-for-non-descriptor-stack-frame)
+                 number-stack-displacement))))
     (move cfp-tn old-fp-temp)
     (inst j return-pc-temp (- n-word-bytes other-pointer-lowtag))
     (trace-table-entry trace-table-normal)))
@@ -569,7 +596,7 @@ default-value-8
 ;;; replication in defining the cross-product VOPs.
 ;;;
 ;;; NAME is the name of the VOP to define.
-;;; 
+;;;
 ;;; NAMED is true if the first argument is a symbol whose global function
 ;;; definition is to be called.
 ;;;
@@ -594,210 +621,252 @@ default-value-8
 (defmacro define-full-call (name named return variable)
   (aver (not (and variable (eq return :tail))))
   `(define-vop (,name
-		,@(when (eq return :unknown)
-		    '(unknown-values-receiver)))
+                ,@(when (eq return :unknown)
+                    '(unknown-values-receiver)))
      (:args
       ,@(unless (eq return :tail)
-	  '((new-fp :scs (any-reg) :to :eval)))
+          '((new-fp :scs (any-reg) :to :eval)))
 
       ,(if named
-	   '(name :target name-pass)
-	   '(arg-fun :target lexenv))
-      
+           '(name :target name-pass)
+           '(arg-fun :target lexenv))
+
       ,@(when (eq return :tail)
-	  '((old-fp :target old-fp-pass)
-	    (return-pc :target return-pc-pass)))
-      
+          '((old-fp :target old-fp-pass)
+            (return-pc :target return-pc-pass)))
+
       ,@(unless variable '((args :more t :scs (descriptor-reg)))))
 
      ,@(when (eq return :fixed)
-	 '((:results (values :more t))))
-   
+         '((:results (values :more t))))
+
      (:save-p ,(if (eq return :tail) :compute-only t))
 
      ,@(unless (or (eq return :tail) variable)
-	 '((:move-args :full-call)))
+         '((:move-args :full-call)))
 
-     (:vop-var vop)
-     (:info ,@(unless (or variable (eq return :tail)) '(arg-locs))
-	    ,@(unless variable '(nargs))
-	    ,@(when (eq return :fixed) '(nvals)))
+    (:vop-var vop)
+    (:info ,@(unless (or variable (eq return :tail)) '(arg-locs))
+           ,@(unless variable '(nargs))
+           ,@(when (eq return :fixed) '(nvals))
+           step-instrumenting)
 
      (:ignore
       ,@(unless (or variable (eq return :tail)) '(arg-locs))
       ,@(unless variable '(args)))
 
      (:temporary (:sc descriptor-reg
-		  :offset ocfp-offset
-		  :from (:argument 1)
-		  ,@(unless (eq return :fixed)
-		      '(:to :eval)))
-		 old-fp-pass)
+                  :offset ocfp-offset
+                  :from (:argument 1)
+                  ,@(unless (eq return :fixed)
+                      '(:to :eval)))
+                 old-fp-pass)
 
      (:temporary (:sc descriptor-reg
-		  :offset lra-offset
-		  :from (:argument ,(if (eq return :tail) 2 1))
-		  :to :eval)
-		 return-pc-pass)
+                  :offset lra-offset
+                  :from (:argument ,(if (eq return :tail) 2 1))
+                  :to :eval)
+                 return-pc-pass)
 
      ,(if named
-	  `(:temporary (:sc descriptor-reg :offset fdefn-offset ; -dan
-			    :from (:argument ,(if (eq return :tail) 0 1))
-			    :to :eval)
-		       name-pass)
-	  `(:temporary (:sc descriptor-reg :offset lexenv-offset
-			    :from (:argument ,(if (eq return :tail) 0 1))
-			    :to :eval)
-		       lexenv))
-     ,@(unless named
-	 '((:temporary (:scs (descriptor-reg) :from (:argument 0) :to :eval)
-	               function)))
+          `(:temporary (:sc descriptor-reg :offset fdefn-offset ; -dan
+                            :from (:argument ,(if (eq return :tail) 0 1))
+                            :to :eval)
+                       name-pass)
+          `(:temporary (:sc descriptor-reg :offset lexenv-offset
+                            :from (:argument ,(if (eq return :tail) 0 1))
+                            :to :eval)
+                       lexenv))
+     (:temporary (:scs (descriptor-reg) :from (:argument 0) :to :eval)
+                 function)
      (:temporary (:sc any-reg :offset nargs-offset :to :eval)
-		 nargs-pass)
+                 nargs-pass)
 
      ,@(when variable
-	 (mapcar #'(lambda (name offset)
-		     `(:temporary (:sc descriptor-reg
-				   :offset ,offset
-				   :to :eval)
-			 ,name))
-		 register-arg-names *register-arg-offsets*))
+         (mapcar #'(lambda (name offset)
+                     `(:temporary (:sc descriptor-reg
+                                   :offset ,offset
+                                   :to :eval)
+                         ,name))
+                 register-arg-names *register-arg-offsets*))
      ,@(when (eq return :fixed)
-	 '((:temporary (:scs (descriptor-reg) :from :eval) move-temp)))
+         '((:temporary (:scs (descriptor-reg) :from :eval) move-temp)))
+
+     (:temporary (:scs (descriptor-reg) :to :eval) stepping)
 
      ,@(unless (eq return :tail)
-	 '((:temporary (:scs (non-descriptor-reg)) temp)
-	   (:temporary (:sc control-stack :offset nfp-save-offset) nfp-save)))
+         '((:temporary (:scs (non-descriptor-reg)) temp)
+           (:temporary (:sc control-stack :offset nfp-save-offset) nfp-save)))
 
      (:temporary (:sc interior-reg :offset lip-offset) entry-point)
 
      (:generator ,(+ (if named 5 0)
-		     (if variable 19 1)
-		     (if (eq return :tail) 0 10)
-		     15
-		     (if (eq return :unknown) 25 0))
+                     (if variable 19 1)
+                     (if (eq return :tail) 0 10)
+                     15
+                     (if (eq return :unknown) 25 0))
        (trace-table-entry trace-table-call-site)
+
        (let* ((cur-nfp (current-nfp-tn vop))
-	      ,@(unless (eq return :tail)
-		  '((lra-label (gen-label))))
-	      (filler
-	       (remove nil
-		       (list :load-nargs
-			     ,@(if (eq return :tail)
-				   '((unless (location= old-fp old-fp-pass)
-				       :load-old-fp)
-				     (unless (location= return-pc
-							return-pc-pass)
-				       :load-return-pc)
-				     (when cur-nfp
-				       :frob-nfp))
-				   '(:comp-lra
-				     (when cur-nfp
-				       :frob-nfp)
-				     :save-fp
-				     :load-fp))))))
-	 (flet ((do-next-filler ()
-		  (let* ((next (pop filler))
-			 (what (if (consp next) (car next) next)))
-		    (ecase what
-		      (:load-nargs
-		       ,@(if variable
-			     `((inst sub nargs-pass csp-tn new-fp)
-			       ,@(let ((index -1))
-				   (mapcar #'(lambda (name)
-					       `(loadw ,name new-fp
-						       ,(incf index)))
-					   register-arg-names)))
-			     '((inst lr nargs-pass (fixnumize nargs)))))
-		      ,@(if (eq return :tail)
-			    '((:load-old-fp
-			       (sc-case old-fp
-				 (any-reg
-				  (inst mr old-fp-pass old-fp))
-				 (control-stack
-				  (loadw old-fp-pass cfp-tn
-					 (tn-offset old-fp)))))
-			      (:load-return-pc
-			       (sc-case return-pc
-				 (descriptor-reg
-				  (inst mr return-pc-pass return-pc))
-				 (control-stack
-				  (loadw return-pc-pass cfp-tn
-					 (tn-offset return-pc)))))
-			      (:frob-nfp
-			       (inst addi nsp-tn cur-nfp
-				     (- (bytes-needed-for-non-descriptor-stack-frame)
-					number-stack-displacement))))
-			    `((:comp-lra
-			       (inst compute-lra-from-code
-				     return-pc-pass code-tn lra-label temp))
-			      (:frob-nfp
-			       (store-stack-tn nfp-save cur-nfp))
-			      (:save-fp
-			       (inst mr old-fp-pass cfp-tn))
-			      (:load-fp
-			       ,(if variable
-				    '(move cfp-tn new-fp)
-				    '(if (> nargs register-arg-count)
-					 (move cfp-tn new-fp)
-					 (move cfp-tn csp-tn))))))
-		      ((nil))))))
-	   ,@(if named
-		 `((sc-case name
-		     (descriptor-reg (move name-pass name))
-		     (control-stack
-		      (loadw name-pass cfp-tn (tn-offset name))
-		      (do-next-filler))
-		     (constant
-		      (loadw name-pass code-tn (tn-offset name)
-			     other-pointer-lowtag)
-		      (do-next-filler)))
-		   (loadw entry-point name-pass fdefn-raw-addr-slot
-			  other-pointer-lowtag)
-		   (do-next-filler))
-		 `((sc-case arg-fun
-		     (descriptor-reg (move lexenv arg-fun))
-		     (control-stack
-		      (loadw lexenv cfp-tn (tn-offset arg-fun))
-		      (do-next-filler))
-		     (constant
-		      (loadw lexenv code-tn (tn-offset arg-fun)
-			     other-pointer-lowtag)
-		      (do-next-filler)))
-		   (loadw function lexenv closure-fun-slot
-		    fun-pointer-lowtag)
-		   (do-next-filler)
-		   (inst addi entry-point function
-		    (- (ash simple-fun-code-offset word-shift)
-		     fun-pointer-lowtag))
-		   ))
-	   (loop
-	     (if filler
-		 (do-next-filler)
-		 (return)))
-	   
-	   (note-this-location vop :call-site)
-	   (inst mtctr entry-point)
-	   ;; this following line is questionable.  or else the alpha
-	   ;; code (which doesn't do it) is questionable
-	   ;; (inst mr code-tn function)
-	   (inst bctr))
-
-	 ,@(ecase return
-	     (:fixed
-	      '((emit-return-pc lra-label)
-		(default-unknown-values vop values nvals move-temp
-					temp lra-label)
-		(when cur-nfp
-		  (load-stack-tn cur-nfp nfp-save))))
-	     (:unknown
-	      '((emit-return-pc lra-label)
-		(note-this-location vop :unknown-return)
-		(receive-unknown-values values-start nvals start count
-					lra-label temp)
-		(when cur-nfp
-		  (load-stack-tn cur-nfp nfp-save))))
-	     (:tail)))
+              ,@(unless (eq return :tail)
+                  '((lra-label (gen-label))))
+              (step-done-label (gen-label))
+              (filler
+               (remove nil
+                       (list :load-nargs
+                             ,@(if (eq return :tail)
+                                   '((unless (location= old-fp old-fp-pass)
+                                       :load-old-fp)
+                                     (unless (location= return-pc
+                                                        return-pc-pass)
+                                       :load-return-pc)
+                                     (when cur-nfp
+                                       :frob-nfp))
+                                   '(:comp-lra
+                                     (when cur-nfp
+                                       :frob-nfp)
+                                     :save-fp
+                                     :load-fp))))))
+         (flet ((do-next-filler ()
+                  (let* ((next (pop filler))
+                         (what (if (consp next) (car next) next)))
+                    (ecase what
+                      (:load-nargs
+                       ,@(if variable
+                             `((inst sub nargs-pass csp-tn new-fp)
+                               ,@(let ((index -1))
+                                   (mapcar #'(lambda (name)
+                                               `(loadw ,name new-fp
+                                                       ,(incf index)))
+                                           register-arg-names)))
+                             '((inst lr nargs-pass (fixnumize nargs)))))
+                      ,@(if (eq return :tail)
+                            '((:load-old-fp
+                               (sc-case old-fp
+                                 (any-reg
+                                  (inst mr old-fp-pass old-fp))
+                                 (control-stack
+                                  (loadw old-fp-pass cfp-tn
+                                         (tn-offset old-fp)))))
+                              (:load-return-pc
+                               (sc-case return-pc
+                                 (descriptor-reg
+                                  (inst mr return-pc-pass return-pc))
+                                 (control-stack
+                                  (loadw return-pc-pass cfp-tn
+                                         (tn-offset return-pc)))))
+                              (:frob-nfp
+                               (inst addi nsp-tn cur-nfp
+                                     (- (bytes-needed-for-non-descriptor-stack-frame)
+                                        number-stack-displacement))))
+                            `((:comp-lra
+                               (inst compute-lra-from-code
+                                     return-pc-pass code-tn lra-label temp))
+                              (:frob-nfp
+                               (store-stack-tn nfp-save cur-nfp))
+                              (:save-fp
+                               (inst mr old-fp-pass cfp-tn))
+                              (:load-fp
+                               ,(if variable
+                                    '(move cfp-tn new-fp)
+                                    '(if (> nargs register-arg-count)
+                                         (move cfp-tn new-fp)
+                                         (move cfp-tn csp-tn))))))
+                      ((nil)))))
+                (insert-step-instrumenting (callable-tn)
+                  ;; Conditionally insert a conditional trap:
+                  (when step-instrumenting
+                    ;; Get the symbol-value of SB!IMPL::*STEPPING*
+                    #!-sb-thread
+                    (load-symbol-value stepping sb!impl::*stepping*)
+                    #!+sb-thread
+                    (loadw stepping thread-base-tn thread-stepping-slot)
+                    (inst cmpw stepping null-tn)
+                    ;; If it's not null, trap.
+                    (inst beq step-done-label)
+                    ;; CONTEXT-PC will be pointing here when the
+                    ;; interrupt is handled, not after the UNIMP.
+                    (note-this-location vop :step-before-vop)
+                    ;; Construct a trap code with the low bits from
+                    ;; SINGLE-STEP-AROUND-TRAP and the high bits from
+                    ;; the register number of CALLABLE-TN.
+                    (inst unimp (logior single-step-around-trap
+                                        (ash (reg-tn-encoding callable-tn)
+                                             5)))
+                    (emit-label step-done-label))))
+           ,@(if named
+                 `((sc-case name
+                     (descriptor-reg (move name-pass name))
+                     (control-stack
+                      (loadw name-pass cfp-tn (tn-offset name))
+                      (do-next-filler))
+                     (constant
+                      (loadw name-pass code-tn (tn-offset name)
+                             other-pointer-lowtag)
+                      (do-next-filler)))
+                   ;; The step instrumenting must be done after
+                   ;; FUNCTION is loaded, but before ENTRY-POINT is
+                   ;; calculated.
+                   (insert-step-instrumenting name-pass)
+                   ;; The raw-addr (ENTRY-POINT) will be one of:
+                   ;; closure_tramp, undefined_tramp, or somewhere
+                   ;; within a simple-fun object.  If the latter, then
+                   ;; it is essential (due to it being an interior
+                   ;; pointer) that the function itself be in a
+                   ;; register before the raw-addr is loaded.
+                   (sb!assem:without-scheduling ()
+                     (loadw function name-pass fdefn-fun-slot
+                            other-pointer-lowtag)
+                     (loadw entry-point name-pass fdefn-raw-addr-slot
+                            other-pointer-lowtag))
+                   (do-next-filler))
+                 `((sc-case arg-fun
+                     (descriptor-reg (move lexenv arg-fun))
+                     (control-stack
+                      (loadw lexenv cfp-tn (tn-offset arg-fun))
+                      (do-next-filler))
+                     (constant
+                      (loadw lexenv code-tn (tn-offset arg-fun)
+                             other-pointer-lowtag)
+                      (do-next-filler)))
+                   (loadw function lexenv closure-fun-slot
+                    fun-pointer-lowtag)
+                   (do-next-filler)
+                   ;; The step instrumenting must be done before
+                   ;; after FUNCTION is loaded, but before ENTRY-POINT
+                   ;; is calculated.
+                   (insert-step-instrumenting function)
+                   (inst addi entry-point function
+                    (- (ash simple-fun-code-offset word-shift)
+                     fun-pointer-lowtag))
+                   ))
+           (loop
+             (if filler
+                 (do-next-filler)
+                 (return)))
+
+           (note-this-location vop :call-site)
+           (inst mtctr entry-point)
+           ;; this following line is questionable.  or else the alpha
+           ;; code (which doesn't do it) is questionable
+           ;; (inst mr code-tn function)
+           (inst bctr))
+
+         ,@(ecase return
+             (:fixed
+              '((emit-return-pc lra-label)
+                (default-unknown-values vop values nvals move-temp
+                                        temp lra-label)
+                (when cur-nfp
+                  (load-stack-tn cur-nfp nfp-save))))
+             (:unknown
+              '((emit-return-pc lra-label)
+                (note-this-location vop :unknown-return)
+                (receive-unknown-values values-start nvals start count
+                                        lra-label temp)
+                (when cur-nfp
+                  (load-stack-tn cur-nfp nfp-save))))
+             (:tail)))
        (trace-table-entry trace-table-normal))))
 
 
@@ -811,7 +880,6 @@ default-value-8
 (define-full-call call-variable nil :fixed t)
 (define-full-call multiple-call-variable nil :unknown t)
 
-
 ;;; Defined separately, since needs special code that BLT's the
 ;;; arguments down.
 (define-vop (tail-call-variable)
@@ -820,58 +888,54 @@ default-value-8
    (function-arg :scs (descriptor-reg) :target lexenv)
    (old-fp-arg :scs (any-reg) :target old-fp)
    (lra-arg :scs (descriptor-reg) :target lra))
-
   (:temporary (:sc any-reg :offset nl0-offset :from (:argument 0)) args)
   (:temporary (:sc any-reg :offset lexenv-offset :from (:argument 1)) lexenv)
   (:temporary (:sc any-reg :offset ocfp-offset :from (:argument 2)) old-fp)
   (:temporary (:sc any-reg :offset lra-offset :from (:argument 3)) lra)
-
-
+  (:temporary (:sc any-reg) temp)
   (:vop-var vop)
-
   (:generator 75
-
     ;; Move these into the passing locations if they are not already there.
     (move args args-arg)
     (move lexenv function-arg)
     (move old-fp old-fp-arg)
     (move lra lra-arg)
-
-
     ;; Clear the number stack if anything is there.
     (let ((cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(inst addi nsp-tn cur-nfp
-	      (- (bytes-needed-for-non-descriptor-stack-frame)
-		 number-stack-displacement))))
-
-   
-    (inst ba (make-fixup 'tail-call-variable :assembly-routine))))
+        (inst addi nsp-tn cur-nfp
+              (- (bytes-needed-for-non-descriptor-stack-frame)
+                 number-stack-displacement))))
+    (inst lr temp (make-fixup 'tail-call-variable :assembly-routine))
+    (inst mtlr temp)
+    (inst blr)))
 
 
 ;;;; Unknown values return:
 
 ;;; Return a single value using the unknown-values convention.
 (define-vop (return-single)
-  (:args (old-fp :scs (any-reg))
-	 (return-pc :scs (descriptor-reg))
-	 (value))
+  (:args (old-fp :scs (any-reg) :to :eval)
+         (return-pc :scs (descriptor-reg) :target lra)
+         (value))
   (:ignore value)
+  (:temporary (:sc descriptor-reg :offset lra-offset :from (:argument 1)) lra)
   (:temporary (:scs (interior-reg)) lip)
   (:vop-var vop)
   (:generator 6
     (trace-table-entry trace-table-fun-epilogue)
+    (move lra return-pc)
     ;; Clear the number stack.
     (let ((cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(inst addi nsp-tn cur-nfp
-	      (- (bytes-needed-for-non-descriptor-stack-frame)
-		 number-stack-displacement))))
+        (inst addi nsp-tn cur-nfp
+              (- (bytes-needed-for-non-descriptor-stack-frame)
+                 number-stack-displacement))))
     ;; Clear the control stack, and restore the frame pointer.
     (move csp-tn cfp-tn)
     (move cfp-tn old-fp)
     ;; Out of here.
-    (lisp-return return-pc lip :offset 2)
+    (lisp-return lra lip :offset 2)
     (trace-table-entry trace-table-normal)))
 
 ;;; Do unknown-values return of a fixed number of values.  The Values are
@@ -889,7 +953,7 @@ default-value-8
 (define-vop (return)
   (:args
    (old-fp :scs (any-reg))
-   (return-pc :scs (descriptor-reg) :to (:eval 1))
+   (return-pc :scs (descriptor-reg) :to (:eval 1) :target lra)
    (values :more t))
   (:ignore values)
   (:info nvals)
@@ -897,38 +961,40 @@ default-value-8
   (:temporary (:sc descriptor-reg :offset a1-offset :from (:eval 0)) a1)
   (:temporary (:sc descriptor-reg :offset a2-offset :from (:eval 0)) a2)
   (:temporary (:sc descriptor-reg :offset a3-offset :from (:eval 0)) a3)
+  (:temporary (:sc descriptor-reg :offset lra-offset :from (:eval 1)) lra)
   (:temporary (:sc any-reg :offset nargs-offset) nargs)
   (:temporary (:sc any-reg :offset ocfp-offset) val-ptr)
   (:temporary (:scs (interior-reg)) lip)
   (:vop-var vop)
   (:generator 6
     (trace-table-entry trace-table-fun-epilogue)
+    (move lra return-pc)
     ;; Clear the number stack.
     (let ((cur-nfp (current-nfp-tn vop)))
       (when cur-nfp
-	(inst addi nsp-tn cur-nfp
-	      (- (bytes-needed-for-non-descriptor-stack-frame)
-		 number-stack-displacement))))
+        (inst addi nsp-tn cur-nfp
+              (- (bytes-needed-for-non-descriptor-stack-frame)
+                 number-stack-displacement))))
     (cond ((= nvals 1)
-	   ;; Clear the control stack, and restore the frame pointer.
-	   (move csp-tn cfp-tn)
-	   (move cfp-tn old-fp)
-	   ;; Out of here.
-	   (lisp-return return-pc lip :offset 2))
-	  (t
-	   ;; Establish the values pointer and values count.
-	   (move val-ptr cfp-tn)
-	   (inst lr nargs (fixnumize nvals))
-	   ;; restore the frame pointer and clear as much of the control
-	   ;; stack as possible.
-	   (move cfp-tn old-fp)
-	   (inst addi csp-tn val-ptr (* nvals n-word-bytes))
-	   ;; pre-default any argument register that need it.
-	   (when (< nvals register-arg-count)
-	     (dolist (reg (subseq (list a0 a1 a2 a3) nvals))
-	       (move reg null-tn)))
-	   ;; And away we go.
-	   (lisp-return return-pc lip)))
+           ;; Clear the control stack, and restore the frame pointer.
+           (move csp-tn cfp-tn)
+           (move cfp-tn old-fp)
+           ;; Out of here.
+           (lisp-return lra lip :offset 2))
+          (t
+           ;; Establish the values pointer and values count.
+           (move val-ptr cfp-tn)
+           (inst lr nargs (fixnumize nvals))
+           ;; restore the frame pointer and clear as much of the control
+           ;; stack as possible.
+           (move cfp-tn old-fp)
+           (inst addi csp-tn val-ptr (* nvals n-word-bytes))
+           ;; pre-default any argument register that need it.
+           (when (< nvals register-arg-count)
+             (dolist (reg (subseq (list a0 a1 a2 a3) nvals))
+               (move reg null-tn)))
+           ;; And away we go.
+           (lisp-return lra lip)))
     (trace-table-entry trace-table-normal)))
 
 ;;; Do unknown-values return of an arbitrary number of values (passed
@@ -942,44 +1008,40 @@ default-value-8
    (lra-arg :scs (descriptor-reg) :to (:eval 1))
    (vals-arg :scs (any-reg) :target vals)
    (nvals-arg :scs (any-reg) :target nvals))
-
   (:temporary (:sc any-reg :offset nl1-offset :from (:argument 0)) old-fp)
   (:temporary (:sc descriptor-reg :offset lra-offset :from (:argument 1)) lra)
   (:temporary (:sc any-reg :offset nl0-offset :from (:argument 2)) vals)
   (:temporary (:sc any-reg :offset nargs-offset :from (:argument 3)) nvals)
   (:temporary (:sc descriptor-reg :offset a0-offset) a0)
   (:temporary (:scs (interior-reg)) lip)
-
-
+  (:temporary (:sc any-reg) temp)
   (:vop-var vop)
-
   (:generator 13
     (trace-table-entry trace-table-fun-epilogue)
+    (move lra lra-arg)
     (let ((not-single (gen-label)))
       ;; Clear the number stack.
       (let ((cur-nfp (current-nfp-tn vop)))
-	(when cur-nfp
-	  (inst addi nsp-tn cur-nfp
-		(- (bytes-needed-for-non-descriptor-stack-frame)
-		   number-stack-displacement))))
-
+        (when cur-nfp
+          (inst addi nsp-tn cur-nfp
+                (- (bytes-needed-for-non-descriptor-stack-frame)
+                   number-stack-displacement))))
       ;; Check for the single case.
       (inst cmpwi nvals-arg (fixnumize 1))
       (inst lwz a0 vals-arg 0)
       (inst bne not-single)
-
       ;; Return with one value.
       (move csp-tn cfp-tn)
       (move cfp-tn old-fp-arg)
       (lisp-return lra-arg lip :offset 2)
-		
       ;; Nope, not the single case.
       (emit-label not-single)
       (move old-fp old-fp-arg)
-      (move lra lra-arg)
       (move vals vals-arg)
       (move nvals nvals-arg)
-      (inst ba (make-fixup 'return-multiple :assembly-routine)))
+      (inst lr temp (make-fixup 'return-multiple :assembly-routine))
+      (inst mtlr temp)
+      (inst blr))
     (trace-table-entry trace-table-normal)))
 
 ;;;; XEP hackery:
@@ -995,8 +1057,8 @@ default-value-8
 ;;; Get the lexical environment from its passing location.
 (define-vop (setup-closure-environment)
   (:temporary (:sc descriptor-reg :offset lexenv-offset :target closure
-	       :to (:result 0))
-	      lexenv)
+               :to (:result 0))
+              lexenv)
   (:results (closure :scs (descriptor-reg)))
   (:info label)
   (:ignore label)
@@ -1005,7 +1067,7 @@ default-value-8
     (move closure lexenv)))
 
 ;;; Copy a more arg from the argument area to the end of the current frame.
-;;; Fixed is the number of non-more arguments. 
+;;; Fixed is the number of non-more arguments.
 (define-vop (copy-more-arg)
   (:temporary (:sc any-reg :offset nl0-offset) result)
   (:temporary (:sc any-reg :offset nl1-offset) count)
@@ -1015,27 +1077,27 @@ default-value-8
   (:info fixed)
   (:generator 20
     (let ((loop (gen-label))
-	  (do-regs (gen-label))
-	  (done (gen-label)))
+          (do-regs (gen-label))
+          (done (gen-label)))
       (when (< fixed register-arg-count)
-	;; Save a pointer to the results so we can fill in register args.
-	;; We don't need this if there are more fixed args than reg args.
-	(move result csp-tn))
+        ;; Save a pointer to the results so we can fill in register args.
+        ;; We don't need this if there are more fixed args than reg args.
+        (move result csp-tn))
       ;; Allocate the space on the stack.
       (cond ((zerop fixed)
-	     (inst cmpwi nargs-tn 0)
-	     (inst add csp-tn csp-tn nargs-tn)
-	     (inst beq done))
-	    (t
-	     (inst addic. count nargs-tn (- (fixnumize fixed)))
-	     (inst ble done)
-	     (inst add csp-tn csp-tn count)))
+             (inst cmpwi nargs-tn 0)
+             (inst add csp-tn csp-tn nargs-tn)
+             (inst beq done))
+            (t
+             (inst addic. count nargs-tn (- (fixnumize fixed)))
+             (inst ble done)
+             (inst add csp-tn csp-tn count)))
       (when (< fixed register-arg-count)
-	;; We must stop when we run out of stack args, not when we run out of
-	;; more args.
-	(inst addic. count nargs-tn (- (fixnumize register-arg-count)))
-	;; Everything of interest is in registers.
-	(inst ble do-regs))
+        ;; We must stop when we run out of stack args, not when we run out of
+        ;; more args.
+        (inst addic. count nargs-tn (- (fixnumize register-arg-count)))
+        ;; Everything of interest is in registers.
+        (inst ble do-regs))
       ;; Initialize dst to be end of stack.
       (move dst csp-tn)
       ;; Initialize src to be end of args.
@@ -1043,24 +1105,22 @@ default-value-8
 
       (emit-label loop)
       ;; *--dst = *--src, --count
-      (inst addi src src (- n-word-bytes))
+      (inst lwzu temp src (- n-word-bytes))
       (inst addic. count count (- (fixnumize 1)))
-      (loadw temp src)
-      (inst addi dst dst (- n-word-bytes))
-      (storew temp dst)
+      (inst stwu temp dst (- n-word-bytes))
       (inst bgt loop)
 
       (emit-label do-regs)
       (when (< fixed register-arg-count)
-	;; Now we have to deposit any more args that showed up in registers.
-	(inst subic. count nargs-tn (fixnumize fixed))
-	(do ((i fixed (1+ i)))
-	    ((>= i register-arg-count))
-	  ;; Don't deposit any more than there are.
-	  (inst beq done)
-	  (inst subic. count count (fixnumize 1))
-	  ;; Store it relative to the pointer saved at the start.
-	  (storew (nth i *register-arg-tns*) result (- i fixed))))
+        ;; Now we have to deposit any more args that showed up in registers.
+        (inst subic. count nargs-tn (fixnumize fixed))
+        (do ((i fixed (1+ i)))
+            ((>= i register-arg-count))
+          ;; Don't deposit any more than there are.
+          (inst beq done)
+          (inst subic. count count (fixnumize 1))
+          ;; Store it relative to the pointer saved at the start.
+          (storew (nth i *register-arg-tns*) result (- i fixed))))
       (emit-label done))))
 
 
@@ -1074,7 +1134,7 @@ default-value-8
 ;;; Turn more arg (context, count) into a list.
 (define-vop (listify-rest-args)
   (:args (context-arg :target context :scs (descriptor-reg))
-	 (count-arg :target count :scs (any-reg)))
+         (count-arg :target count :scs (any-reg)))
   (:arg-types * tagged-num)
   (:temporary (:scs (any-reg) :from (:argument 0)) context)
   (:temporary (:scs (any-reg) :from (:argument 1)) count)
@@ -1084,46 +1144,58 @@ default-value-8
   (:results (result :scs (descriptor-reg)))
   (:translate %listify-rest-args)
   (:policy :safe)
+  (:node-var node)
   (:generator 20
-    (move context context-arg)
-    (move count count-arg)
-    ;; Check to see if there are any arguments.
-    (inst cmpwi count 0)
-    (move result null-tn)
-    (inst beq done)
+    (let* ((enter (gen-label))
+           (loop (gen-label))
+           (done (gen-label))
+           (dx-p (node-stack-allocate-p node)))
+      (move context context-arg)
+      (move count count-arg)
+      ;; Check to see if there are any arguments.
+      (inst cmpwi count 0)
+      (move result null-tn)
+      (inst beq done)
 
     ;; We need to do this atomically.
     (pseudo-atomic (pa-flag)
-      (assemble ()
-	;; Allocate a cons (2 words) for each item.
-	(inst clrrwi result alloc-tn n-lowtag-bits)
-	(inst ori result result list-pointer-lowtag)
-	(move dst result)
-	(inst slwi temp count 1)
-	(inst add alloc-tn alloc-tn temp)
-	(inst b enter)
-
-	;; Compute the next cons and store it in the current one.
-	LOOP
-	(inst addi dst dst (* 2 n-word-bytes))
-	(storew dst dst -1 list-pointer-lowtag)
-
-	;; Grab one value.
-	ENTER
-	(loadw temp context)
-	(inst addi context context n-word-bytes)
-
-	;; Dec count, and if != zero, go back for more.
-	(inst addic. count count (- (fixnumize 1)))
-	;; Store the value into the car of the current cons (in the delay
-	;; slot).
-	(storew temp dst 0 list-pointer-lowtag)
-	(inst bgt loop)
-
-
-	;; NIL out the last cons.
-	(storew null-tn dst 1 list-pointer-lowtag)))
-    DONE))
+      ;; Allocate a cons (2 words) for each item.
+      (if dx-p
+          (progn
+            (align-csp temp)
+            (inst clrrwi result csp-tn n-lowtag-bits)
+            (inst ori result result list-pointer-lowtag)
+            (move dst result)
+            (inst slwi temp count 1)
+            (inst add csp-tn csp-tn temp))
+          (progn
+            (inst slwi temp count 1)
+            (allocation result temp list-pointer-lowtag
+                        :temp-tn dst
+                        :flag-tn pa-flag)
+            (move dst result)))
+      (inst b enter)
+
+      ;; Compute the next cons and store it in the current one.
+      (emit-label loop)
+      (inst addi dst dst (* 2 n-word-bytes))
+      (storew dst dst -1 list-pointer-lowtag)
+
+      ;; Grab one value.
+      (emit-label enter)
+      (loadw temp context)
+      (inst addi context context n-word-bytes)
+
+      ;; Dec count, and if != zero, go back for more.
+      (inst addic. count count (- (fixnumize 1)))
+      ;; Store the value into the car of the current cons (in the delay
+      ;; slot).
+      (storew temp dst 0 list-pointer-lowtag)
+      (inst bgt loop)
+
+      ;; NIL out the last cons.
+      (storew null-tn dst 1 list-pointer-lowtag))
+    (emit-label done))))
 
 
 ;;; Return the location and size of the more arg glob created by
@@ -1143,7 +1215,7 @@ default-value-8
   (:arg-types tagged-num (:constant fixnum))
   (:info fixed)
   (:results (context :scs (descriptor-reg))
-	    (count :scs (any-reg)))
+            (count :scs (any-reg)))
   (:result-types t tagged-num)
   (:note "more-arg-context")
   (:generator 5
@@ -1163,17 +1235,17 @@ default-value-8
 
 ;;; Signal various errors.
 (macrolet ((frob (name error translate &rest args)
-	     `(define-vop (,name)
-		,@(when translate
-		    `((:policy :fast-safe)
-		      (:translate ,translate)))
-		(:args ,@(mapcar #'(lambda (arg)
-				     `(,arg :scs (any-reg descriptor-reg)))
-				 args))
-		(:vop-var vop)
-		(:save-p :compute-only)
-		(:generator 1000
-		  (error-call vop ,error ,@args)))))
+             `(define-vop (,name)
+                ,@(when translate
+                    `((:policy :fast-safe)
+                      (:translate ,translate)))
+                (:args ,@(mapcar #'(lambda (arg)
+                                     `(,arg :scs (any-reg descriptor-reg)))
+                                 args))
+                (:vop-var vop)
+                (:save-p :compute-only)
+                (:generator 1000
+                  (error-call vop ',error ,@args)))))
   (frob arg-count-error invalid-arg-count-error
     sb!c::%arg-count-error nargs)
   (frob type-check-error object-not-type-error sb!c::%type-check-error
@@ -1185,3 +1257,24 @@ default-value-8
   (frob unknown-key-arg-error unknown-key-arg-error
         sb!c::%unknown-key-arg-error key)
   (frob nil-fun-returned-error nil-fun-returned-error nil fun))
+
+(define-vop (step-instrument-before-vop)
+  (:temporary (:scs (descriptor-reg)) stepping)
+  (:policy :fast-safe)
+  (:vop-var vop)
+  (:generator 3
+    ;; Get the symbol-value of SB!IMPL::*STEPPING*
+    #!-sb-thread
+    (load-symbol-value stepping sb!impl::*stepping*)
+    #!+sb-thread
+    (loadw stepping thread-base-tn thread-stepping-slot)
+    (inst cmpw stepping null-tn)
+    ;; If it's not null, trap.
+    (inst beq DONE)
+    ;; CONTEXT-PC will be pointing here when the interrupt is handled,
+    ;; not after the UNIMP.
+    (note-this-location vop :step-before-vop)
+    ;; CALLEE-REGISTER-OFFSET isn't needed for before-traps, so we
+    ;; can just use a bare SINGLE-STEP-BEFORE-TRAP as the code.
+    (inst unimp single-step-before-trap)
+    DONE))