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[patch][rfa] Don't Generate Code to Support Unused Write Stacks


Hi,

This patch is for cgen generating SID only.

When generating write stacks and the supporting code in order to suppor the (delay ...) rtl construct for SID, cgen currently generates a write stack for all registers and memory modes regardless of whether they are used or not. This is a performance problem uding writeback as the majority of the generated stacks are never written to. For most ports using (delay ...), the pc and perhaps one or two additional items are all that are ever delayed.

This patch keeps track of which hardware and memory modes are actually used by (delay ...) and generates only the needed write stacks. One potentially icky part of the patch is that it requires that semantics be generated first, since this is where the usage information is gathered. I modified sid/component/cgen-cpu/CGEN.sh.in to ensure this.

For the internal port for which performance was an issue, this yielded an improvement of 17%. I have also tested this on mt and m32r, the two other ports currently using write stacks.

Comments? Concerns? OK to commit?

Dave
2006-07-11  Dave Brolley  <brolley@redhat.com>

	* CGEN.sh.in (fileopts): Place semantic switches first so that they
	are processed first.

2006-07-11  Dave Brolley  <brolley@redhat.com>

	* cpu/sh64-compact.cpu (movual, movual2): New insns.
	(movcol): New insn.
	* cpu/sh.cpu (sh4a-nofpu-models): New pmacro.
	* sid.scm (-op-gen-delayed-set-maybe-trace): If delay used, mote the
	hardware or memory mode which was used.
	* sid-cpu.scm (hw-need-write-stack?): New function.
	(-gen-hw-stream-and-destream-fns): Compute stack-regs. Use it to
	identify hardware which uses write stacks.
	(useful-mode-names): Renamed to write-stack-memory-mode-names.
	Initialized to an empty list.
	(-gen-writestacks, -gen-reset-fn, -gen-unified-write-fn): Use
	hw-need-write-stack?.
	* hardware.scm (used-in-delay-rtl?): New member of <hardware-base>.
	(define-getters <hardware-base>): Define used-in-delay-rtl?.
	(used-in-delay-rtl?): New method of <hardware-base>.
	(hw-used-in-delay-rtl?): New function.

Index: cgen/hardware.scm
===================================================================
RCS file: /cvs/cvsfiles/devo/cgen/hardware.scm,v
retrieving revision 1.49
diff -c -p -r1.49 hardware.scm
*** cgen/hardware.scm	20 Jul 2003 18:06:02 -0000	1.49
--- cgen/hardware.scm	12 Jul 2006 19:23:43 -0000
***************
*** 66,71 ****
--- 66,75 ----
  		; or #f if not computed yet.
  		; This is a derived from the ISA attribute and is for speed.
  		(isas-cache . #f)
+ 
+ 		; Flag indicates whether this hw has been used in a (delay ...)
+ 		; rtl expression
+ 		(used-in-delay-rtl? . #f)
  		)
  	      nil)
  )
***************
*** 77,83 ****
     ; ??? These might be more properly named hw-get/hw-set, but those names
     ; seem ambiguous.
     (get . getter) (set . setter)
!    isas-cache)
  )
  
  ; Mode,rank,shape support.
--- 81,87 ----
     ; ??? These might be more properly named hw-get/hw-set, but those names
     ; seem ambiguous.
     (get . getter) (set . setter)
!    isas-cache used-in-delay-rtl?)
  )
  
  ; Mode,rank,shape support.
***************
*** 159,164 ****
--- 163,177 ----
  )
  
  (define (hw-isas hw) (send hw 'get-isas))
+ 
+ ; Was this hardware used in a (delay ...) rtl expression?
+ 
+ (method-make!
+  <hardware-base> 'used-in-delay-rtl?
+  (lambda (self) (elm-get self 'used-in-delay-rtl?))
+ )
+ 
+ (define (hw-used-in-delay-rtl? hw) (send hw 'used-in-delay-rtl?))
  
  ; FIXME: replace pc?,memory?,register?,iaddress? with just one method.
  
Index: cgen/sid-cpu.scm
===================================================================
RCS file: /cvs/cvsfiles/devo/cgen/sid-cpu.scm,v
retrieving revision 1.65
diff -c -p -r1.65 sid-cpu.scm
*** cgen/sid-cpu.scm	18 Jun 2006 17:00:04 -0000	1.65
--- cgen/sid-cpu.scm	12 Jul 2006 19:23:44 -0000
*************** namespace @arch@ {
*** 171,176 ****
--- 171,180 ----
         (not (obj-has-attr? hw 'VIRTUAL)))
  )
  
+ (define (hw-need-write-stack? hw)
+   (and (register? hw) (hw-used-in-delay-rtl? hw))
+ )
+ 
  ; Subroutine of -gen-hardware-types to generate the struct containing
  ; hardware elements of one isa.
  
*************** namespace @arch@ {
*** 204,209 ****
--- 208,214 ----
  (define (-gen-hw-stream-and-destream-fns) 
    (let* ((sa string-append)
  	 (regs (find hw-need-storage? (current-hw-list)))
+ 	 (stack-regs (find hw-need-write-stack? (current-hw-list)))
  	 (reg-dim (lambda (r) 
  		    (let ((dims (-hw-vector-dims r)))
  		      (if (equal? 0 (length dims)) 
*************** namespace @arch@ {
*** 211,219 ****
  			  (number->string (car dims))))))
  	 (write-stacks 
  	  (map (lambda (n) (sa n "_writes"))
! 	       (append (map (lambda (r) (gen-c-symbol (obj:name r))) regs)
  		       ;; %redact changeone /sa m/ /sa \(symbol-\>string m\)/ unless renesas-sh-optimizations
! 		       (map (lambda (m) (sa m "_memory")) useful-mode-names))))
  	 (stream-reg (lambda (r) 
  		       (let ((rname (sa "hardware." (gen-c-symbol (obj:name r)))))
  			 (if (hw-scalar? r)
--- 216,224 ----
  			  (number->string (car dims))))))
  	 (write-stacks 
  	  (map (lambda (n) (sa n "_writes"))
! 	       (append (map (lambda (r) (gen-c-symbol (obj:name r))) stack-regs)
  		       ;; %redact changeone /sa m/ /sa \(symbol-\>string m\)/ unless renesas-sh-optimizations
! 		       (map (lambda (m) (sa m "_memory")) write-stack-memory-mode-names))))
  	 (stream-reg (lambda (r) 
  		       (let ((rname (sa "hardware." (gen-c-symbol (obj:name r)))))
  			 (if (hw-scalar? r)
*************** typedef struct {
*** 382,388 ****
  ;;; begin stack-based write schedule
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  
! (define useful-mode-names '(BI QI HI SI DI UQI UHI USI UDI SF DF))
  
  (define (-calculated-memory-write-buffer-size)
    (let* ((is-mem? (lambda (op) (eq? (hw-sem-name (op:type op)) 'h-memory)))
--- 387,393 ----
  ;;; begin stack-based write schedule
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  
! (define write-stack-memory-mode-names '())
  
  (define (-calculated-memory-write-buffer-size)
    (let* ((is-mem? (lambda (op) (eq? (hw-sem-name (op:type op)) 'h-memory)))
*************** typedef struct {
*** 447,454 ****
  
  
  (define (-gen-writestacks)
!   (let* ((hw (find register? (current-hw-list)))
! 	 (modes useful-mode-names) 
  	 (hw-pairs (map (lambda (h) (list (gen-c-symbol (obj:name h))
  					    (obj:name (hw-mode h)))) 
  			hw))
--- 452,459 ----
  
  
  (define (-gen-writestacks)
!   (let* ((hw (find hw-need-write-stack? (current-hw-list)))
! 	 (modes write-stack-memory-mode-names) 
  	 (hw-pairs (map (lambda (h) (list (gen-c-symbol (obj:name h))
  					    (obj:name (hw-mode h)))) 
  			hw))
*************** using namespace cgen;
*** 629,637 ****
  (define (-gen-reset-fn)
    (let* ((sa string-append)
  	 (objs (append (map (lambda (h) (gen-c-symbol (obj:name h))) 
! 			    (find register? (current-hw-list)))
  		       (map (lambda (m) (sa (symbol->string m) "_memory"))
! 			    useful-mode-names)))
  	 (clr (lambda (elt) (sa "    clear_stacks (" elt "_writes);\n"))))
      (sa 
       "  template <typename ST> \n"
--- 634,642 ----
  (define (-gen-reset-fn)
    (let* ((sa string-append)
  	 (objs (append (map (lambda (h) (gen-c-symbol (obj:name h))) 
! 			    (find hw-need-write-stack? (current-hw-list)))
  		       (map (lambda (m) (sa (symbol->string m) "_memory"))
! 			    write-stack-memory-mode-names)))
  	 (clr (lambda (elt) (sa "    clear_stacks (" elt "_writes);\n"))))
      (sa 
       "  template <typename ST> \n"
*************** using namespace cgen;
*** 645,652 ****
       "  }")))
  
  (define (-gen-unified-write-fn) 
!   (let* ((hw (find register? (current-hw-list)))
! 	 (modes useful-mode-names)	
  	 (hw-triples (map (lambda (h) (list (gen-c-symbol (obj:name h))
  					    (obj:name (hw-mode h))
  					    (length (-hw-vector-dims h)))) 
--- 650,657 ----
       "  }")))
  
  (define (-gen-unified-write-fn) 
!   (let* ((hw (find hw-need-write-stack? (current-hw-list)))
! 	 (modes write-stack-memory-mode-names)	
  	 (hw-triples (map (lambda (h) (list (gen-c-symbol (obj:name h))
  					    (obj:name (hw-mode h))
  					    (length (-hw-vector-dims h)))) 
Index: cgen/sid.scm
===================================================================
RCS file: /cvs/cvsfiles/devo/cgen/sid.scm,v
retrieving revision 1.64
diff -c -p -r1.64 sid.scm
*** cgen/sid.scm	20 Jun 2006 19:54:18 -0000	1.64
--- cgen/sid.scm	12 Jul 2006 19:23:44 -0000
***************
*** 1100,1105 ****
--- 1100,1110 ----
  	 (idx-args (if (equal? idx "") "" (string-append ", " idx)))
  	 )
      
+     (if delayval
+ 	(if (eq? (obj:name hw) 'h-memory)
+ 	    (set write-stack-memory-mode-names (cons md write-stack-memory-mode-names))
+ 	    (elm-set! hw 'used-in-delay-rtl? #t)))
+ 
      (string-append
       "  {\n"
  
Index: sid/component/cgen-cpu/CGEN.sh.in
===================================================================
RCS file: /cvs/cvsfiles/devo/sid/component/cgen-cpu/CGEN.sh.in,v
retrieving revision 1.10
diff -c -p -r1.10 CGEN.sh.in
*** sid/component/cgen-cpu/CGEN.sh.in	10 May 2006 20:44:49 -0000	1.10
--- sid/component/cgen-cpu/CGEN.sh.in	12 Jul 2006 19:24:52 -0000
*************** rm -f tmp-semsw-$$.cxx1 tmp-semsw-$$.cxx
*** 78,83 ****
--- 78,85 ----
  rm -f tmp-dec-$$.h1 tmp-dec-$$.h
  rm -f tmp-dec-$$.cxx1 tmp-dec-$$.cxx
  
+ # Do semantics first, if specified because some information is collected
+ # about write stacks during this pass which is used by other passes.
  fileopts=""
  for f in $filespecs
  do
*************** do
*** 89,96 ****
      decode.cxx) fileopts="$fileopts -D tmp-dec-$$.cxx1" ;;
      model.h) fileopts="$fileopts -N tmp-mod-$$.h1" ;;
      model.cxx) fileopts="$fileopts -M tmp-mod-$$.cxx1" ;;
!     semantics.cxx) fileopts="$fileopts -S tmp-sem-$$.cxx1" ;;
!     sem-switch.cxx) fileopts="$fileopts -X tmp-semsw-$$.cxx1" ;;
      write.cxx) fileopts="$fileopts -W tmp-write-$$.cxx1" ;;
      *) echo "unknown file spec: $f" >&2 ; exit 1 ;;
      esac
--- 91,98 ----
      decode.cxx) fileopts="$fileopts -D tmp-dec-$$.cxx1" ;;
      model.h) fileopts="$fileopts -N tmp-mod-$$.h1" ;;
      model.cxx) fileopts="$fileopts -M tmp-mod-$$.cxx1" ;;
!     semantics.cxx) fileopts="-S tmp-sem-$$.cxx1 $fileopts" ;;
!     sem-switch.cxx) fileopts="-X tmp-semsw-$$.cxx1 $fileopts" ;;
      write.cxx) fileopts="$fileopts -W tmp-write-$$.cxx1" ;;
      *) echo "unknown file spec: $f" >&2 ; exit 1 ;;
      esac

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