[Sbcl-commits] CVS: sbcl/src/compiler/x86-64 insts.lisp, 1.28, 1.29 system.lisp, 1.8, 1.9

[Nikodemus S. <de...@us...>]

Update of /cvsroot/sbcl/sbcl/src/compiler/x86-64
In directory sc8-pr-cvs8.sourceforge.net:/tmp/cvs-serv14783/src/compiler/x86-64

Modified Files:
	insts.lisp system.lisp 
Log Message:
1.0.15.33: implement SB-VM::WITH-CYCLE-COUNTER for x86 and x86-64

 * For potential future exporting from SB-SYS.

 * Thanks to Paul Khuong and the CMUCL team.


Index: insts.lisp
===================================================================
RCS file: /cvsroot/sbcl/sbcl/src/compiler/x86-64/insts.lisp,v
retrieving revision 1.28
retrieving revision 1.29
diff -u -d -r1.28 -r1.29
--- insts.lisp	5 Mar 2008 01:48:07 -0000	1.28
+++ insts.lisp	14 Mar 2008 20:10:18 -0000	1.29
@@ -542,6 +542,10 @@
   (accum :type 'accum)
   (imm))
 
+(sb!disassem:define-instruction-format (two-bytes 16
+                                        :default-printer '(:name))
+  (op :fields (list (byte 8 0) (byte 8 8))))
+
 ;;; A one-byte instruction with a #x66 prefix, used to indicate an
 ;;; operand size of :word.
 (sb!disassem:define-instruction-format (x66-byte 16
@@ -2967,3 +2971,17 @@
    (emit-byte segment #x0f)
    (emit-byte segment #xae)
    (emit-ea segment dst 3)))
+
+;;;; Miscellany
+
+(define-instruction cpuid (segment)
+  (:printer two-bytes ((op '(#b00001111 #b10100010))))
+  (:emitter
+   (emit-byte segment #b00001111)
+   (emit-byte segment #b10100010)))
+
+(define-instruction rdtsc (segment)
+  (:printer two-bytes ((op '(#b00001111 #b00110001))))
+  (:emitter
+   (emit-byte segment #b00001111)
+   (emit-byte segment #b00110001)))

Index: system.lisp
===================================================================
RCS file: /cvsroot/sbcl/sbcl/src/compiler/x86-64/system.lisp,v
retrieving revision 1.8
retrieving revision 1.9
diff -u -d -r1.8 -r1.9
--- system.lisp	14 Feb 2008 16:40:47 -0000	1.8
+++ system.lisp	14 Mar 2008 20:10:18 -0000	1.9
@@ -290,7 +290,70 @@
     (note-next-instruction vop :internal-error)
     (inst wait)))
 
-;;;; dynamic vop count collection support
+;;;; Miscellany
+
+;;; the RDTSC instruction (present on Pentium processors and
+;;; successors) allows you to access the time-stamp counter, a 64-bit
+;;; model-specific register that counts executed cycles. The
+;;; instruction returns the low cycle count in EAX and high cycle
+;;; count in EDX.
+;;;
+;;; In order to obtain more significant results on out-of-order
+;;; processors (such as the Pentium II and later), we issue a
+;;; serializing CPUID instruction before and after reading the cycle
+;;; counter. This instruction is used for its side effect of emptying
+;;; the processor pipeline, to ensure that the RDTSC instruction is
+;;; executed once all pending instructions have been completed and
+;;; before any others. CPUID writes to EBX and ECX in addition to EAX
+;;; and EDX, so they need to be added as temporaries.
+;;;
+;;; Note that cache effects mean that the cycle count can vary for
+;;; different executions of the same code (it counts cycles, not
+;;; retired instructions). Furthermore, the results are per-processor
+;;; and not per-process, so are unreliable on multiprocessor machines
+;;; where processes can migrate between processors.
+;;;
+;;; This method of obtaining a cycle count has the advantage of being
+;;; very fast (around 20 cycles), and of not requiring a system call.
+;;; However, you need to know your processor's clock speed to translate
+;;; this into real execution time.
+;;;
+;;; FIXME: This about the WITH-CYCLE-COUNTER interface a bit, and then
+;;; perhaps export it from SB-SYS.
+
+(defknown %read-cycle-counter () (values (unsigned-byte 32) (unsigned-byte 32)) ())
+
+(define-vop (%read-cycle-counter)
+  (:policy :fast-safe)
+  (:translate %read-cycle-counter)
+  (:temporary (:sc unsigned-reg :offset eax-offset :target lo) eax)
+  (:temporary (:sc unsigned-reg :offset edx-offset :target hi) edx)
+  (:temporary (:sc unsigned-reg :offset ebx-offset) ebx)
+  (:temporary (:sc unsigned-reg :offset ecx-offset) ecx)
+  (:ignore ebx ecx)
+  (:results (hi :scs (unsigned-reg))
+            (lo :scs (unsigned-reg)))
+  (:result-types unsigned-num unsigned-num)
+  (:generator 5
+     (zeroize eax)
+     (inst cpuid)
+     (inst rdtsc)
+     (inst push edx)
+     (inst push eax)
+     (zeroize eax)
+     (inst cpuid)
+     (inst pop lo)
+     (inst pop hi)))
+
+(defmacro with-cycle-counter (&body body)
+  "Returns the primary value of BODY as the primary value, and the
+number of CPU cycles elapsed as secondary value. EXPERIMENTAL."
+  (with-unique-names (hi0 hi1 lo0 lo1)
+    `(multiple-value-bind (,hi0 ,lo0) (%read-cycle-counter)
+       (values (locally ,@body)
+               (multiple-value-bind (,hi1 ,lo1) (%read-cycle-counter)
+                 (+ (ash (- ,hi1 ,hi0) 32)
+                    (- ,lo1 ,lo0)))))))
 
 #!+sb-dyncount
 (define-vop (count-me)