From cd23187a89f532f7b57e88b5392a7905e6ae3276 Mon Sep 17 00:00:00 2001
From: Nikodemus Siivola <nikodemus@random-state.net>
Date: Fri, 5 Jun 2009 11:36:46 +0000
Subject: [PATCH] 1.0.29.2: implement fixnump/signed-word VOP on x86 and x86-64

 * No need to cons up a bignum, and just one branch required.
   Eliminates a whole class of signed-word to integer coercions.
---
 NEWS                               |  2 ++
 src/compiler/x86-64/type-vops.lisp | 16 ++++++++++++++++
 src/compiler/x86/type-vops.lisp    | 19 +++++++++++++++++++
 version.lisp-expr                  |  2 +-
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 3f3fe5f8d..9e4f26528 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,6 @@
 ;;;; -*- coding: utf-8; fill-column: 78 -*-
+  * optimization: more efficient type-checks for FIXNUMs when the value
+    is known to be a signed word on x86 and x86-64.
   * bug fix: on 64 bit platforms FILL worked incorrectly on arrays with
     upgraded element type (COMPLEX SINGLE-FLOAT), regression from 1.0.28.55.
     (thanks to Paul Khuong)
diff --git a/src/compiler/x86-64/type-vops.lisp b/src/compiler/x86-64/type-vops.lisp
index 1298a5e22..d8e49e0ac 100644
--- a/src/compiler/x86-64/type-vops.lisp
+++ b/src/compiler/x86-64/type-vops.lisp
@@ -190,6 +190,22 @@
     (inst mov tmp value)
     (inst shr tmp n-positive-fixnum-bits)))
 
+(define-vop (fixnump/signed-byte-64 type-predicate)
+  (:args (value :scs (signed-reg)))
+  (:info)
+  (:conditional :z)
+  (:arg-types signed-num)
+  (:translate fixnump)
+  (:generator 5
+    ;; Hackers Delight, p. 53: signed
+    ;;    a <= x <= a + 2^n - 1
+    ;; is equivalent to unsigned
+    ;;    ((x-a) >> n) = 0
+    (inst mov rax-tn #.(- sb!xc:most-negative-fixnum))
+    (inst add rax-tn value)
+    (inst shr rax-tn #.(integer-length (- sb!xc:most-positive-fixnum
+                                          sb!xc:most-negative-fixnum)))))
+
 ;;; A (SIGNED-BYTE 64) can be represented with either fixnum or a bignum with
 ;;; exactly one digit.
 
diff --git a/src/compiler/x86/type-vops.lisp b/src/compiler/x86/type-vops.lisp
index 9d53fe955..0284ae4dd 100644
--- a/src/compiler/x86/type-vops.lisp
+++ b/src/compiler/x86/type-vops.lisp
@@ -212,8 +212,27 @@
   (:arg-types unsigned-num)
   (:translate fixnump)
   (:generator 5
+    ;; We could encode this with :Z and SHR, analogously to the signed-byte-32
+    ;; case below -- as we do on x86-64 -- but that costs us an extra
+    ;; register. Compromises...
     (inst cmp value #.sb!xc:most-positive-fixnum)))
 
+(define-vop (fixnump/signed-byte-32 type-predicate)
+  (:args (value :scs (signed-reg)))
+  (:info)
+  (:conditional :z)
+  (:arg-types signed-num)
+  (:translate fixnump)
+  (:generator 5
+    ;; Hackers Delight, p. 53: signed
+    ;;    a <= x <= a + 2^n - 1
+    ;; is equivalent to unsigned
+    ;;    ((x-a) >> n) = 0
+    (inst mov eax-tn value)
+    (inst sub eax-tn #.sb!xc:most-negative-fixnum)
+    (inst shr eax-tn #.(integer-length (- sb!xc:most-positive-fixnum
+                                          sb!xc:most-negative-fixnum)))))
+
 ;;; A (SIGNED-BYTE 32) can be represented with either fixnum or a bignum with
 ;;; exactly one digit.
 
diff --git a/version.lisp-expr b/version.lisp-expr
index ed252179c..9f9e8bfaa 100644
--- a/version.lisp-expr
+++ b/version.lisp-expr
@@ -17,4 +17,4 @@
 ;;; checkins which aren't released. (And occasionally for internal
 ;;; versions, especially for internal versions off the main CVS
 ;;; branch, it gets hairier, e.g. "0.pre7.14.flaky4.13".)
-"1.0.29.1"
+"1.0.29.2"
-- 
2.11.4.GIT