xnu-792.6.70.tar.gz

[apple/xnu.git] / libkern / i386 / OSAtomic.s

diff --git a/libkern/i386/OSAtomic.s b/libkern/i386/OSAtomic.s
index e7f13bf558a62f459cf1d6336d78b2d1277c4d1d..68b10523efdeb1a1f5660aa2d226ca87eb4733c9 100644 (file)
--- a/libkern/i386/OSAtomic.s
+++ b/libkern/i386/OSAtomic.s
@@ -27,22 +27,11 @@
        .globl _OSCompareAndSwap
 
 _OSCompareAndSwap:
-       #; this is _lame_, the project will not currently accept asm code that
-       #; requires anything beyond a 386, but that chip:
-       #; - does not support MP
-       #; - does not support the cmpxchgl instruction
-       #; - does not support the lock meta-instruction
-       #; so what is a poor guy to do?  comment it out...
-       pushl           %edi
-       pushl           %esi
-       movl            0+8+4(%esp),%eax        #; oldValue
-       movl            4+8+4(%esp),%edi        #; newValue
-       movl            8+8+4(%esp),%esi        #; ptr
+       movl             4(%esp), %eax  #; oldValue
+       movl             8(%esp), %edx  #; newValue
+       movl            12(%esp), %ecx  #; ptr
        lock
-       cmpxchgl        %edi,0(%esi)            #; CAS (eax is an implicit operand)
-       sete            %al                                     #; did CAS succeed? (TZ=1)
-       andl            $0x000000ff,%eax        #; clear out the high bytes (has to be an easier way...)
-       popl            %esi
-       popl            %edi
+       cmpxchgl        %edx, 0(%ecx)   #; CAS (eax is an implicit operand)
+       sete            %al                             #; did CAS succeed? (TZ=1)
+       movzbl          %al, %eax               #; clear out the high bytes
        ret
-