rc4-586.pl: optimize unused code path.

diff --git a/crypto/rc4/asm/rc4-586.pl b/crypto/rc4/asm/rc4-586.pl
index 116abb5b78e6cb2d5096386aa7900732af0eaabf..0c4cac4e8986e24970ca04fe381526a1b2df1444 100644 (file)
--- a/crypto/rc4/asm/rc4-586.pl
+++ b/crypto/rc4/asm/rc4-586.pl
@@ -30,8 +30,8 @@
 
 # May 2011
 #
-# Optimize for Core2 and Westmere [and Opteron]. Current performance
-# in cycles per processed byte (less is better) is:
+# Optimize for Core2 and Westmere [and incidentally Opteron]. Current
+# performance in cycles per processed byte (less is better) is:
 #
 # Pentium      10.2                    # original numbers
 # Pentium III  7.8(*)
@@ -43,11 +43,12 @@
 # Sandy Bridge 5.4/0%
 #
 # (*)  PIII can actually deliver 6.6 cycles per byte with MMX code,
-#      but this specific code performs poorly on Core2. While below
-#      MMX code delivering 5.8 on Core2 performs at 8.0 on PIII:-(
-#      As PIII is not a "hot" CPU [anymore], I chose not to introduce
-#      PIII-specific code path, which is why MMX code path is quarded
-#      by SSE2 bit (see below), not MMX.
+#      but this specific code performs poorly on Core2. And vice
+#      versa, below MMX/SSE code delivering 5.8/7.1 on Core2 performs
+#      poorly on PIII, at 8.0/14.5:-( As PIII is not a "hot" CPU
+#      [anymore], I chose to discard PIII-specific code path and opt
+#      for original IALU-only code, which is why MMX/SSE code path
+#      is guarded by SSE2 bit (see below), not MMX/SSE.
 # (**) Performance vs. block size on Core2 and Westmere had a maximum
 #      at ... 64 bytes block size. And it was quite a maximum, 40-60%
 #      in comparison to largest 8KB block size. Above improvement
@@ -88,31 +89,40 @@ sub RC4_loop {
 }
 
 if ($alt=0) {
-  # works ~5% faster on Atom and ~20% slower on Core2
+  # >20% faster on Atom and Sandy Bridge[!], 8% faster on Opteron,
+  # but ~40% slower on Core2 and Westmere... Attempt to add movz
+  # brings down Opteron by 25%, Atom and Sandy Bridge by 15%, yet
+  # on Core2 with movz it's almost 20% slower than below alternative
+  # code... Yes, it's a total mess...
   my @XX=($xx,$out);
-  $RC4_loop_mmx = sub {
+  $RC4_loop_mmx = sub {                # SSE actually...
     my $i=shift;
+    my $j=$i<=0?0:$i>>1;
+    my $mm=$i<=0?"mm0":"mm".($i&1);
 
-       &add    ($yy,$tx);
-       &movz   ($yy,&LB($yy));
+       &add    (&LB($yy),&LB($tx));
        &lea    (@XX[1],&DWP(1,@XX[0]));
-       &psllq  ("mm1",8*(($i-1)&7))                    if (abs($i)!=1);
+       &pxor   ("mm2","mm0")                           if ($i==0);
+       &psllq  ("mm1",8)                               if ($i==0);
        &and    (@XX[1],0xff);
+       &pxor   ("mm0","mm0")                           if ($i<=0);
        &mov    ($ty,&DWP(0,$dat,$yy,4));
        &mov    (&DWP(0,$dat,$yy,4),$tx);
+       &pxor   ("mm1","mm2")                           if ($i==0);
        &mov    (&DWP(0,$dat,$XX[0],4),$ty);
-       &add    ($ty,$tx);
+       &add    (&LB($ty),&LB($tx));
        &movd   (@XX[0],"mm7")                          if ($i==0);
-       &movz   ($ty,&LB($ty));
        &mov    ($tx,&DWP(0,$dat,@XX[1],4));
-       &pxor   ("mm2",$i==1?"mm0":"mm1")               if ($i>=0);
-       &movq   ("mm0",&QWP(0,$inp))                    if ($i<=0);
-       &movq   (&QWP(-8,(@XX[0],$inp)),"mm2")          if ($i==0);
-       &movd   ($i>0?"mm1":"mm2",&DWP(0,$dat,$ty,4));
+       &pxor   ("mm1","mm1")                           if ($i==1);
+       &movq   ("mm2",&QWP(0,$inp))                    if ($i==1);
+       &movq   (&QWP(-8,(@XX[0],$inp)),"mm1")          if ($i==0);
+       &pinsrw ($mm,&DWP(0,$dat,$ty,4),$j);
 
        push    (@XX,shift(@XX))                        if ($i>=0);
   }
 } else {
+  # Using pinsrw here improves performane on Intel CPUs by 2-3%, but
+  # brings down AMD by 7%...
   $RC4_loop_mmx = sub {
     my $i=shift;
 
@@ -185,8 +195,6 @@ if ($alt=0) {
        &movd   ("mm7",&wparam(3))      if ($alt);
        &and    ($ty,-8);
        &lea    ($ty,&DWP(-8,$inp,$ty));
-       &mov    (&wparam(2),$ty);
-
        &mov    (&DWP(-4,$dat),$ty);    # save input+(len/8)*8-8
 
        &$RC4_loop_mmx(-1);
@@ -200,10 +208,17 @@ if ($alt=0) {
                &lea    ($inp,&DWP(8,$inp));
        &jb     (&label("loop_mmx"));
 
-       &movd   ($out,"mm7")            if ($alt);
+    if ($alt) {
+       &movd   ($out,"mm7");
+       &pxor   ("mm2","mm0");
+       &psllq  ("mm1",8);
+       &pxor   ("mm1","mm2");
+       &movq   (&QWP(-8,$out,$inp),"mm1");
+    } else {
        &psllq  ("mm1",56);
        &pxor   ("mm2","mm1");
        &movq   (&QWP(-8,$out,$inp),"mm2");
+    }
        &emms   ();
 
        &cmp    ($inp,&wparam(1));      # compare to input+len
@@ -267,7 +282,7 @@ if ($alt=0) {
 
 &set_label("done");
        &dec    (&LB($xx));
-       &mov    (&BP(-4,$dat),&LB($yy));        # save key->y
+       &mov    (&DWP(-4,$dat),$yy);            # save key->y
        &mov    (&BP(-8,$dat),&LB($xx));        # save key->x
 &set_label("abort");
 &function_end("RC4");