Added comment on how to improve ultra sparc

performance.

Rev: src/nettle/sparc/aes.asm:1.124

diff --git a/sparc/aes.asm b/sparc/aes.asm
index 6e0f0b69c6206390e5ace66df7cf3c24236b4e2e..9fce564f473bf51dbc86865296155c70bb10baba 100644 (file)
--- a/sparc/aes.asm
+++ b/sparc/aes.asm
@@ -18,6 +18,13 @@
 ! the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 ! MA 02111-1307, USA.
 
+! FIXME: For improved ultra sparc performance, we should avoid ALU
+! instructions that use the result of an immediately preceeding ALU
+! instruction. It is also a good idea to have a greater distance than
+! one instruction between a load and use of its value, as that reduces
+! the penalty for cache misses. Such instruction sequences are marked
+! with !U comments.
+
 ! NOTE: Some of the %g registers are reserved for operating system etc
 ! (see gcc/config/sparc.h). The only %g registers that seems safe to
 ! use are %g1-%g3.
@@ -28,7 +35,7 @@
        !                       
        
        .file   "aes.asm"
-       
+
 ! Arguments
 define(ctx, %i0)
 define(T, %i1)
@@ -71,7 +78,7 @@ define(<AES_LOAD>, <
        ldub    [src+$1+2], t2
        sll     t1, 8, t1
        
-       or      t0, t1, t0      
+       or      t0, t1, t0      ! U
        ldub    [src+$1+3], t1
        sll     t2, 16, t2
        or      t0, t2, t0
@@ -98,7 +105,7 @@ define(<AES_ROUND>, <
        
        ld      [T0+t0], t0             ! 0
        sll     t1, 2, t1               ! 1
-       ld      [T1+t1], t1             ! 1
+       ld      [T1+t1], t1             ! 1 !U
        ld      [IDX3+$1], t2           ! 3
        
        xor     t0, t1, t0              ! 0, 1
@@ -107,15 +114,15 @@ define(<AES_ROUND>, <
        ldub    [wtxt+t2], t2           ! 3
        sll     t1, 2, t1               ! 2
        
-       ld      [T2+t1], t1             ! 2
+       ld      [T2+t1], t1             ! 2     !U
        sll     t2, 2, t2               ! 3
-       ld      [T3+t2], t2             ! 3
+       ld      [T3+t2], t2             ! 3     !U
        xor     t0, t1, t0              ! 0, 1, 2
        
        ! Fetch roundkey
        ld      [key + $1], t1
        xor     t0, t2, t0              ! 0, 1, 2, 3
-       xor     t0, t1, t0
+       xor     t0, t1, t0              !U
        st      t0, [tmp + $1]>)dnl
 
 C AES_FINAL_ROUND(i)
@@ -133,7 +140,7 @@ define(<AES_FINAL_ROUND>, <
        ldub    [T+t1], t1              ! 1
        ld      [IDX3 + $1], t2         ! 3
        sll     t1, 8, t1               ! 1
-       or      t0, t1, t0              ! 0, 1
+       or      t0, t1, t0              ! 0, 1 !U
        
        ! IDX2(j) = j XOR 2
        ldub    [wtxt+eval($1 ^ 8)+1], t1       ! 2
@@ -142,19 +149,19 @@ define(<AES_FINAL_ROUND>, <
        ldub    [T+t2], t2              ! 3
        
        sll     t1, 16, t1              ! 2
-       or      t0, t1, t0              ! 0, 1, 2
+       or      t0, t1, t0              ! 0, 1, 2 !U
        sll     t2, 24, t2              ! 3
        ld      [key + $1], t1
        
        or      t0, t2, t0              ! 0, 1, 2, 3
-       xor     t0, t1, t0
-       srl     t0, 24, t1
-       stb     t1, [dst+$1+3]
+       xor     t0, t1, t0              !U
+       srl     t0, 24, t1              !U
+       stb     t1, [dst+$1+3]          !U
        
        srl     t0, 16, t1
-       stb     t1, [dst+$1+2]
+       stb     t1, [dst+$1+2]          !U
        srl     t0, 8, t1
-       stb     t1, [dst+$1+1]
+       stb     t1, [dst+$1+1]          !U
        
        stb     t0, [dst+$1]>)dnl