From: Andy Polyakov <appro@openssl.org>
Date: Wed, 26 May 2010 21:36:36 +0000 (+0000)
Subject: gcm128.c: P.-M. Hager has tipped about possibility to fold reductions
X-Git-Tag: OpenSSL-fips-2_0-rc1~1087
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e747f4d41885efa200b8fafa67cd81c52223cd31;p=openssl

gcm128.c: P.-M. Hager has tipped about possibility to fold reductions
in gcm_ghash_4bit. Taking the idea a step further I've added extra
256+16 bytes of per-key storage, so that one can speak about 3rd variant
in addition to "256B" and "4KB": "528B" one. Commonly it should be
~50% faster than "256B" implementation or ~25% slower than "4KB" one.
---

diff --git a/crypto/modes/gcm128.c b/crypto/modes/gcm128.c
index 132c7892bc..8b1880cf5d 100644
--- a/crypto/modes/gcm128.c
+++ b/crypto/modes/gcm128.c
@@ -413,6 +413,7 @@ static void gcm_ghash_4bit(u64 Xi[2],const u128 Htable[16],
     size_t rem, nlo, nhi;
     const union { long one; char little; } is_endian = {1};
 
+#if 1
     do {
 	cnt  = 15;
 	nlo  = ((const u8 *)Xi)[15];
@@ -453,6 +454,117 @@ static void gcm_ghash_4bit(u64 Xi[2],const u128 Htable[16],
 		Z.hi ^= Htable[nlo].hi;
 		Z.lo ^= Htable[nlo].lo;
 	}
+#else
+    /*
+     * Extra 256+16 bytes per-key plus 512 bytes shared tables
+     * [should] give ~50% improvement... One could have PACK()-ed
+     * the rem_8bit even here, but priority is to minimize memory
+     * usage...
+     */ 
+    u128 Hshr4[16];	/* Htable shifted right by 4 bits */
+    u8   Hshl4[16];	/* Htable shifted left  by 4 bits */
+    static const unsigned short rem_8bit[256] = {
+	0x0000, 0x01C2, 0x0384, 0x0246, 0x0708, 0x06CA, 0x048C, 0x054E,
+	0x0E10, 0x0FD2, 0x0D94, 0x0C56, 0x0918, 0x08DA, 0x0A9C, 0x0B5E,
+	0x1C20, 0x1DE2, 0x1FA4, 0x1E66, 0x1B28, 0x1AEA, 0x18AC, 0x196E,
+	0x1230, 0x13F2, 0x11B4, 0x1076, 0x1538, 0x14FA, 0x16BC, 0x177E,
+	0x3840, 0x3982, 0x3BC4, 0x3A06, 0x3F48, 0x3E8A, 0x3CCC, 0x3D0E,
+	0x3650, 0x3792, 0x35D4, 0x3416, 0x3158, 0x309A, 0x32DC, 0x331E,
+	0x2460, 0x25A2, 0x27E4, 0x2626, 0x2368, 0x22AA, 0x20EC, 0x212E,
+	0x2A70, 0x2BB2, 0x29F4, 0x2836, 0x2D78, 0x2CBA, 0x2EFC, 0x2F3E,
+	0x7080, 0x7142, 0x7304, 0x72C6, 0x7788, 0x764A, 0x740C, 0x75CE,
+	0x7E90, 0x7F52, 0x7D14, 0x7CD6, 0x7998, 0x785A, 0x7A1C, 0x7BDE,
+	0x6CA0, 0x6D62, 0x6F24, 0x6EE6, 0x6BA8, 0x6A6A, 0x682C, 0x69EE,
+	0x62B0, 0x6372, 0x6134, 0x60F6, 0x65B8, 0x647A, 0x663C, 0x67FE,
+	0x48C0, 0x4902, 0x4B44, 0x4A86, 0x4FC8, 0x4E0A, 0x4C4C, 0x4D8E,
+	0x46D0, 0x4712, 0x4554, 0x4496, 0x41D8, 0x401A, 0x425C, 0x439E,
+	0x54E0, 0x5522, 0x5764, 0x56A6, 0x53E8, 0x522A, 0x506C, 0x51AE,
+	0x5AF0, 0x5B32, 0x5974, 0x58B6, 0x5DF8, 0x5C3A, 0x5E7C, 0x5FBE,
+	0xE100, 0xE0C2, 0xE284, 0xE346, 0xE608, 0xE7CA, 0xE58C, 0xE44E,
+	0xEF10, 0xEED2, 0xEC94, 0xED56, 0xE818, 0xE9DA, 0xEB9C, 0xEA5E,
+	0xFD20, 0xFCE2, 0xFEA4, 0xFF66, 0xFA28, 0xFBEA, 0xF9AC, 0xF86E,
+	0xF330, 0xF2F2, 0xF0B4, 0xF176, 0xF438, 0xF5FA, 0xF7BC, 0xF67E,
+	0xD940, 0xD882, 0xDAC4, 0xDB06, 0xDE48, 0xDF8A, 0xDDCC, 0xDC0E,
+	0xD750, 0xD692, 0xD4D4, 0xD516, 0xD058, 0xD19A, 0xD3DC, 0xD21E,
+	0xC560, 0xC4A2, 0xC6E4, 0xC726, 0xC268, 0xC3AA, 0xC1EC, 0xC02E,
+	0xCB70, 0xCAB2, 0xC8F4, 0xC936, 0xCC78, 0xCDBA, 0xCFFC, 0xCE3E,
+	0x9180, 0x9042, 0x9204, 0x93C6, 0x9688, 0x974A, 0x950C, 0x94CE,
+	0x9F90, 0x9E52, 0x9C14, 0x9DD6, 0x9898, 0x995A, 0x9B1C, 0x9ADE,
+	0x8DA0, 0x8C62, 0x8E24, 0x8FE6, 0x8AA8, 0x8B6A, 0x892C, 0x88EE,
+	0x83B0, 0x8272, 0x8034, 0x81F6, 0x84B8, 0x857A, 0x873C, 0x86FE,
+	0xA9C0, 0xA802, 0xAA44, 0xAB86, 0xAEC8, 0xAF0A, 0xAD4C, 0xAC8E,
+	0xA7D0, 0xA612, 0xA454, 0xA596, 0xA0D8, 0xA11A, 0xA35C, 0xA29E,
+	0xB5E0, 0xB422, 0xB664, 0xB7A6, 0xB2E8, 0xB32A, 0xB16C, 0xB0AE,
+	0xBBF0, 0xBA32, 0xB874, 0xB9B6, 0xBCF8, 0xBD3A, 0xBF7C, 0xBEBE };
+
+    /*
+     * This pre-processing phase slows down procedure by approximately
+     * same time as it makes each loop spin faster. In other words
+     * single block performance is approximately same as straightforward
+     * "4-bit" implementation, and then it goes only faster...
+     */
+    for (cnt=0; cnt<16; ++cnt) {
+	Z.hi = Htable[cnt].hi;
+	Z.lo = Htable[cnt].lo;
+	Hshr4[cnt].lo = (Z.hi<<60)|(Z.lo>>4);
+	Hshr4[cnt].hi = (Z.hi>>4);
+	Hshl4[cnt]    = (u8)(Z.lo<<4);
+    }
+
+    do {
+	nlo  = ((const u8 *)Xi)[15];
+	nlo ^= inp[15];
+	nhi  = nlo>>4;
+	nlo &= 0xf;
+
+	Z.hi = Htable[nlo].hi;
+	Z.lo = Htable[nlo].lo;
+
+	rem = (size_t)Z.lo&0xff;
+
+	Z.lo = (Z.hi<<56)|(Z.lo>>8);
+	Z.hi = (Z.hi>>8);
+
+	Z.hi ^= Hshr4[nhi].hi;
+	Z.lo ^= Hshr4[nhi].lo;
+	Z.hi ^= (u64)rem_8bit[rem^Hshl4[nhi]]<<48;
+
+	for (cnt=14; cnt>0; --cnt) {
+		nlo  = ((const u8 *)Xi)[cnt];
+		nlo ^= inp[cnt];
+		nhi  = nlo>>4;
+		nlo &= 0xf;
+
+		Z.hi ^= Htable[nlo].hi;
+		Z.lo ^= Htable[nlo].lo;
+
+		rem = (size_t)Z.lo&0xff;
+
+		Z.lo = (Z.hi<<56)|(Z.lo>>8);
+		Z.hi = (Z.hi>>8);
+
+		Z.hi ^= Hshr4[nhi].hi;
+		Z.lo ^= Hshr4[nhi].lo;
+		Z.hi ^= (u64)rem_8bit[rem^Hshl4[nhi]]<<48;
+	}
+
+	nlo  = ((const u8 *)Xi)[0];
+	nlo ^= inp[0];
+	nhi  = nlo>>4;
+	nlo &= 0xf;
+
+	Z.hi ^= Htable[nlo].hi;
+	Z.lo ^= Htable[nlo].lo;
+
+	rem = (size_t)Z.lo&0xf;
+
+	Z.lo = (Z.hi<<60)|(Z.lo>>4);
+	Z.hi = (Z.hi>>4);
+
+	Z.hi ^= Htable[nhi].hi;
+	Z.lo ^= Htable[nhi].lo;
+	Z.hi ^= ((u64)rem_8bit[rem<<4])<<48;
+#endif
 
 	if (is_endian.little) {
 #ifdef BSWAP8