LoongArch: vDSO: Tune chacha implementation

As Christophe pointed out, tuning the chacha implementation by
scheduling the instructions like what GCC does can improve the
performance.

The tuning does not introduce too much complexity (basically it's just
reordering some instructions). And the tuning does not hurt readibility
too much: actually the tuned code looks even more similar to a
textbook-style implementation based on 128-bit vectors.  So overall it's
a good deal to me.

Tested with vdso_test_getchacha and benched with vdso_test_getrandom.
On a LA664 the speedup is 5%, and I expect a larger speedup on LA[2-4]64
with a lower issue rate.

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/all/77655d9e-fc05-4300-8f0d-7b2ad840d091@csgroup.eu/
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/arch/loongarch/vdso/vgetrandom-chacha.S b/arch/loongarch/vdso/vgetrandom-chacha.S
index 7e86a50f6e85c369d9390c55d661b680b1532604..c2733e6c3a8de87d63b334397d3104f34fefd288 100644 (file)
--- a/arch/loongarch/vdso/vgetrandom-chacha.S
+++ b/arch/loongarch/vdso/vgetrandom-chacha.S
@@ -9,23 +9,11 @@
 
 .text
 
-/* Salsa20 quarter-round */
-.macro QR      a b c d
-       add.w           \a, \a, \b
-       xor             \d, \d, \a
-       rotri.w         \d, \d, 16
-
-       add.w           \c, \c, \d
-       xor             \b, \b, \c
-       rotri.w         \b, \b, 20
-
-       add.w           \a, \a, \b
-       xor             \d, \d, \a
-       rotri.w         \d, \d, 24
-
-       add.w           \c, \c, \d
-       xor             \b, \b, \c
-       rotri.w         \b, \b, 25
+.macro OP_4REG op d0 d1 d2 d3 s0 s1 s2 s3
+       \op     \d0, \d0, \s0
+       \op     \d1, \d1, \s1
+       \op     \d2, \d2, \s2
+       \op     \d3, \d3, \s3
 .endm
 
 /*
@@ -74,6 +62,23 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
 /* Reuse i as copy3 */
 #define copy3          i
 
+/* Packs to be used with OP_4REG */
+#define line0          state0, state1, state2, state3
+#define line1          state4, state5, state6, state7
+#define line2          state8, state9, state10, state11
+#define line3          state12, state13, state14, state15
+
+#define line1_perm     state5, state6, state7, state4
+#define line2_perm     state10, state11, state8, state9
+#define line3_perm     state15, state12, state13, state14
+
+#define copy           copy0, copy1, copy2, copy3
+
+#define _16            16, 16, 16, 16
+#define _20            20, 20, 20, 20
+#define _24            24, 24, 24, 24
+#define _25            25, 25, 25, 25
+
        /*
         * The ABI requires s0-s9 saved, and sp aligned to 16-byte.
         * This does not violate the stack-less requirement: no sensitive data
@@ -126,16 +131,38 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
        li.w            i, 10
 .Lpermute:
        /* odd round */
-       QR              state0, state4, state8, state12
-       QR              state1, state5, state9, state13
-       QR              state2, state6, state10, state14
-       QR              state3, state7, state11, state15
+       OP_4REG add.w   line0, line1
+       OP_4REG xor     line3, line0
+       OP_4REG rotri.w line3, _16
+
+       OP_4REG add.w   line2, line3
+       OP_4REG xor     line1, line2
+       OP_4REG rotri.w line1, _20
+
+       OP_4REG add.w   line0, line1
+       OP_4REG xor     line3, line0
+       OP_4REG rotri.w line3, _24
+
+       OP_4REG add.w   line2, line3
+       OP_4REG xor     line1, line2
+       OP_4REG rotri.w line1, _25
 
        /* even round */
-       QR              state0, state5, state10, state15
-       QR              state1, state6, state11, state12
-       QR              state2, state7, state8, state13
-       QR              state3, state4, state9, state14
+       OP_4REG add.w   line0, line1_perm
+       OP_4REG xor     line3_perm, line0
+       OP_4REG rotri.w line3_perm, _16
+
+       OP_4REG add.w   line2_perm, line3_perm
+       OP_4REG xor     line1_perm, line2_perm
+       OP_4REG rotri.w line1_perm, _20
+
+       OP_4REG add.w   line0, line1_perm
+       OP_4REG xor     line3_perm, line0
+       OP_4REG rotri.w line3_perm, _24
+
+       OP_4REG add.w   line2_perm, line3_perm
+       OP_4REG xor     line1_perm, line2_perm
+       OP_4REG rotri.w line1_perm, _25
 
        addi.w          i, i, -1
        bnez            i, .Lpermute
@@ -147,10 +174,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
        li.w            copy3, 0x6b206574
 
        /* output[0,1,2,3] = copy[0,1,2,3] + state[0,1,2,3] */
-       add.w           state0, state0, copy0
-       add.w           state1, state1, copy1
-       add.w           state2, state2, copy2
-       add.w           state3, state3, copy3
+       OP_4REG add.w   line0, copy
        st.w            state0, output, 0
        st.w            state1, output, 4
        st.w            state2, output, 8
@@ -165,10 +189,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
        ld.w            state3, key, 12
 
        /* output[4,5,6,7] = state[0,1,2,3] + state[4,5,6,7] */
-       add.w           state4, state4, state0
-       add.w           state5, state5, state1
-       add.w           state6, state6, state2
-       add.w           state7, state7, state3
+       OP_4REG add.w   line1, line0
        st.w            state4, output, 16
        st.w            state5, output, 20
        st.w            state6, output, 24
@@ -181,10 +202,7 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
        ld.w            state3, key, 28
 
        /* output[8,9,10,11] = state[0,1,2,3] + state[8,9,10,11] */
-       add.w           state8, state8, state0
-       add.w           state9, state9, state1
-       add.w           state10, state10, state2
-       add.w           state11, state11, state3
+       OP_4REG add.w   line2, line0
        st.w            state8, output, 32
        st.w            state9, output, 36
        st.w            state10, output, 40