From 10e0615f30f6997675985b655f1cfd6823aa8615 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Thu, 28 Feb 2013 11:45:44 +0100
Subject: [PATCH] Reduce number of additions for x86_64 ecc_192_modp.
---
ChangeLog | 3 ++
x86_64/ecc-192-modp.asm | 69 +++++++++++++++++++++--------------------
2 files changed, 39 insertions(+), 33 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 7d397d71..93643d33 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
2013-02-28 Niels Möller <nisse@lysator.liu.se>
+ * x86_64/ecc-192-modp.asm: Reorganized to reduce number of
+ additions. Use setc instruction.
+
* examples/Makefile.in: Let $(HOGWEED_TARGETS) depend on
../libhogweed.a.
diff --git a/x86_64/ecc-192-modp.asm b/x86_64/ecc-192-modp.asm
index 288340f9..5812070b 100644
--- a/x86_64/ecc-192-modp.asm
+++ b/x86_64/ecc-192-modp.asm
@@ -20,50 +20,53 @@ C MA 02111-1301, USA.
.file "ecc-192-modp.asm"
define(<RP>, <%rsi>)
-define(<T1>, <%rdi>) C Overlaps unused ecc input
-define(<T2>, <%rcx>)
-define(<T3>, <%rdx>)
-define(<T4>, <%r8>)
-define(<T5>, <%r9>)
-define(<T6>, <%r10>)
+define(<T0>, <%rdi>) C Overlaps unused ecc input
+define(<T1>, <%rcx>)
+define(<T2>, <%rdx>)
+define(<T3>, <%r8>)
+define(<H>, <%r9>)
+define(<C1>, <%r10>)
+define(<C2>, <%r11>)
C ecc_192_modp (const struct ecc_curve *ecc, mp_limb_t *rp)
.text
ALIGN(4)
PROLOGUE(nettle_ecc_192_modp)
W64_ENTRY(2, 0)
- C First: (B+1)*{r5, r4} < B^3 + B^2 - B
- mov 32(RP), T1
- mov 40(RP), T2
- mov T2, T3
- xor T4, T4
- add T1, T2
- adc $0, T3
- adc $0, T4
+ mov 16(RP), T2
+ mov 24(RP), T3
+ mov 40(RP), H
+ xor C1, C1
+ xor C2, C2
- add 8(RP), T1
- adc 16(RP), T2
- adc 24(RP), T3
- adc $0, T4
- C Sum is < 2B^4 + B^3 - B - 1, so {T4, T3} < 3B
+ add H, T2
+ adc H, T3
+ C Carry to be added in at T1 and T2
+ setc LREG(C2)
+
+ mov 8(RP), T1
+ mov 32(RP), H
+ adc H, T1
+ adc H, T2
+ C Carry to be added in at T0 and T1
+ setc LREG(C1)
+
+ mov (RP), T0
+ adc T3, T0
+ adc T3, T1
+ adc $0, C2
- C Next: (B+1) * {T4, T3} < 3B^2 + 2B
- mov T4, T5
- add T3, T4
- adc $0, T5
+ C Add in C1 and C2
+ add C1, T1
+ adc C2, T2
+ setc LREG(C1)
- xor T6, T6
- add (RP), T3
- adc T4, T1
- adc T5, T2
- adc $0, T6
-
- C Fold in final carry.
- add T6, T3
- adc T6, T1
+ C Fold final carry.
+ adc $0, T0
+ adc C1, T1
adc $0, T2
- mov T3, (RP)
+ mov T0, (RP)
mov T1, 8(RP)
mov T2, 16(RP)
--
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