From e0cde326bd1d7d30caddb011567af1a7e95e7cd0 Mon Sep 17 00:00:00 2001
From: Sun Yimin <emmansun@users.noreply.github.com>
Date: Thu, 23 Dec 2021 16:37:52 +0800
Subject: [PATCH] Updated MFMM (markdown)

---
 MFMM.md | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/MFMM.md b/MFMM.md
index 3b5081a..cf307d2 100644
--- a/MFMM.md
+++ b/MFMM.md
@@ -148,9 +148,41 @@ acc0, acc1, acc2, acc3, acc4, acc5是64位寄存器
 
     (carry6, acc4) = acc4 + t1
     acc5 = carry6
-
     ======
 
+考虑以下算法(主要就是一轮加法，一轮减法)：
+
+       acc4,         acc3,         acc2,        acc1
+     + acc0,         0,            0,           (acc0 - L(acc0*2^32))
+     - H(acc0*2^32)  L(acc0*2^32)  H(acc0*2^32)
+
+    =》继续优化
+       acc4,                          acc3,         acc2,        acc1
+     + (acc0 - H(acc0*2^32)),         0,            0,           (acc0 - L(acc0*2^32))
+     -                                L(acc0*2^32)  H(acc0*2^32)
+
+acc0 - H(acc0 * 2^32) >= 0, acc0 - L(acc0 * 2^32) >= 0 显然。
+
+ 	MOVQ acc0, AX
+	MOVQ acc0, DX
+	SHLQ $32, AX
+	SHRQ $32, DX
+	MOVQ acc0, t0
+	SUBQ AX, t0
+	MOVQ acc0, t1
+	SUBQ DX, t1
+	
+	ADDQ t0, acc1
+	ADCQ $0, acc2
+	ADCQ $0, acc3
+	ADCQ t1, acc4
+	ADCQ $0, acc5
+	
+	SUBQ DX, acc2
+	SBBQ AX, acc3
+	SBBQ $0, acc4
+	SBBQ $0, acc5
+
 ### 第三步，计算 X * Y1，并且和tmp相加
     tmp = tmp + X * Y1，按逐个64位字相加的原则：