[PATCH 4/4] mpi/generic: use longlong.h for carry handling

[Jussi Kivilinna]

* mpi/generic/mpih-add1.c (_gcry_mpih_add_n): Use add_ssaaaa for
carry handling.
* mpi/generic/mpih-mul1.c (_gcry_mpih_mul_1): Likewise.
* mpi/generic/mpih-mul2.c (_gcry_mpih_addmul_1): Likewise.
* mpi/generic/mpih-mul3.c (_gcry_mpih_submul_1): Use add_ssaaaa
and sub_ddmmss for carry handling.
* mpi/generic/mpih-sub1.c (_gcry_mpih_sub_n): Likewise.
--

Signed-off-by: Jussi Kivilinna <jussi.kivilinna at iki.fi>
---
 mpi/generic/mpih-add1.c | 15 ++++++++-------
 mpi/generic/mpih-mul1.c |  7 +++----
 mpi/generic/mpih-mul2.c | 13 +++++--------
 mpi/generic/mpih-mul3.c | 14 ++++++--------
 mpi/generic/mpih-sub1.c | 16 +++++++++-------
 5 files changed, 31 insertions(+), 34 deletions(-)

diff --git a/mpi/generic/mpih-add1.c b/mpi/generic/mpih-add1.c
index 0a51f06c..4c95609b 100644
--- a/mpi/generic/mpih-add1.c
+++ b/mpi/generic/mpih-add1.c
@@ -1,5 +1,5 @@
 /* mpihelp-add_1.c  -  MPI helper functions
- * Copyright (C) 1994, 1996, 1997, 1998, 
+ * Copyright (C) 1994, 1996, 1997, 1998,
  *               2000, 2002 Free Software Foundation, Inc.
  *
  * This file is part of Libgcrypt.
@@ -48,16 +48,17 @@ _gcry_mpih_add_n (mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
   res_ptr -= j;
 
   cy = 0;
-  do 
+  do
     {
       y = s2_ptr[j];
       x = s1_ptr[j];
-      y += cy;		  /* add previous carry to one addend */
-      cy = y < cy;	  /* get out carry from that addition */
-      y += x; 		  /* add other addend */
-      cy += y < x;	  /* get out carry from that add, combine */
+      /* Add previous carry to one addend and get out carry from
+       * that addition.  */
+      add_ssaaaa (cy, y, 0, y, 0, cy);
+      /* Add other addend and get out carry from that add, combine.  */
+      add_ssaaaa (cy, y, cy, y, 0, x);
       res_ptr[j] = y;
-    } 
+    }
   while ( ++j );
 
   return cy;
diff --git a/mpi/generic/mpih-mul1.c b/mpi/generic/mpih-mul1.c
index e88be914..accae1dc 100644
--- a/mpi/generic/mpih-mul1.c
+++ b/mpi/generic/mpih-mul1.c
@@ -48,13 +48,12 @@ _gcry_mpih_mul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
   res_ptr -= j;
 
   cy_limb = 0;
-  do 
+  do
     {
       umul_ppmm( prod_high, prod_low, s1_ptr[j], s2_limb );
-      prod_low += cy_limb;
-      cy_limb = (prod_low < cy_limb?1:0) + prod_high;
+      add_ssaaaa( cy_limb, prod_low, prod_high, prod_low, 0, cy_limb );
       res_ptr[j] = prod_low;
-    } 
+    }
   while( ++j );
 
   return cy_limb;
diff --git a/mpi/generic/mpih-mul2.c b/mpi/generic/mpih-mul2.c
index bc925e01..931438dd 100644
--- a/mpi/generic/mpih-mul2.c
+++ b/mpi/generic/mpih-mul2.c
@@ -48,20 +48,17 @@ _gcry_mpih_addmul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
   s1_ptr -= j;
 
   cy_limb = 0;
-  do 
+  do
     {
       umul_ppmm( prod_high, prod_low, s1_ptr[j], s2_limb );
-
-      prod_low += cy_limb;
-      cy_limb = (prod_low < cy_limb?1:0) + prod_high;
+      add_ssaaaa( cy_limb, prod_low, prod_high, prod_low, 0, cy_limb );
 
       x = res_ptr[j];
-      prod_low = x + prod_low;
-      cy_limb += prod_low < x?1:0;
+      add_ssaaaa( cy_limb, prod_low, cy_limb, prod_low, 0, x );
       res_ptr[j] = prod_low;
-    } 
+    }
   while ( ++j );
-    
+
   return cy_limb;
 }
 
diff --git a/mpi/generic/mpih-mul3.c b/mpi/generic/mpih-mul3.c
index 4ecd2c6b..7372c845 100644
--- a/mpi/generic/mpih-mul3.c
+++ b/mpi/generic/mpih-mul3.c
@@ -36,7 +36,7 @@ mpi_limb_t
 _gcry_mpih_submul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
 		  mpi_size_t s1_size, mpi_limb_t s2_limb)
 {
-  mpi_limb_t cy_limb;
+  mpi_limb_t cy_limb, borrow;
   mpi_size_t j;
   mpi_limb_t prod_high, prod_low;
   mpi_limb_t x;
@@ -48,18 +48,16 @@ _gcry_mpih_submul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
   s1_ptr -= j;
 
   cy_limb = 0;
-  do 
+  do
     {
       umul_ppmm( prod_high, prod_low, s1_ptr[j], s2_limb);
-
-      prod_low += cy_limb;
-      cy_limb = (prod_low < cy_limb?1:0) + prod_high;
+      add_ssaaaa( cy_limb, prod_low, prod_high, prod_low, 0, cy_limb );
 
       x = res_ptr[j];
-      prod_low = x - prod_low;
-      cy_limb += prod_low > x?1:0;
+      sub_ddmmss( borrow, prod_low, 0, x, 0, prod_low );
+      cy_limb -= borrow;
       res_ptr[j] = prod_low;
-    } 
+    }
   while( ++j );
 
   return cy_limb;
diff --git a/mpi/generic/mpih-sub1.c b/mpi/generic/mpih-sub1.c
index b8eff0db..bb51487c 100644
--- a/mpi/generic/mpih-sub1.c
+++ b/mpi/generic/mpih-sub1.c
@@ -35,7 +35,7 @@ mpi_limb_t
 _gcry_mpih_sub_n( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
 				  mpi_ptr_t s2_ptr, mpi_size_t size)
 {
-  mpi_limb_t x, y, cy;
+  mpi_limb_t x, y, cy, borrow;
   mpi_size_t j;
 
   /* The loop counter and index J goes from -SIZE to -1.  This way
@@ -48,16 +48,18 @@ _gcry_mpih_sub_n( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
   res_ptr -= j;
 
   cy = 0;
-  do 
+  do
     {
       y = s2_ptr[j];
       x = s1_ptr[j];
-      y += cy;		  /* add previous carry to subtrahend */
-      cy = y < cy;		  /* get out carry from that addition */
-      y = x - y;		  /* main subtract */
-      cy += y > x;		  /* get out carry from the subtract, combine */
+      /* Add previous carry to subtrahend and get out carry from
+       * that addition.  */
+      add_ssaaaa (cy, y, 0, y, 0, cy);
+      /* Main subtract and get out carry from the subtract, combine.  */
+      sub_ddmmss( borrow, y, 0, x, 0, y );
+      cy -= borrow;
       res_ptr[j] = y;
-    } 
+    }
   while( ++j );
 
   return cy;
-- 
2.43.0