Botan 2.19.2
Crypto and TLS for C&
mul128.h
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1/*
2* 64x64->128 bit multiply operation
3* (C) 2013,2015 Jack Lloyd
4*
5* Botan is released under the Simplified BSD License (see license.txt)
6*/
7
8#ifndef BOTAN_UTIL_MUL128_H_
9#define BOTAN_UTIL_MUL128_H_
10
11#include <botan/types.h>
12
14
15namespace Botan {
16
17#if defined(__SIZEOF_INT128__) && defined(BOTAN_TARGET_CPU_HAS_NATIVE_64BIT)
18 #define BOTAN_TARGET_HAS_NATIVE_UINT128
19
20 // Prefer TI mode over __int128 as GCC rejects the latter in pendantic mode
21 #if defined(__GNUG__)
22 typedef unsigned int uint128_t __attribute__((mode(TI)));
23 #else
24 typedef unsigned __int128 uint128_t;
25 #endif
26#endif
27
28}
29
30#if defined(BOTAN_TARGET_HAS_NATIVE_UINT128)
31
32#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) \
33 do { \
34 const uint128_t r = static_cast<uint128_t>(a) * b; \
35 *hi = (r >> 64) & 0xFFFFFFFFFFFFFFFF; \
36 *lo = (r ) & 0xFFFFFFFFFFFFFFFF; \
37 } while(0)
38
39#elif defined(BOTAN_BUILD_COMPILER_IS_MSVC) && defined(BOTAN_TARGET_CPU_HAS_NATIVE_64BIT)
40
41#include <intrin.h>
42#pragma intrinsic(_umul128)
43
44#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) \
45 do { *lo = _umul128(a, b, hi); } while(0)
46
47#elif defined(BOTAN_USE_GCC_INLINE_ASM)
48
49#if defined(BOTAN_TARGET_ARCH_IS_X86_64)
50
51#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) do { \
52 asm("mulq %3" : "=d" (*hi), "=a" (*lo) : "a" (a), "rm" (b) : "cc"); \
53 } while(0)
54
55#elif defined(BOTAN_TARGET_ARCH_IS_ALPHA)
56
57#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) do { \
58 asm("umulh %1,%2,%0" : "=r" (*hi) : "r" (a), "r" (b)); \
59 *lo = a * b; \
60} while(0)
61
62#elif defined(BOTAN_TARGET_ARCH_IS_IA64)
63
64#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) do { \
65 asm("xmpy.hu %0=%1,%2" : "=f" (*hi) : "f" (a), "f" (b)); \
66 *lo = a * b; \
67} while(0)
68
69#elif defined(BOTAN_TARGET_ARCH_IS_PPC64)
70
71#define BOTAN_FAST_64X64_MUL(a,b,lo,hi) do { \
72 asm("mulhdu %0,%1,%2" : "=r" (*hi) : "r" (a), "r" (b) : "cc"); \
73 *lo = a * b; \
74} while(0)
75
76#endif
77
78#endif
79
80namespace Botan {
81
82/**
83* Perform a 64x64->128 bit multiplication
84*/
85inline void mul64x64_128(uint64_t a, uint64_t b, uint64_t* lo, uint64_t* hi)
86 {
87#if defined(BOTAN_FAST_64X64_MUL)
88 BOTAN_FAST_64X64_MUL(a, b, lo, hi);
89#else
90
91 /*
92 * Do a 64x64->128 multiply using four 32x32->64 multiplies plus
93 * some adds and shifts. Last resort for CPUs like UltraSPARC (with
94 * 64-bit registers/ALU, but no 64x64->128 multiply) or 32-bit CPUs.
95 */
96 const size_t HWORD_BITS = 32;
97 const uint32_t HWORD_MASK = 0xFFFFFFFF;
98
99 const uint32_t a_hi = (a >> HWORD_BITS);
100 const uint32_t a_lo = (a & HWORD_MASK);
101 const uint32_t b_hi = (b >> HWORD_BITS);
102 const uint32_t b_lo = (b & HWORD_MASK);
103
104 uint64_t x0 = static_cast<uint64_t>(a_hi) * b_hi;
105 uint64_t x1 = static_cast<uint64_t>(a_lo) * b_hi;
106 uint64_t x2 = static_cast<uint64_t>(a_hi) * b_lo;
107 uint64_t x3 = static_cast<uint64_t>(a_lo) * b_lo;
108
109 // this cannot overflow as (2^32-1)^2 + 2^32-1 < 2^64-1
110 x2 += x3 >> HWORD_BITS;
111
112 // this one can overflow
113 x2 += x1;
114
115 // propagate the carry if any
116 x0 += static_cast<uint64_t>(static_cast<bool>(x2 < x1)) << HWORD_BITS;
117
118 *hi = x0 + (x2 >> HWORD_BITS);
119 *lo = ((x2 & HWORD_MASK) << HWORD_BITS) + (x3 & HWORD_MASK);
120#endif
121 }
122
123}
124
125#endif
#define BOTAN_FUTURE_INTERNAL_HEADER(hdr)
Definition: compiler.h:136
Definition: alg_id.cpp:13
void mul64x64_128(uint64_t a, uint64_t b, uint64_t *lo, uint64_t *hi)
Definition: mul128.h:85