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authorGravatar Abseil Team <absl-team@google.com>2018-01-18 12:42:26 -0800
committerGravatar vslashg <gfalcon@google.com>2018-01-18 16:14:22 -0500
commit52a2458965fc2ef6f03fb692b253a1ca56ff6e39 (patch)
tree9a954f4a03f9ac08db891baf5f39b29f5c0d7d23 /absl/numeric/int128.h
parent5a8de8a37e3e282d22f69ca67b4aba8e4cca63ae (diff)
Changes imported from Abseil "staging" branch:
- 3f758237a43af1f277990492701d26d1153b4d74 Generalize the construction/destruction tests, to prepare... by Greg Falcon <gfalcon@google.com> - 7bea88f74fbac34b0c0b00b8b832a544988b9465 Simplify non intrinsic uint128 multiply. by Alex Strelnikov <strel@google.com> GitOrigin-RevId: 3f758237a43af1f277990492701d26d1153b4d74 Change-Id: Idd9a2df0b90403f10f56bb66d30b76a8ba9f50e7
Diffstat (limited to 'absl/numeric/int128.h')
-rw-r--r--absl/numeric/int128.h15
1 files changed, 2 insertions, 13 deletions
diff --git a/absl/numeric/int128.h b/absl/numeric/int128.h
index 94d2f7ce..5e1b3f03 100644
--- a/absl/numeric/int128.h
+++ b/absl/numeric/int128.h
@@ -570,25 +570,14 @@ inline uint128& uint128::operator*=(uint128 other) {
static_cast<unsigned __int128>(other);
return *this;
#else // ABSL_HAVE_INTRINSIC128
- uint64_t a96 = hi_ >> 32;
- uint64_t a64 = hi_ & 0xffffffff;
uint64_t a32 = lo_ >> 32;
uint64_t a00 = lo_ & 0xffffffff;
- uint64_t b96 = other.hi_ >> 32;
- uint64_t b64 = other.hi_ & 0xffffffff;
uint64_t b32 = other.lo_ >> 32;
uint64_t b00 = other.lo_ & 0xffffffff;
- // multiply [a96 .. a00] x [b96 .. b00]
- // terms higher than c96 disappear off the high side
- // terms c96 and c64 are safe to ignore carry bit
- uint64_t c96 = a96 * b00 + a64 * b32 + a32 * b64 + a00 * b96;
- uint64_t c64 = a64 * b00 + a32 * b32 + a00 * b64;
- this->hi_ = (c96 << 32) + c64;
- this->lo_ = 0;
- // add terms after this one at a time to capture carry
+ hi_ = hi_ * other.lo_ + lo_ * other.hi_ + a32 * b32;
+ lo_ = a00 * b00;
*this += uint128(a32 * b00) << 32;
*this += uint128(a00 * b32) << 32;
- *this += a00 * b00;
return *this;
#endif // ABSL_HAVE_INTRINSIC128
}