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[APInt] Allow GreatestCommonDivisor to take rvalue inputs efficiently. Use moves instead of copies in the loop.

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Summary:
GreatestComonDivisor currently makes a copy of both its inputs. Then in the loop we do one move and two copies, plus any allocation the urem call does.

This patch changes it to take its inputs by value so that we can do a move of any rvalue inputs instead of copying. Then in the loop we do 3 move assignments and no copies. This way the only possible allocations we have in the loop is from the urem call.

Reviewers: dblaikie, RKSimon, hans

Reviewed By: dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31572

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299314 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Craig Topper 2017-04-01 20:30:57 +00:00
parent 084c1ea3b4
commit 2ea3d99e26
2 changed files with 6 additions and 8 deletions
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4
include/llvm/ADT/APInt.h
View File

@ -1937,8 +1937,8 @@ inline bool isShiftedMask(const APInt &APIVal) {
/// This function returns the greatest common divisor of the two APInt values
/// using Euclid's algorithm.
///
/// \returns the greatest common divisor of Val1 and Val2
APInt GreatestCommonDivisor(const APInt &Val1, const APInt &Val2);
/// \returns the greatest common divisor of \param A and \param B.
APInt GreatestCommonDivisor(APInt A, APInt B);
/// \brief Converts the given APInt to a double value.
///

10
lib/Support/APInt.cpp
View File

@ -876,13 +876,11 @@ APInt APInt::reverseBits() const {
return Reversed;
}
APInt llvm::APIntOps::GreatestCommonDivisor(const APInt& API1,
const APInt& API2) {
APInt A = API1, B = API2;
APInt llvm::APIntOps::GreatestCommonDivisor(APInt A, APInt B) {
while (!!B) {
APInt T = B;
B = A.urem(B);
A = T;
APInt R = A.urem(B);
A = std::move(B);
B = std::move(R);
}
return A;
}