From 2ea3d99e26057f64006769a0777d59c4e26f28f5 Mon Sep 17 00:00:00 2001 From: Craig Topper Date: Sat, 1 Apr 2017 20:30:57 +0000 Subject: [PATCH] [APInt] Allow GreatestCommonDivisor to take rvalue inputs efficiently. Use moves instead of copies in the loop. 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 --- include/llvm/ADT/APInt.h | 4 ++-- lib/Support/APInt.cpp | 10 ++++------ 2 files changed, 6 insertions(+), 8 deletions(-) diff --git a/include/llvm/ADT/APInt.h b/include/llvm/ADT/APInt.h index 402422507a5..56d5777288e 100644 --- a/include/llvm/ADT/APInt.h +++ b/include/llvm/ADT/APInt.h @@ -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. /// diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp index d6139504f9a..0d4255da7f0 100644 --- a/lib/Support/APInt.cpp +++ b/lib/Support/APInt.cpp @@ -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; } -- 2.40.0