feat: fused mul_hilo for 64-bit batches (shared 32x32->64 partials) #4986

	name: C++ compatibility build
	on: [push, pull_request]
	concurrency:
	group: ${{ github.workflow }}-${{ github.job }}-${{ github.ref }}
	cancel-in-progress: true

	jobs:
	build-unix:
	name: 'Unix C++${{ matrix.cxx-version }}'
	runs-on: ubuntu-latest
	strategy:
	matrix:
	cxx-version: [14, 17, 20]
	steps:
	- uses: actions/checkout@v6
	- name: Setup
	run: cmake -B build/ -DBUILD_TESTS=ON -DDOWNLOAD_DOCTEST=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_STANDARD=${{matrix.cxx-version}}
	- name: Build
	run: cmake --build build/
	- name: Test
	run: ./build/test/test_xsimd

	build-msvc:
	name: 'MSVC C++${{ matrix.cxx-version }}'
	defaults:
	run:
	shell: bash {0}
	runs-on: windows-2022
	strategy:
	matrix:
	cxx-version: [14, 17, 20]
	steps:
	- name: Setup compiler
	uses: ilammy/msvc-dev-cmd@v1
	with:
	arch: amd64
	- name: Setup Ninja
	run: \|
	python3 -m pip install --upgrade pip setuptools wheel
	python3 -m pip install ninja
	- uses: actions/checkout@v6
	- name: Setup
	run: cmake -B build/ -DBUILD_TESTS=ON -DDOWNLOAD_DOCTEST=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_STANDARD=${{matrix.cxx-version}} -G Ninja
	- name: Build
	run: cmake --build build/
	- name: Test
	run: ./build/test/test_xsimd

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