Merge branch 'approx_hpvm' of https://gitlab.engr.illinois.edu/llvm/hpvm into approx_hpvm

.../projects/hpvm-tensor-rt/opentuner/data/alexnet/knobs.txt

...projects/hpvm-tensor-rt/opentuner/data/alexnet2/knobs.txt

llvm/projects/hpvm-tensor-rt/opentuner/data/global_knobs.txt

llvm/projects/hpvm-tensor-rt/opentuner/data/lenet/knobs.txt

...rojects/hpvm-tensor-rt/opentuner/data/mobilenet/knobs.txt

...hpvm-tensor-rt/opentuner/data/mobilenet_shallow/knobs.txt

llvm/projects/hpvm-tensor-rt/opentuner/data/resnet/knobs.txt

...cts/hpvm-tensor-rt/opentuner/data/vgg16_cifar10/knobs.txt

...ts/hpvm-tensor-rt/opentuner/data/vgg16_cifar100/knobs.txt

...hpvm-tensor-rt/tensor_runtime/include/approx_simulation.h

...hpvm-tensor-rt/tensor_runtime/include/approx_techniques.h

...pvm-tensor-rt/tensor_runtime/include/approx_techniques2.h