Relax exp and pow accuracy requirement
Relax exp and pow accuracy requirement

llvm trunk pre avx now simplifies these more aggressively.

tdenniston/Halide,smxlong/Halide,tdenniston/Halide,kenkuang1213/Halide,smxlong/Halide,kgnk/Halide,dan-tull/Halide,ronen/Halide,dougkwan/Halide,dougkwan/Halide,delcypher/Halide,delcypher/Halide,ronen/Halide,kenkuang1213/Halide,dan-tull/Halide,mcanthony/Halide,delcypher/Halide,kgnk/Halide,jiawen/Halide,ronen/Halide,kgnk/Halide,adasworks/Halide,mcanthony/Halide,kenkuang1213/Halide,smxlong/Halide,psuriana/Halide,dan-tull/Halide,ronen/Halide,ronen/Halide,kenkuang1213/Halide,psuriana/Halide,delcypher/Halide,tdenniston/Halide,delcypher/Halide,dan-tull/Halide,tdenniston/Halide,dan-tull/Halide,dougkwan/Halide,mcanthony/Halide,mcanthony/Halide,myrtleTree33/Halide,psuriana/Halide,smxlong/Halide,jiawen/Halide,dan-tull/Halide,myrtleTree33/Halide,dougkwan/Halide,jiawen/Halide,adasworks/Halide,dougkwan/Halide,kgnk/Halide,adasworks/Halide,tdenniston/Halide,tdenniston/Halide,smxlong/Halide,dan-tull/Halide,jiawen/Halide,myrtleTree33/Halide,dan-tull/Halide,kenkuang1213/Halide,psuriana/Halide,ronen/Halide,psuriana/Halide,dougkwan/Halide,adasworks/Halide,jiawen/Halide,delcypher/Halide,mcanthony/Halide,adasworks/Halide,myrtleTree33/Halide,dougkwan/Halide,smxlong/Halide,kenkuang1213/Halide,tdenniston/Halide,delcypher/Halide,kgnk/Halide,jiawen/Halide,psuriana/Halide,tdenniston/Halide,adasworks/Halide,myrtleTree33/Halide,jiawen/Halide,adasworks/Halide,kgnk/Halide,delcypher/Halide,psuriana/Halide,kenkuang1213/Halide,kgnk/Halide,dougkwan/Halide,ronen/Halide,mcanthony/Halide,kenkuang1213/Halide,mcanthony/Halide,smxlong/Halide,mcanthony/Halide,adasworks/Halide,smxlong/Halide,kgnk/Halide,myrtleTree33/Halide,myrtleTree33/Halide,myrtleTree33/Halide,ronen/Halide