[cfe-dev] clang does not use sincos with -O2 but gcc does

[Dennis Luehring via cfe-dev]

https://godbolt.org/g/Y0sjoj

why do clang needs the -ffast-math option to use the sincos function here?
gcc uses the sincos function without -ffast-math

clang -O2 -march=native (call sin, call cos)
clang -O3 -march=native (call sin, call cos)
clang -O2 -march=native -ffast-math (call sincos)

gcc -O2 (call sincos)