search for: vzeroupperinserter

We have been using LLVM 3.1 to support JITing of AVX. From dumping the MC generating by the MCJIT I noticed it always emits 'VZEROUPPER' to clear the high 128 bit before calling another function. In some cases I know the function called either only use AVX or does not use SSE. I will like to inform the backend it is safe not to emit that instruction. Have not been able to figure out how