[X86] Convert esp-relative movs of function arguments into pushes, step 1
This handles the simplest case for mov -> push conversion:
1. x86-32 calling convention, everything is passed through the stack.
2. There is no reserved call frame.
3. Only registers or immediates are pushed, no attempt to combine a mem-reg-mem sequence into a single PUSHmm.
Differential Revision: http://reviews.llvm.org/D6503
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223757
91177308-0d34-0410-b5e6-
96231b3b80d8