[PATCH] [X86] Convert esp-relative movs of function arguments to pushes, step 1

[Michael Kuperstein]

Thanks for the review, Nadav!

1) Yes, the mov -> push transformation should be beneficial (or, at least, not harmful) on all recent Intel architectures when the pushed value is an immediate or a register (not memory), which is what this patch handles.
2) I don't really expect a performance change, in either direction - this step is mostly for code size. 
You're absolutely right, though, I should verify that with the test-suite. If there are any anomalous results, I'll post them here.
3) I used std::map because it guarantees ordered iteration, which is useful here. I thought DenseMap doesn't have that guarantee. Am I wrong?

Michael

http://reviews.llvm.org/D6503