Emit ASM input in a constant context
Some ASM input constraints (e.g., "i" and "n") require immediate values. At O0,
very few code transformations are performed. So if we cannot resolve to an
immediate when emitting the ASM input we shouldn't delay its processing.
Reviewers: rsmith, efriedma
Reviewed By: efriedma
Subscribers: rehana, efriedma, craig.topper, jyknight, cfe-commits
Differential Revision: https://reviews.llvm.org/D55616