C is a constant which can be sign-extended from 8 bits without value loss,
and op is one of: add, sub, imul, and, or, xor.

This allows the JIT to emit the one byte version of the constant instead of
the two or 4 byte version.  Because these instructions are very common, this
can save a LOT of code space.  For example, I sampled two benchmarks, 176.gcc
and 254.gap.

BM        Old     New    Reduction
176.gcc 2673621 2548962  4.89%
254.gap  498261  475104  4.87%

Note that while the percentage is not spectacular, this did eliminate
124.6 _KILOBYTES_ of codespace from gcc.  Not bad.

Note that this doesn't effect the llc version at all, because the assembler
already does this optimization.

llvm-svn: 9284

* Implement R1 = R2 * C where R1 and R2 are 32 or 16 bits. This avoids an
  extra copy into a register, reducing register pressure.

llvm-svn: 9278

llvm-svn: 9266

llvm-svn: 7872

llvm-svn: 7755

llvm-svn: 7730

llvm-svn: 7725

llvm-svn: 7635

Physical registers should not float around.

llvm-svn: 7587

testing, the subtracts are because I was in the neighborhood.

llvm-svn: 7581

llvm-svn: 7580

llvm-svn: 7564

llvm-svn: 7537