If pseudoToMCOpcode failed, we would return the original opcode, so operands
would be swapped, but the instruction would remain the same.
It resulted in LSHLREV a, b ---> LSHLREV b, a.
This fixes Glamor text rendering and
piglit/arb_sample_shading-builtin-gl-sample-mask on VI.
This is a candidate for stable branches.
v2: the test was simplified by Tom Stellard
llvm-svn: 240824
Marek Olsak