[Mesa-dev] [PATCH 0/2] Eliminate unused built-in variables

[Ian Romanick]

This series goes on top of my previous series, but I wish I had done it
first.  I was getting ready to move on to ir_rvalue, when I looked at
the set of variables in the shaders in the dota2 trace.  When I
saw all the built-ins, I recalled a suggestion that Eric had made about
dead-code eliminating the unused variables.

64% space reduction for ir_variable on 32-bit in the test case.