Split AMDGPUSubtarget into amdgcn/r600 specific subclasses. This removes most of the static_casting of the basic codegen classes everywhere, and tries to restrict the features visible on the wrong target. llvm-svn: 273652
llvm-svn: 260494
SIFixSGPRCopies does not modify the CFG, but this was being recomputed before running SIFoldOperands. llvm-svn: 248587
llvm-svn: 239657