SimplifyCFG: don't remove unreachable default switch destinations An unreachable default destination can be exploited by other optimizations and allows for more efficient lowering. Both the SDag switch lowering and LowerSwitch can exploit unreachable defaults. Also make TurnSwitchRangeICmp handle switches with unreachable default. This is kind of separate change, but it cannot be tested without the change above, and I don't want to land the change above without this since that would regress other tests. Differential Revision: http://reviews.llvm.org/D6471 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227125 91177308-0d34-0410-b5e6-96231b3b80d8
Switch to select optimization for two-case switches This is the same optimization of r219233 with modifications to support PHIs with multiple incoming edges from the same block and a test to check that this condition is handled. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219656 91177308-0d34-0410-b5e6-96231b3b80d8
Revert r219223, it creates invalid PHI nodes. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219587 91177308-0d34-0410-b5e6-96231b3b80d8
Two case switch to select optimization This optimization tries to convert switch instructions that are used to select a value with only 2 unique cases + default block to a select or a couple of selects (depending if the default block is reachable or not). The typical case this optimization wants to be able to optimize is this one: Example: switch (a) { case 10: %0 = icmp eq i32 %a, 10 return 10; %1 = select i1 %0, i32 10, i32 4 case 20: ----> %2 = icmp eq i32 %a, 20 return 2; %3 = select i1 %2, i32 2, i32 %1 default: return 4; } It also sets the base for further optimizations that are planned and being reviewed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219223 91177308-0d34-0410-b5e6-96231b3b80d8