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aaecc0fc08
This optional register liveness analysis pass can be enabled with either -enable-stackmap-liveness, -enable-patchpoint-liveness, or both. The pass traverses each basic block in a machine function. For each basic block the instructions are processed in reversed order and if a patchpoint or stackmap instruction is encountered the current live-out register set is encoded as a register mask and attached to the instruction. Later on during stackmap generation the live-out register mask is processed and also emitted as part of the stackmap. This information is optional and intended for optimization purposes only. This will enable a client of the stackmap to reason about the registers it can use and which registers need to be preserved. Reviewed by Andy git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197317 91177308-0d34-0410-b5e6-96231b3b80d8