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The Hexagon schedulers need to handle instructions with a latency of 0 or 2 more accurately. The problem, in v60, is that a dependence between two instructions with a 2 cycle latency can use a .cur version of the source to achieve a 0 cycle latency when the use is in the same packet. Any othe use, must be at least 2 packets later, or a stall occurs. In other words, the compiler does not want to schedule the dependent instructions 1 cycle later. To achieve this, the latency adjustment code allows only a single dependence to have a zero latency. All other instructions have the other value, which is typically 2 cycles. We use a heuristic to determine which instruction gets the 0 latency. The Hexagon machine scheduler was also changed to increase the cost associated with 0 latency dependences than can be scheduled in the same packet. Patch by Brendon Cahoon. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275625 91177308-0d34-0410-b5e6-96231b3b80d8
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