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[CodeGen] Generic Hardware Loop Support

Description

[CodeGen] Generic Hardware Loop Support

Patch which introduces a target-independent framework for generating
hardware loops at the IR level. Most of the code has been taken from
PowerPC CTRLoops and PowerPC has been ported over to use this generic
pass. The target dependent parts have been moved into
TargetTransformInfo, via isHardwareLoopProfitable, with
HardwareLoopInfo introduced to transfer information from the backend.

Three generic intrinsics have been introduced:

  • void @llvm.set_loop_iterations Takes as a single operand, the number of iterations to be executed.
  • i1 @llvm.loop_decrement(anyint) Takes the maximum number of elements processed in an iteration of the loop body and subtracts this from the total count. Returns false when the loop should exit.
  • anyint @llvm.loop_decrement_reg(anyint, anyint) Takes the number of elements remaining to be processed as well as the maximum numbe of elements processed in an iteration of the loop body. Returns the updated number of elements remaining.

Details

Committed
sam_parkerJun 7 2019, 12:35 AM
Parents
rL362773: [AVR] Expand 16-bit rotations during the legalization stage
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