[PATCH] D27193: MachineLoopInfo: add function findInductionRegister.

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added inline comments.


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Comment at: include/llvm/CodeGen/MachineLoopInfo.h:174
+  ///   R = R + #bump
+  ///   if (R < #N) goto loop
+  /// IVBump is the immediate value added to R, and IVOp is the instruction
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Which register would you return in such case:
  ///   R0 = phi ..., [ R1, LatchBlock ]
  ///   R1 = R0 + #bump
  ///   if (R1 < #N) goto loop

Is this supposed to work only on non-SSA code?


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Comment at: include/llvm/CodeGen/MachineLoopInfo.h:176
+  /// IVBump is the immediate value added to R, and IVOp is the instruction
+  /// "R = R + #bump".
+  bool findInductionRegister(MachineLoop *L, unsigned &Reg, int64_t &IVBump,
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What do we do we more general representation?
E.g., R = R * 2
Or with R = R + RuntimeConstant?

Basically where I am going is shouldn't we have a representation a la SCEV?


https://reviews.llvm.org/D27193