[PATCH] D137423: [PowerPC][WIP] make expensive mflr be awfy from its user in the function prologue

[Roland Froese via Phabricator via llvm-commits]

RolandF added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCFrameLowering.cpp:621
+  // expensive. We need to consider the latency when backup lr in the prologue.
+  const bool IsCheapMFLR = Subtarget.isISA3_1();
+
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The cost of an mflr is a characteristic of an implementation, not of the architecture.  A future processor might have a slow mflr.  I think a new subtarget feature is needed for this.


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  https://reviews.llvm.org/D137423/new/

https://reviews.llvm.org/D137423