[PATCH] D24857: [ARM] Assign cost of scaling used in addressing mode for ARM cores

[Renato Golin via llvm-commits]

rengolin added inline comments.


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Comment at: lib/Target/ARM/ARMISelLowering.cpp:11604
+  if (isLegalAddressingMode(DL, AM, Ty, AS)) {
+    if (Subtarget->hasFPAO())
+      return AM.Scale < 0 ? 1 : 0; // positive offsets execute faster
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This is not really a cost model... but I don't have a better idea. This is a very specific feature.

@jmolloy, are you happy with this?


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Comment at: lib/Target/ARM/ARMISelLowering.cpp:11608
+  }
+  return -1;
+}
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I guess -1 here means illegal, though without seeing the code that is using it, I can't assume.


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Comment at: lib/Target/ARM/ARMISelLowering.h:299
+    /// If the AM is not supported, the return value must be negative.
+    int getScalingFactorCost(const DataLayout &DL, const AddrMode &AM, Type *Ty,
+                             unsigned AS) const override;
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Where is this being used?


https://reviews.llvm.org/D24857