[PATCH] D46276: [CostModel][X86] Derive TTI costs from complete scheduling models (PR36550) (RFC)

[Andrea Di Biagio via Phabricator via llvm-commits]

andreadb added inline comments.


================
Comment at: lib/Target/X86/X86TargetTransformInfo.cpp:698-716
+    { ISD::FADD,  MVT::v8f32,   2, { X86::VADDPSYrr } },
+    { ISD::FADD,  MVT::v2f64,   1, { X86::VADDPDrr } },
+    { ISD::FADD,  MVT::v4f32,   1, { X86::VADDPSrr } },
+    { ISD::FADD,  MVT::f64,     1, { X86::VADDSDrr } },
+    { ISD::FADD,  MVT::f32,     1, { X86::VADDSSrr } },
+
+    { ISD::FSUB,  MVT::v4f64,   2, { X86::VSUBPDYrr } },
----------------
I wonder if these cost tables  could be auto-generates. For example via tablegen.

```
class CostTableTransition<MVT, list<Instruction>, int DefaultCost = 1> {...};
class CostTableEntry<ISDOpcode, list<CostTableTransition>> {...};

def FMUL : ConstTableEntry<
  ISD::FMUL,
  [
    MVT::v4f64, [ X86::VMULPDYrr ],
    MVT::v8f32, [ X86::VMULPSYrr ],
    ...
  ]>
>;
```

That being said, I am not convinced that it is a good idea to do it.
It is probably a lot of work for very little gain in return. Also, it is questionable whether tablegen descriptors would be more readable and less verbose than what you have here...



Repository:
  rL LLVM

https://reviews.llvm.org/D46276