[PATCH] D132296: [RISCV] Add cost model for compare and select instructions.

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp:730
 
-    // TODO: Add cost for fp vector compare instruction.
+    // Scalarize fp vector.
+    if ((ValTy->getScalarSizeInBits() == 16 && !ST->hasVInstructionsF16()) ||
----------------
Scalarize isn't what we're doing here.  Fix the comment.  


================
Comment at: llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp:731
+    // Scalarize fp vector.
+    if ((ValTy->getScalarSizeInBits() == 16 && !ST->hasVInstructionsF16()) ||
+        (ValTy->getScalarSizeInBits() == 32 && !ST->hasVInstructionsF32()) ||
----------------
I'm not sure about the correctness of this floating point test.  There's too many interacting extensions, and I'm not sure when these predicates get set.  Looking at the code, I think the check is right here, but I'm not sure.

@craig.topper What's your take here?

Style wise, I'd encourage you to write this as:
if (has appropriate type clause) {
  switch (VecPred)
  case OneOfMany:
  case TwoOfMany:
  ...
  case NOfMany:
    return LT.first * 1;
  };
}

Specifically, let all of the unhandled cases fall through.



Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132296/new/

https://reviews.llvm.org/D132296