[llvm] [RISCV][TTI] Refine the cost of FCmp (PR #88833)

[Yeting Kuo via llvm-commits]

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@@ -1383,28 +1385,69 @@ InstructionCost RISCVTTIImpl::getCmpSelInstrCost(unsigned Opcode, Type *ValTy,
            getRISCVInstructionCost(RISCV::VMSLT_VV, LT.second, CostKind);
   }
 
-  if ((Opcode == Instruction::FCmp) && ValTy->isVectorTy()) {
+  if ((Opcode == Instruction::FCmp) && ValTy->isVectorTy() &&
+      CmpInst::isFPPredicate(VecPred)) {
+
+    // Use VMXOR_MM and VMXNOR_MM to generate all true/false mask
+    if ((VecPred == CmpInst::FCMP_FALSE) || (VecPred == CmpInst::FCMP_TRUE))
+      return getRISCVInstructionCost(RISCV::VMXOR_MM, LT.second, CostKind);
+
     // If we do not support the input floating point vector type, use the base
     // one which will calculate as:
     // ScalarizeCost + Num * Cost for fixed vector,
     // InvalidCost for scalable vector.
-    if ((ValTy->getScalarSizeInBits() == 16 && !ST->hasVInstructionsF16()) ||
+    if ((ValTy->getScalarSizeInBits() == 16 && !ST->hasVInstructionsF16() &&
+         !ST->hasVInstructionsF16Minimal()) ||
         (ValTy->getScalarSizeInBits() == 32 && !ST->hasVInstructionsF32()) ||
         (ValTy->getScalarSizeInBits() == 64 && !ST->hasVInstructionsF64()))
       return BaseT::getCmpSelInstrCost(Opcode, ValTy, CondTy, VecPred, CostKind,
                                        I);
+
+    if ((ValTy->getScalarSizeInBits() == 16) && !ST->hasVInstructionsF16()) {
+      // pre-widening Op1 and Op2 to f32 before comparison
+      VectorType *VecF32Ty =
+          VectorType::get(Type::getDoubleTy(ValTy->getContext()),
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yetingk wrote:

Is not use `getFloatTy` for f32?

https://github.com/llvm/llvm-project/pull/88833