[llvm] [RISCV][CostModel] Add cost for fabs/fsqrt of type bf16/f16 (PR #118608)

[Craig Topper via llvm-commits]

================
@@ -1035,21 +1035,40 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     }
     break;
   }
-  case Intrinsic::fabs:
+  case Intrinsic::fabs: {
+    auto LT = getTypeLegalizationCost(RetTy);
+    if (ST->hasVInstructions() && LT.second.isVector()) {
+      // lui a0, 8
+      // addi a0, a0, -1
+      // vsetvli a1, zero, e16, m1, ta, ma
+      // vand.vx v8, v8, a0
+      // f16 with zvfhmin and bf16 with zvfhbmin
+      if (LT.second.getVectorElementType() == MVT::bf16 ||
+          (LT.second.getVectorElementType() == MVT::f16 &&
+           !ST->hasVInstructionsF16()))
+        return LT.first * getRISCVInstructionCost(RISCV::VAND_VX, LT.second,
+                                                  CostKind) +
+               2;
+      else
+        return LT.first *
+               getRISCVInstructionCost(RISCV::VFSGNJX_VV, LT.second, CostKind);
+    }
+    break;
+  }
   case Intrinsic::sqrt: {
     auto LT = getTypeLegalizationCost(RetTy);
-    // TODO: add f16/bf16, bf16 with zvfbfmin && f16 with zvfhmin
     if (ST->hasVInstructions() && LT.second.isVector()) {
-      unsigned Op;
-      switch (ICA.getID()) {
-      case Intrinsic::fabs:
-        Op = RISCV::VFSGNJX_VV;
-        break;
-      case Intrinsic::sqrt:
-        Op = RISCV::VFSQRT_V;
-        break;
-      }
-      return LT.first * getRISCVInstructionCost(Op, LT.second, CostKind);
+      SmallVector<unsigned, 3> Opcodes;
+      // f16 with zvfhmin and bf16 with zvfbfmin
+      if (LT.second.getVectorElementType() == MVT::bf16)
+        Opcodes = {RISCV::VFWCVTBF16_F_F_V, RISCV::VFSQRT_V,
+                   RISCV::VFNCVTBF16_F_F_W};
+      else if (LT.second.getVectorElementType() == MVT::f16 &&
+               !ST->hasVInstructionsF16())
+        Opcodes = {RISCV::VFWCVT_F_F_V, RISCV::VFSQRT_V, RISCV::VFNCVT_F_F_W};
+      else
+        Opcodes = {RISCV::VFSQRT_V};
+      return LT.first * getRISCVInstructionCost(Opcodes, LT.second, CostKind);
----------------
topperc wrote:

When widening, the cost for the VFSQRT_V needs to use the f32 type not the f16 type. The LMUL is twice as large so that needs to be accounted for.

I'm not sure what LMUL should be used for VFWCVT_F_F_V and VFNCVT_F_F_W. @lukel97 @arcbbb ?

https://github.com/llvm/llvm-project/pull/118608