[llvm] [RISCV][CostModel] Correct the cost of some reductions (PR #118072)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: LiqinWeng (LiqinWeng)

<details>
<summary>Changes</summary>

Reductions include: and/or/max/min

---
Full diff: https://github.com/llvm/llvm-project/pull/118072.diff


1 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp (+13-6) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index 8f0ef69258b165..b098dd0b7613e5 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -1470,27 +1470,27 @@ RISCVTTIImpl::getMinMaxReductionCost(Intrinsic::ID IID, VectorType *Ty,
     llvm_unreachable("Unsupported intrinsic");
   case Intrinsic::smax:
     SplitOp = RISCV::VMAX_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMAX_VS, RISCV::VMV_X_S};
+    Opcodes = {RISCV::VREDMAX_VS, RISCV::VMV_X_S};
     break;
   case Intrinsic::smin:
     SplitOp = RISCV::VMIN_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMIN_VS, RISCV::VMV_X_S};
+    Opcodes = {RISCV::VREDMIN_VS, RISCV::VMV_X_S};
     break;
   case Intrinsic::umax:
     SplitOp = RISCV::VMAXU_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMAXU_VS, RISCV::VMV_X_S};
+    Opcodes = {RISCV::VREDMAXU_VS, RISCV::VMV_X_S};
     break;
   case Intrinsic::umin:
     SplitOp = RISCV::VMINU_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMINU_VS, RISCV::VMV_X_S};
+    Opcodes = {RISCV::VREDMINU_VS, RISCV::VMV_X_S};
     break;
   case Intrinsic::maxnum:
     SplitOp = RISCV::VFMAX_VV;
-    Opcodes = {RISCV::VFMV_S_F, RISCV::VFREDMAX_VS, RISCV::VFMV_F_S};
+    Opcodes = {RISCV::VFREDMAX_VS, RISCV::VFMV_F_S};
     break;
   case Intrinsic::minnum:
     SplitOp = RISCV::VFMIN_VV;
-    Opcodes = {RISCV::VFMV_S_F, RISCV::VFREDMIN_VS, RISCV::VFMV_F_S};
+    Opcodes = {RISCV::VFREDMIN_VS, RISCV::VFMV_F_S};
     break;
   }
   // Add a cost for data larger than LMUL8
@@ -1534,6 +1534,13 @@ RISCVTTIImpl::getArithmeticReductionCost(unsigned Opcode, VectorType *Ty,
              getRISCVInstructionCost(Opcodes, LT.second, CostKind) +
              getCmpSelInstrCost(Instruction::ICmp, ElementTy, ElementTy,
                                 CmpInst::ICMP_EQ, CostKind);
+    } else if (ISD == ISD::XOR) {
+      // Example sequences:
+      //   vsetvli a0, zero, e8, mf8, ta, ma
+      //   vcpop.m a0, v0
+      //   andi a0, a0, 1
+      Opcodes = {RISCV::VCPOP_M};
+      return LT.first + getRISCVInstructionCost(Opcodes, LT.second, CostKind);
     } else {
       // Example sequences:
       //   vsetvli a0, zero, e8, mf8, ta, ma

``````````

</details>


https://github.com/llvm/llvm-project/pull/118072