[llvm] [PowerPC] adjust cost for vector insert/extract with non const index (PR #79092)

[via llvm-commits]

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@@ -697,39 +697,51 @@ InstructionCost PPCTTIImpl::getVectorInstrCost(unsigned Opcode, Type *Val,
 
     return Cost;
 
-  } else if (Val->getScalarType()->isIntegerTy() && Index != -1U) {
+  } else if (Val->getScalarType()->isIntegerTy()) {
     unsigned EltSize = Val->getScalarSizeInBits();
     // Computing on 1 bit values requires extra mask or compare operations.
-    unsigned MaskCost = VecMaskCost && EltSize == 1 ? 1 : 0;
+    unsigned MaskCostForOneBitSize = (VecMaskCost && EltSize == 1) ? 1 : 0;
+    // Computing on non const index requires extra mask or compare operations.
+    unsigned MaskCostForIdx = (Index != -1U) ? 0 : 1;
     if (ST->hasP9Altivec()) {
-      if (ISD == ISD::INSERT_VECTOR_ELT)
-        // A move-to VSR and a permute/insert.  Assume vector operation cost
-        // for both (cost will be 2x on P9).
-        return 2 * CostFactor;
-
-      // It's an extract.  Maybe we can do a cheap move-from VSR.
-      unsigned EltSize = Val->getScalarSizeInBits();
-      if (EltSize == 64) {
-        unsigned MfvsrdIndex = ST->isLittleEndian() ? 1 : 0;
-        if (Index == MfvsrdIndex)
-          return 1;
-      } else if (EltSize == 32) {
-        unsigned MfvsrwzIndex = ST->isLittleEndian() ? 2 : 1;
-        if (Index == MfvsrwzIndex)
-          return 1;
-      }
-
-      // We need a vector extract (or mfvsrld).  Assume vector operation cost.
-      // The cost of the load constant for a vector extract is disregarded
-      // (invariant, easily schedulable).
-      return CostFactor + MaskCost;
+      // P10 has vxform insert which can handle non const index. The MaskCost is
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RolandF77 wrote:

nit: MaskCost => maskCostForIdx

https://github.com/llvm/llvm-project/pull/79092