[llvm] [SLP] More accurately cost RISCV scalar splats (PR #213104)

[Alexey Bataev via llvm-commits]

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@@ -666,6 +666,31 @@ TargetTransformInfo::getVectorInstrContextHint(const Instruction *I) {
   return VectorInstrContext::None;
 }
 
+TargetTransformInfo::VectorInstrContext
+TargetTransformInfo::getBuildVectorContextHint(
+    ArrayRef<int> Mask, ArrayRef<Value *> Scalars,
+    function_ref<bool(SmallVectorImpl<BuildVectorUseOp> &)> GatherUseOps)
+    const {
+  if (Scalars.empty() ||
+      !ShuffleVectorInst::isZeroEltSplatMask(Mask, Mask.size()))
+    return VectorInstrContext::None;
+
+  Value *SplatVal = Scalars.front();
+  if (isa<VectorType>(SplatVal->getType()) || isa<ExtractElementInst>(SplatVal))
+    return VectorInstrContext::None;
+
+  SmallVector<BuildVectorUseOp, 4> UserOps;
+  if (!GatherUseOps(UserOps) || UserOps.empty())
+    return VectorInstrContext::None;
+
+  if (all_of(UserOps, [this](const BuildVectorUseOp &UserOp) {
+        return canSplatOperand(UserOp.Opcode, UserOp.OperandIndex);
+      }))
+    return VectorInstrContext::SplatOpFolded;
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alexey-bataev wrote:

Can it be hidden in the predicate function too? In this case canSplatOperand can be removed completely

https://github.com/llvm/llvm-project/pull/213104