[llvm] [LV] Support EVL for partial reduction and VPExpressionRecipe. (PR #205741)

[Mel Chen via llvm-commits]

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@@ -3594,8 +3614,23 @@ void VPExpressionRecipe::printRecipe(raw_ostream &O, const Twine &Indent,
   O << " = ";
   auto *Red = cast<VPReductionRecipe>(ExpressionRecipes.back());
   unsigned Opcode = RecurrenceDescriptor::getOpcode(Red->getRecurrenceKind());
-  VPValue *RdxStart =
-      getOperand(getNumOperands() - (Red->isConditional() ? 2 : 1));
+  VPValue *Mask = getOperand(getNumOperands() - 1);
+  VPValue *EVL =
+      isa<VPReductionEVLRecipe>(Red)
+          ? getOperand(getNumOperands() - (Red->isConditional() ? 2 : 1))
+          : nullptr;
+  VPValue *RdxStart = getOperand(
+      getNumOperands() - (Red->isConditional() ? 2 : 1) - (EVL ? 1 : 0));
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Mel-Chen wrote:

Is it possible to use getChainOp() and look up LiveInPlaceholders to find out which operand position RdxStart is?

https://github.com/llvm/llvm-project/pull/205741