[llvm] [VPlan] Introduce explicit broadcasts for live-ins. (PR #124644)

[via llvm-commits]

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@@ -1873,6 +1888,13 @@ class VPWidenIntOrFpInductionRecipe : public VPWidenInductionRecipe {
   VPValue *getLastUnrolledPartOperand() {
     return getNumOperands() == 5 ? getOperand(4) : this;
   }
+
+  /// Returns true if the recipe only uses the first lane of operand \p Op.
+  bool onlyFirstLaneUsed(const VPValue *Op) const override {
+    assert(is_contained(operands(), Op) &&
+           "Op must be an operand of the recipe");
+    return Op == getStartValue();
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ayalz wrote:

Should this be the default for all VPHeaderPhiRecipes?

https://github.com/llvm/llvm-project/pull/124644