[VPlan] Remove VPPredInstPHIRecipe::useScalars

[lukel97]

It uses the vector value of its operand if possible. Use the default definition in VPUser, which is false since onlyFirstLaneUsed is false.

From the discussion at #142594 (comment)

I don't think this is strictly NFC but I couldn't really think of a way to come up for a test case for it

[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: Luke Lau (lukel97)

Changes

It uses the vector value of its operand if possible. Use the default definition in VPUser, which is false since onlyFirstLaneUsed is false.

From the discussion at #142594 (comment)

---

Full diff: https://github.com/llvm/llvm-project/pull/143798.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/VPlan.h (-7)

diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index bbcbfee4e471b..5b8a80d5bbd21 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -2951,13 +2951,6 @@ class VPPredInstPHIRecipe : public VPSingleDefRecipe {
   void print(raw_ostream &O, const Twine &Indent,
              VPSlotTracker &SlotTracker) const override;
 #endif
-
-  /// Returns true if the recipe uses scalars of operand \p Op.
-  bool usesScalars(const VPValue *Op) const override {
-    assert(is_contained(operands(), Op) &&
-           "Op must be an operand of the recipe");
-    return true;
-  }
 };
 
 /// A common base class for widening memory operations. An optional mask can be

[fhahn]

oh so this doesn't handle the case from #142594 (comment)?

[lukel97]

oh so this doesn't handle the case from #142594 (comment)?

No it doesn't cause that broadcast to be hoisted, the scalar VP operand is already outside of the loop body.

That case in #142594 I guess just shows how the broadcast itself can be hoisted. But I don't think it's important if LICM is going to do it afterwards anyway