[PATCH] D71389: [ConstantFold][SVE] Fix constant folding for bitcast.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added a comment.

Thanks for adding the extra constant fold @huihuiz!



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Comment at: llvm/lib/IR/ConstantFold.cpp:580
+                m_ShuffleVector(
+                    m_InsertElement(m_Undef(), m_Constant(SplatV), m_Zero()),
+                    m_Value(), m_Zero()))) {
----------------
Because we're matching for a zero mask, explicitly matching `m_Undef` here seems unnecessarily restrictive, `m_Value()` should be sufficient.


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Comment at: llvm/lib/IR/ConstantFold.cpp:587
+            UndefValue::get(DestTy), NewCast,
+            cast<Constant>(InsertElem->getOperand(2)));
+        return ConstantExpr::getShuffleVector(
----------------
Can we match this value directly with `m_Zero(Zero)`, rather than needing `auto InsertElem` and `InsertElem->getOperand(2)` ?


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Comment at: llvm/lib/IR/ConstantFold.cpp:590
+            NewInsertElem,
+            ConstantExpr::getCast(opc, CE->getOperand(1), DestTy),
+            CE->getOperand(2));
----------------
Can we match the value for `CE->getOperand(1)` value directly with something like `m_Value(Vec2)`. I'd expect `CE->getOperand(2)` can reuse `Zero` as suggested above.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D71389/new/

https://reviews.llvm.org/D71389