[llvm] [SelectionDAG][NFC] Refactor duplicate code into SDNode::bitcastToAPInt() (PR #127503)

[Piotr Fusik via llvm-commits]

https://github.com/pfusik created https://github.com/llvm/llvm-project/pull/127503

None

>From 0e45daae938a2e20832cb8169473da53f629d7ff Mon Sep 17 00:00:00 2001
From: Piotr Fusik <p.fusik at samsung.com>
Date: Mon, 17 Feb 2025 15:48:12 +0100
Subject: [PATCH] [SelectionDAG][NFC] Refactor duplicate code into
 SDNode::bitcastToAPInt()

---
 llvm/include/llvm/CodeGen/SelectionDAGNodes.h | 10 +++++
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  6 +--
 .../lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 38 ++++++-------------
 3 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
index 6eff6bfe8d5b1..75c4fabe03dd4 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -989,6 +989,8 @@ END_TWO_BYTE_PACK()
   /// Helper method returns the APInt value of a ConstantSDNode.
   inline const APInt &getAsAPIntVal() const;
 
+  inline std::optional<APInt> bitcastToAPInt() const;
+
   const SDValue &getOperand(unsigned Num) const {
     assert(Num < NumOperands && "Invalid child # of SDNode!");
     return OperandList[Num];
@@ -1785,6 +1787,14 @@ class ConstantFPSDNode : public SDNode {
   }
 };
 
+std::optional<APInt> SDNode::bitcastToAPInt() const {
+  if (auto *CN = dyn_cast<ConstantSDNode>(this))
+    return CN->getAPIntValue();
+  if (auto *CFPN = dyn_cast<ConstantFPSDNode>(this))
+    return CFPN->getValueAPF().bitcastToAPInt();
+  return std::nullopt;
+}
+
 /// Returns true if \p V is a constant integer zero.
 bool isNullConstant(SDValue V);
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c6fd72b6b76f4..59f5d15cfed30 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -27420,10 +27420,8 @@ SDValue DAGCombiner::XformToShuffleWithZero(SDNode *N) {
       }
 
       APInt Bits;
-      if (auto *Cst = dyn_cast<ConstantSDNode>(Elt))
-        Bits = Cst->getAPIntValue();
-      else if (auto *CstFP = dyn_cast<ConstantFPSDNode>(Elt))
-        Bits = CstFP->getValueAPF().bitcastToAPInt();
+      if (auto OptBits = Elt->bitcastToAPInt())
+        Bits = *std::move(OptBits);
       else
         return SDValue();
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 9d2f87497d6fa..531314c5bfd07 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -152,14 +152,10 @@ bool ConstantFPSDNode::isValueValidForType(EVT VT,
 
 bool ISD::isConstantSplatVector(const SDNode *N, APInt &SplatVal) {
   if (N->getOpcode() == ISD::SPLAT_VECTOR) {
-    unsigned EltSize =
-        N->getValueType(0).getVectorElementType().getSizeInBits();
-    if (auto *Op0 = dyn_cast<ConstantSDNode>(N->getOperand(0))) {
-      SplatVal = Op0->getAPIntValue().trunc(EltSize);
-      return true;
-    }
-    if (auto *Op0 = dyn_cast<ConstantFPSDNode>(N->getOperand(0))) {
-      SplatVal = Op0->getValueAPF().bitcastToAPInt().trunc(EltSize);
+    if (auto OptAPInt = N->getOperand(0)->bitcastToAPInt()) {
+      unsigned EltSize =
+          N->getValueType(0).getVectorElementType().getSizeInBits();
+      SplatVal = OptAPInt->trunc(EltSize);
       return true;
     }
   }
@@ -215,12 +211,9 @@ bool ISD::isConstantSplatVectorAllOnes(const SDNode *N, bool BuildVectorOnly) {
   // we care if the resultant vector is all ones, not whether the individual
   // constants are.
   SDValue NotZero = N->getOperand(i);
-  unsigned EltSize = N->getValueType(0).getScalarSizeInBits();
-  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(NotZero)) {
-    if (CN->getAPIntValue().countr_one() < EltSize)
-      return false;
-  } else if (ConstantFPSDNode *CFPN = dyn_cast<ConstantFPSDNode>(NotZero)) {
-    if (CFPN->getValueAPF().bitcastToAPInt().countr_one() < EltSize)
+  if (auto OptAPInt = NotZero->bitcastToAPInt()) {
+    unsigned EltSize = N->getValueType(0).getScalarSizeInBits();
+    if (OptAPInt->countr_one() < EltSize)
       return false;
   } else
     return false;
@@ -259,12 +252,9 @@ bool ISD::isConstantSplatVectorAllZeros(const SDNode *N, bool BuildVectorOnly) {
     // We only want to check enough bits to cover the vector elements, because
     // we care if the resultant vector is all zeros, not whether the individual
     // constants are.
-    unsigned EltSize = N->getValueType(0).getScalarSizeInBits();
-    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Op)) {
-      if (CN->getAPIntValue().countr_zero() < EltSize)
-        return false;
-    } else if (ConstantFPSDNode *CFPN = dyn_cast<ConstantFPSDNode>(Op)) {
-      if (CFPN->getValueAPF().bitcastToAPInt().countr_zero() < EltSize)
+    if (auto OptAPInt = Op->bitcastToAPInt()) {
+      unsigned EltSize = N->getValueType(0).getScalarSizeInBits();
+      if (OptAPInt->countr_zero() < EltSize)
         return false;
     } else
       return false;
@@ -3434,13 +3424,9 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
 
   KnownBits Known(BitWidth);   // Don't know anything.
 
-  if (auto *C = dyn_cast<ConstantSDNode>(Op)) {
+  if (auto OptAPInt = Op->bitcastToAPInt()) {
     // We know all of the bits for a constant!
-    return KnownBits::makeConstant(C->getAPIntValue());
-  }
-  if (auto *C = dyn_cast<ConstantFPSDNode>(Op)) {
-    // We know all of the bits for a constant fp!
-    return KnownBits::makeConstant(C->getValueAPF().bitcastToAPInt());
+    return KnownBits::makeConstant(*std::move(OptAPInt));
   }
 
   if (Depth >= MaxRecursionDepth)