[llvm] [DAG] Add SDPatternMatch::m_BitCast matcher (PR #123327)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/123327

Simplifies a future patch

>From a59ed76049198bc152441dd55ea5f8c2d0a086f2 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Fri, 17 Jan 2025 11:38:00 +0000
Subject: [PATCH] [DAG] Add SDPatternMatch::m_BitCast matcher

Simplifies a future patch
---
 llvm/include/llvm/CodeGen/SDPatternMatch.h              | 5 +++++
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp           | 2 +-
 llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp | 5 +++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/CodeGen/SDPatternMatch.h b/llvm/include/llvm/CodeGen/SDPatternMatch.h
index 4faa090901a6a6..5c9e829cc60e67 100644
--- a/llvm/include/llvm/CodeGen/SDPatternMatch.h
+++ b/llvm/include/llvm/CodeGen/SDPatternMatch.h
@@ -896,6 +896,11 @@ inline UnaryOpc_match<Opnd, true> m_ChainedUnaryOp(unsigned Opc,
   return UnaryOpc_match<Opnd, true>(Opc, Op);
 }
 
+template <typename Opnd>
+inline UnaryOpc_match<Opnd> m_BitCast(const Opnd &Op) {
+  return UnaryOpc_match<Opnd>(ISD::BITCAST, Op);
+}
+
 template <typename Opnd>
 inline UnaryOpc_match<Opnd> m_BSwap(const Opnd &Op) {
   return UnaryOpc_match<Opnd>(ISD::BSWAP, Op);
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index de7fb21f5903e3..49e5b7d9ef0141 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -15770,7 +15770,7 @@ SDValue DAGCombiner::foldBitcastedFPLogic(SDNode *N, SelectionDAG &DAG,
   // FIXME: I don't think looking for bitcast intrinsically makes sense, but
   // removing this would require more changes.
   auto IsBitCastOrFree = [&TLI, FPOpcode](SDValue Op, EVT VT) {
-    if (Op.getOpcode() == ISD::BITCAST && Op.getOperand(0).getValueType() == VT)
+    if (sd_match(Op, m_BitCast(m_SpecificVT(VT))))
       return true;
 
     return FPOpcode == ISD::FABS ? TLI.isFAbsFree(VT) : TLI.isFNegFree(VT);
diff --git a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
index bf9c597d8ac5e1..736a36da97f577 100644
--- a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
+++ b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
@@ -392,6 +392,7 @@ TEST_F(SelectionDAGPatternMatchTest, matchUnaryOp) {
   SDValue FPToSI = DAG->getNode(ISD::FP_TO_SINT, DL, FloatVT, Op2);
   SDValue FPToUI = DAG->getNode(ISD::FP_TO_UINT, DL, FloatVT, Op2);
 
+  SDValue Bcast = DAG->getNode(ISD::BITCAST, DL, FloatVT, Op0);
   SDValue Brev = DAG->getNode(ISD::BITREVERSE, DL, Int32VT, Op0);
   SDValue Bswap = DAG->getNode(ISD::BSWAP, DL, Int32VT, Op0);
 
@@ -423,8 +424,12 @@ TEST_F(SelectionDAGPatternMatchTest, matchUnaryOp) {
   EXPECT_FALSE(sd_match(FPToUI, m_FPToSI(m_Value())));
   EXPECT_FALSE(sd_match(FPToSI, m_FPToUI(m_Value())));
 
+  EXPECT_TRUE(sd_match(Bcast, m_BitCast(m_Value())));
+  EXPECT_TRUE(sd_match(Bcast, m_BitCast(m_SpecificVT(MVT::i32))));
   EXPECT_TRUE(sd_match(Brev, m_BitReverse(m_Value())));
   EXPECT_TRUE(sd_match(Bswap, m_BSwap(m_Value())));
+  EXPECT_FALSE(sd_match(Bcast, m_BitReverse(m_Value())));
+  EXPECT_FALSE(sd_match(Bcast, m_BitCast(m_SpecificVT(MVT::f32))));
   EXPECT_FALSE(sd_match(Brev, m_BSwap(m_Value())));
   EXPECT_FALSE(sd_match(Bswap, m_BitReverse(m_Value())));