[PATCH] D61236: [NFC] Add a static function to do the endian check

[Qing Shan Zhang via Phabricator via llvm-commits]

steven.zhang updated this revision to Diff 197050.
steven.zhang marked an inline comment as done.
steven.zhang added a comment.

Update the patch according to the reviewer comments.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61236/new/

https://reviews.llvm.org/D61236

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6121,6 +6121,39 @@
   return None;
 }
 
+static unsigned LittleEndianByteAt(unsigned BW, unsigned i) {
+  return i;
+}
+
+static unsigned BigEndianByteAt(unsigned BW, unsigned i) {
+  return BW - i - 1;
+}
+
+// Check if the bytes offsets we are looking at match with either big or
+// little endian value loaded. If it returns true, the endian is set in
+// IsBigEndian, otherwise, the match failed.
+static bool matchEndian(const SmallVector<int64_t, 4> &ByteOffsets,
+                        int64_t FirstOffset, bool &IsBigEndian) {
+  // The endian can be decided only when it is 2 bytes at least.
+  unsigned Width = ByteOffsets.size();
+  if (Width < 2)
+    return false;
+
+  bool BigEndian = true, LittleEndian = true;
+  for (unsigned i = 0; i < Width; i++) {
+    int64_t CurrentByteOffset = ByteOffsets[i] - FirstOffset;
+    LittleEndian &= CurrentByteOffset == LittleEndianByteAt(Width, i);
+    BigEndian &= CurrentByteOffset == BigEndianByteAt(Width, i);
+    if (!BigEndian && !LittleEndian)
+      return false;
+  }
+
+  assert((BigEndian != LittleEndian) && "It should be either big endian or"
+                                        "little endian");
+  IsBigEndian = BigEndian;
+  return true;
+}
+
 /// Match a pattern where a wide type scalar value is loaded by several narrow
 /// loads and combined by shifts and ors. Fold it into a single load or a load
 /// and a BSWAP if the targets supports it.
@@ -6168,11 +6201,6 @@
   if (LegalOperations && !TLI.isOperationLegal(ISD::LOAD, VT))
     return SDValue();
 
-  std::function<unsigned(unsigned, unsigned)> LittleEndianByteAt = [](
-    unsigned BW, unsigned i) { return i; };
-  std::function<unsigned(unsigned, unsigned)> BigEndianByteAt = [](
-    unsigned BW, unsigned i) { return BW - i - 1; };
-
   bool IsBigEndianTarget = DAG.getDataLayout().isBigEndian();
   auto MemoryByteOffset = [&] (ByteProvider P) {
     assert(P.isMemory() && "Must be a memory byte provider");
@@ -6239,15 +6267,10 @@
 
   // Check if the bytes of the OR we are looking at match with either big or
   // little endian value load
-  bool BigEndian = true, LittleEndian = true;
-  for (unsigned i = 0; i < ByteWidth; i++) {
-    int64_t CurrentByteOffset = ByteOffsets[i] - FirstOffset;
-    LittleEndian &= CurrentByteOffset == LittleEndianByteAt(ByteWidth, i);
-    BigEndian &= CurrentByteOffset == BigEndianByteAt(ByteWidth, i);
-    if (!BigEndian && !LittleEndian)
-      return SDValue();
-  }
-  assert((BigEndian != LittleEndian) && "should be either or");
+  bool BigEndian = false;
+  if (!matchEndian(ByteOffsets, FirstOffset, BigEndian))
+    return SDValue();
+
   assert(FirstByteProvider && "must be set");
 
   // Ensure that the first byte is loaded from zero offset of the first load.


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