diff --git a/mlir/lib/IR/Attributes.cpp b/mlir/lib/IR/Attributes.cpp
--- a/mlir/lib/IR/Attributes.cpp
+++ b/mlir/lib/IR/Attributes.cpp
@@ -16,6 +16,7 @@
 #include "mlir/IR/Types.h"
 #include "llvm/ADT/Sequence.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Support/Endian.h"
 
 using namespace mlir;
 using namespace mlir::detail;
@@ -550,6 +551,29 @@
   return (rawData[bitPos / CHAR_BIT] & (1 << (bitPos % CHAR_BIT))) != 0;
 }
 
+/// Get start position of actual data in `value`. Actual data is
+/// stored in last `bitWidth`/CHAR_BIT bytes in big endian.
+static char *getAPIntDataPos(APInt &value, size_t bitWidth) {
+  char *dataPos =
+      const_cast<char *>(reinterpret_cast<const char *>(value.getRawData()));
+  if (llvm::support::endian::system_endianness() ==
+      llvm::support::endianness::big)
+    dataPos = dataPos + 8 - llvm::divideCeil(bitWidth, CHAR_BIT);
+  return dataPos;
+}
+
+/// Read APInt `value` from appropriate position.
+static void readAPInt(APInt &value, size_t bitWidth, char *outData) {
+  char *dataPos = getAPIntDataPos(value, bitWidth);
+  std::copy_n(dataPos, llvm::divideCeil(bitWidth, CHAR_BIT), outData);
+}
+
+/// Write `inData` to appropriate position of APInt `value`.
+static void writeAPInt(const char *inData, size_t bitWidth, APInt &value) {
+  char *dataPos = getAPIntDataPos(value, bitWidth);
+  std::copy_n(inData, llvm::divideCeil(bitWidth, CHAR_BIT), dataPos);
+}
+
 /// Writes value to the bit position `bitPos` in array `rawData`.
 static void writeBits(char *rawData, size_t bitPos, APInt value) {
   size_t bitWidth = value.getBitWidth();
@@ -560,9 +584,7 @@
 
   // Otherwise, the bit position is guaranteed to be byte aligned.
   assert((bitPos % CHAR_BIT) == 0 && "expected bitPos to be 8-bit aligned");
-  std::copy_n(reinterpret_cast<const char *>(value.getRawData()),
-              llvm::divideCeil(bitWidth, CHAR_BIT),
-              rawData + (bitPos / CHAR_BIT));
+  readAPInt(value, bitWidth, rawData + (bitPos / CHAR_BIT));
 }
 
 /// Reads the next `bitWidth` bits from the bit position `bitPos` in array
@@ -575,9 +597,7 @@
   // Otherwise, the bit position must be 8-bit aligned.
   assert((bitPos % CHAR_BIT) == 0 && "expected bitPos to be 8-bit aligned");
   APInt result(bitWidth, 0);
-  std::copy_n(
-      rawData + (bitPos / CHAR_BIT), llvm::divideCeil(bitWidth, CHAR_BIT),
-      const_cast<char *>(reinterpret_cast<const char *>(result.getRawData())));
+  writeAPInt(rawData + (bitPos / CHAR_BIT), bitWidth, result);
   return result;
 }