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
@@ -546,25 +546,57 @@
 
 /// 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) {
+static char *getAPIntDataPosBE(APInt &value, size_t bitWidth, size_t wordNum) {
   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);
+  unsigned apintBytesPerWord = APInt::APINT_BITS_PER_WORD / CHAR_BIT;
+
+  dataPos = dataPos + apintBytesPerWord * wordNum -
+            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);
+  char *dataPos =
+      const_cast<char *>(reinterpret_cast<const char *>(value.getRawData()));
+  if (llvm::support::endian::system_endianness() ==
+      llvm::support::endianness::big) {
+    unsigned numFilledWords = bitWidth / APInt::APINT_BITS_PER_WORD;
+    unsigned resBits = bitWidth - numFilledWords * APInt::APINT_BITS_PER_WORD;
+    unsigned apintBytesPerWord = APInt::APINT_BITS_PER_WORD / CHAR_BIT;
+    // Read words filled with 8 bytes data (multiple of `APINT_BITS_PER_WORD`
+    // bits)
+    std::copy_n(dataPos, apintBytesPerWord * numFilledWords, outData);
+    // Then, read the rest bits from apropriate position in big endian
+    dataPos = getAPIntDataPosBE(value, resBits, numFilledWords + 1);
+    std::copy_n(dataPos, llvm::divideCeil(resBits, CHAR_BIT),
+                outData + apintBytesPerWord * numFilledWords);
+  } else {
+    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);
+  char *dataPos =
+      const_cast<char *>(reinterpret_cast<const char *>(value.getRawData()));
+  if (llvm::support::endian::system_endianness() ==
+      llvm::support::endianness::big) {
+    unsigned numFilledWords = bitWidth / APInt::APINT_BITS_PER_WORD;
+    unsigned resBits = bitWidth - numFilledWords * APInt::APINT_BITS_PER_WORD;
+    unsigned apintBytesPerWord = APInt::APINT_BITS_PER_WORD / CHAR_BIT;
+    // Write words filled with 8 bytes data (multiple of `APINT_BITS_PER_WORD`
+    // bits)
+    std::copy_n(inData, apintBytesPerWord * numFilledWords, dataPos);
+    // Then, write the rest bits from apropriate position in big endian
+    dataPos = getAPIntDataPosBE(value, resBits, numFilledWords + 1);
+    std::copy_n(inData + apintBytesPerWord * numFilledWords,
+                llvm::divideCeil(resBits, CHAR_BIT), dataPos);
+  } else {
+    std::copy_n(inData, llvm::divideCeil(bitWidth, CHAR_BIT), dataPos);
+  }
 }
 
 /// Writes value to the bit position `bitPos` in array `rawData`.