Add bswap intrinsics as documented in the Language Reference

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25309 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Intrinsics.h

@@ -58,19 +58,21 @@ namespace Intrinsic {
     dbg_func_start,   // Start of a function
     dbg_declare,      // Declare a local object
 
-
-    // Standard libc functions.
+    // Standard C library intrinsics.
     memcpy,         // Copy non-overlapping memory blocks
     memmove,        // Copy potentially overlapping memory blocks
     memset,         // Fill memory with a byte value
-
-    // libm related functions.
     isunordered,    // Return true if either argument is a NaN
-    ctpop, //count population
-    ctlz, //count leading zeros
-    cttz, //count trailing zeros
-    sqrt, //square root
+    sqrt,           // Square root
 
+    // Bit manipulation instrinsics.
+    bswap_i16,      // Byteswap 16 bits
+    bswap_i32,      // Byteswap 32 bits
+    bswap_i64,      // Byteswap 64 bits
+    ctpop,          // Count population
+    ctlz,           // Count leading zeros
+    cttz,           // Count trailing zeros
+    
     // Input/Output intrinsics.
     readport,
     writeport,

include/llvm/Support/MathExtras.h

@@ -79,6 +79,32 @@ inline bool isPowerOf2_64(uint64_t Value) {
   return Value && !(Value & (Value - 1LL));
 }
 
+// ByteSwap_16 - This function returns a byte-swapped representation of the
+// 16-bit argument, Value.
+inline unsigned short ByteSwap_16(unsigned short Value) {
+  unsigned short Hi = Value << 8;
+  unsigned short Lo = Value >> 8;
+  return Hi | Lo;
+}
+
+// ByteSwap_32 - This function returns a byte-swapped representation of the
+// 32-bit argument, Value.
+inline unsigned ByteSwap_32(unsigned Value) {
+  unsigned Byte0 = Value & 0x000000FF;
+  unsigned Byte1 = Value & 0x0000FF00;
+  unsigned Byte2 = Value & 0x00FF0000;
+  unsigned Byte3 = Value & 0xFF000000;
+  return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
+}
+
+// ByteSwap_64 - This function returns a byte-swapped representation of the
+// 64-bit argument, Value.
+inline uint64_t ByteSwap_64(uint64_t Value) {
+  uint64_t Hi = ByteSwap_32(Value);
+  uint64_t Lo = ByteSwap_32(Value >> 32);
+  return (Hi << 32) | Lo;
+}
+
 // CountLeadingZeros_32 - this function performs the platform optimal form of
 // counting the number of zeros from the most significant bit to the first one
 // bit.  Ex. CountLeadingZeros_32(0x00F000FF) == 8.