[llvm] r217325 - [MCJIT] Fix a bug RuntimeDyldImpl's read/writeBytesUnaligned methods.

[Lang Hames]

Author: lhames
Date: Sat Sep  6 21:05:26 2014
New Revision: 217325

URL: http://llvm.org/viewvc/llvm-project?rev=217325&view=rev
Log:
[MCJIT] Fix a bug RuntimeDyldImpl's read/writeBytesUnaligned methods.

The previous implementation was writing to the high-bytes of integers on BE
targets (when run on LE hosts).

http://llvm.org/PR20640


Modified:
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=217325&r1=217324&r2=217325&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Sat Sep  6 21:05:26 2014
@@ -398,32 +398,30 @@ unsigned RuntimeDyldImpl::computeSection
 uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
                                              unsigned Size) const {
   uint64_t Result = 0;
-  uint8_t *Dst = reinterpret_cast<uint8_t*>(&Result);
-
-  if (IsTargetLittleEndian == sys::IsLittleEndianHost) {
-    if (!sys::IsLittleEndianHost)
-      Dst += sizeof(Result) - Size;
-    memcpy(Dst, Src, Size);
-  } else {
-    Dst += Size - 1;
-    for (unsigned i = 0; i < Size; ++i)
-      *Dst-- = *Src++;
-  }
+  if (IsTargetLittleEndian) {
+    Src += Size - 1;
+    while (Size--)
+      Result = (Result << 8) | *Src--;
+  } else
+    while (Size--)
+      Result = (Result << 8) | *Src++;
 
   return Result;
 }
 
 void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
                                           unsigned Size) const {
-  uint8_t *Src = reinterpret_cast<uint8_t*>(&Value);
-  if (IsTargetLittleEndian == sys::IsLittleEndianHost) {
-    if (!sys::IsLittleEndianHost)
-      Src += sizeof(Value) - Size;
-    memcpy(Dst, Src, Size);
+  if (IsTargetLittleEndian) {
+    while (Size--) {
+      *Dst++ = Value & 0xFF;
+      Value >>= 8;
+    }
   } else {
-    Src += Size - 1;
-    for (unsigned i = 0; i < Size; ++i)
-      *Dst++ = *Src--;
+    Dst += Size - 1;
+    while (Size--) {
+      *Dst-- = Value & 0xFF;
+      Value >>= 8;
+    }
   }
 }