[llvm-commits] [llvm] r119770 - /llvm/trunk/lib/Support/FoldingSet.cpp

[Dale Johannesen]

Author: johannes
Date: Thu Nov 18 18:48:58 2010
New Revision: 119770

URL: http://llvm.org/viewvc/llvm-project?rev=119770&view=rev
Log:
Aligned and unaligned copies of the same string
were not hashing to the same value.  Analysis
and patch by Frits van Bommel!


Modified:
    llvm/trunk/lib/Support/FoldingSet.cpp

Modified: llvm/trunk/lib/Support/FoldingSet.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/FoldingSet.cpp?rev=119770&r1=119769&r2=119770&view=diff
==============================================================================
--- llvm/trunk/lib/Support/FoldingSet.cpp (original)
+++ llvm/trunk/lib/Support/FoldingSet.cpp Thu Nov 18 18:48:58 2010
@@ -18,6 +18,7 @@
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/System/Host.h"
 #include <cassert>
 #include <cstring>
 using namespace llvm;
@@ -110,18 +111,32 @@
     Pos = (Units + 1) * 4;
   } else {
     // Otherwise do it the hard way.
-    for (Pos += 4; Pos <= Size; Pos += 4) {
-      unsigned V = ((unsigned char)String[Pos - 4] << 24) |
-                   ((unsigned char)String[Pos - 3] << 16) |
-                   ((unsigned char)String[Pos - 2] << 8) |
-                    (unsigned char)String[Pos - 1];
-      Bits.push_back(V);
+    // To be compatible with above bulk transfer, we need to take endianness
+    // into account.
+    if (sys::isBigEndianHost()) {
+      for (Pos += 4; Pos <= Size; Pos += 4) {
+        unsigned V = ((unsigned char)String[Pos - 4] << 24) |
+                     ((unsigned char)String[Pos - 3] << 16) |
+                     ((unsigned char)String[Pos - 2] << 8) |
+                      (unsigned char)String[Pos - 1];
+        Bits.push_back(V);
+      }
+    } else {
+      assert(sys::isLittleEndianHost() && "Unexpected host endianness");
+      for (Pos += 4; Pos <= Size; Pos += 4) {
+        unsigned V = ((unsigned char)String[Pos - 1] << 24) |
+                     ((unsigned char)String[Pos - 2] << 16) |
+                     ((unsigned char)String[Pos - 3] << 8) |
+                      (unsigned char)String[Pos - 4];
+        Bits.push_back(V);
+      }
     }
   }
   
   // With the leftover bits.
   unsigned V = 0;
-  // Pos will have overshot size by 4 - #bytes left over. 
+  // Pos will have overshot size by 4 - #bytes left over.
+  // No need to take endianness into account here - this is always executed.
   switch (Pos - Size) {
   case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
   case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.