[llvm] r265763 - [TargetRegisterInfo] Fix BitMaskClassIterator::moveToNextID implementation.

[Quentin Colombet via llvm-commits]

Author: qcolombet
Date: Thu Apr  7 19:50:58 2016
New Revision: 265763

URL: http://llvm.org/viewvc/llvm-project?rev=265763&view=rev
Log:
[TargetRegisterInfo] Fix BitMaskClassIterator::moveToNextID implementation.

Make sure we do not read past the size of the mask. Although we were not using
the value read, this is bad and makes ASan complain.

Modified:
    llvm/trunk/include/llvm/Target/TargetRegisterInfo.h

Modified: llvm/trunk/include/llvm/Target/TargetRegisterInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetRegisterInfo.h?rev=265763&r1=265762&r2=265763&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetRegisterInfo.h (original)
+++ llvm/trunk/include/llvm/Target/TargetRegisterInfo.h Thu Apr  7 19:50:58 2016
@@ -987,17 +987,16 @@ class BitMaskClassIterator {
     // If the current chunk of memory is empty, move to the next one,
     // while making sure we do not go pass the number of register
     // classes.
-    while (!CurrentChunk && Base < NumRegClasses) {
+    while (!CurrentChunk) {
       // Move to the next chunk.
-      CurrentChunk = *++Mask;
       Base += 32;
+      if (Base >= NumRegClasses) {
+        ID = NumRegClasses;
+        return;
+      }
+      CurrentChunk = *++Mask;
       Idx = Base;
     }
-    // The mask is empty now.
-    if (!CurrentChunk || Base >= NumRegClasses) {
-      ID = NumRegClasses;
-      return;
-    }
     // Otherwise look for the first bit set from the right
     // (representation of the class ID is big endian).
     // See getSubClassMask for more details on the representation.