[PATCH] [Support] fix the ULEB128 decoding bug.

[Alex Lorenz]

Hi bob.wilson, bogner, dexonsmith,

This patch fixes the ULEB128 decoding which currently overflows when evaluating (*p & 0x7f) << Shift were *p = 0x10 and Shift is 28.

http://reviews.llvm.org/D5029

Files:
  include/llvm/Support/LEB128.h
  unittests/Support/LEB128Test.cpp

Index: include/llvm/Support/LEB128.h
===================================================================
--- include/llvm/Support/LEB128.h
+++ include/llvm/Support/LEB128.h
@@ -82,7 +82,7 @@
   uint64_t Value = 0;
   unsigned Shift = 0;
   do {
-    Value += (*p & 0x7f) << Shift;
+    Value += uint64_t(*p & 0x7f) << Shift;
     Shift += 7;
   } while (*p++ >= 128);
   if (n)
Index: unittests/Support/LEB128Test.cpp
===================================================================
--- unittests/Support/LEB128Test.cpp
+++ unittests/Support/LEB128Test.cpp
@@ -106,6 +106,7 @@
   EXPECT_DECODE_ULEB128_EQ(0xffu, "\xff\x01");
   EXPECT_DECODE_ULEB128_EQ(0x100u, "\x80\x02");
   EXPECT_DECODE_ULEB128_EQ(0x101u, "\x81\x02");
+  EXPECT_DECODE_ULEB128_EQ(4294975616ULL, "\x80\xc1\x80\x80\x10");
 
   // Decode ULEB128 with extra padding bytes
   EXPECT_DECODE_ULEB128_EQ(0u, "\x80\x00");
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