Improve overflow detection in StringRef::getAsUnsignedInteger().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165038 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index 8aab4b2760e73ed37491f9549291abce50af6879..f8e9208462593eacc2d504b30a2a62279cb78ca0 100644 (file)
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -350,8 +350,8 @@ bool llvm::getAsUnsignedInteger(StringRef Str, unsigned Radix,
     unsigned long long PrevResult = Result;
     Result = Result*Radix+CharVal;
 
-    // Check for overflow.
-    if (Result < PrevResult)
+    // Check for overflow by shifting back and seeing if bits were lost.
+    if (Result/Radix < PrevResult)
       return true;
 
     Str = Str.substr(1);