From 871b4e101cb1cc0d8b99dd6bdb975592aae6da70 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 4 Apr 2007 06:36:34 +0000
Subject: [PATCH] Minor enhancements to GetIntegerValue(APInt):   * Detect
 overflow correctly.  When it occurs, return the truncated value.   * Add
 fixme for radix analysis.

llvm-svn: 39382
---
 clang/Lex/LiteralSupport.cpp             | 29 +++++++++++++++++-------
 clang/include/clang/Lex/LiteralSupport.h |  8 ++++++-
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/clang/Lex/LiteralSupport.cpp b/clang/Lex/LiteralSupport.cpp
index 286bcf6a3b09..944030f8c5a3 100644
--- a/clang/Lex/LiteralSupport.cpp
+++ b/clang/Lex/LiteralSupport.cpp
@@ -266,32 +266,45 @@ bool NumericLiteralParser::GetIntegerValue(int &val) {
 }
 
 /// GetIntegerValue - Convert this numeric literal value to an APInt that
-/// matches Val's input width.  If there is an overflow, saturate Val to zero
-/// and return false.  Otherwise, set Val and return true.
+/// matches Val's input width.  If there is an overflow, set Val to the low bits
+/// of the result and return true.  Otherwise, return false.
 bool NumericLiteralParser::GetIntegerValue(APInt &Val) {
   Val = 0;
   s = DigitsBegin;
 
-  // FIXME: This doesn't handle sign right, doesn't autopromote to wider
-  // integer, and is generally not conformant.
   APInt RadixVal(Val.getBitWidth(), radix);
   APInt CharVal(Val.getBitWidth(), 0);
   APInt OldVal = Val;
+  
+  bool OverflowOccurred = false;
   while (s < SuffixBegin) {
     unsigned C = HexLetterToVal(*s++);
     
     // If this letter is out of bound for this radix, reject it.
-    if (C >= radix) { Val = 0; return false; }
+    if (C >= radix) {
+      // FIXME: This is an error, not a warning.  This should be caught by
+      // NumericLiteralParser ctor.
+      C = C % radix;
+      OverflowOccurred = true;
+    }
     
     CharVal = C;
     
+    // Add the digit to the value in the appropriate radix.  If adding in digits
+    // made the value smaller, then this overflowed.
     OldVal = Val;
+
+    // Multiply by radix, did overflow occur on the multiply?
     Val *= RadixVal;
+    OverflowOccurred |= Val.udiv(RadixVal) != OldVal;
+
+    OldVal = Val;
+    // Add value, did overflow occur on the value?
     Val += CharVal;
-    if (OldVal.ugt(Val))
-      return false; // Overflow!
+    OverflowOccurred |= Val.ult(OldVal);
+    OverflowOccurred |= Val.ult(CharVal);
   }
-  return true;
+  return OverflowOccurred;
 }
 
 
diff --git a/clang/include/clang/Lex/LiteralSupport.h b/clang/include/clang/Lex/LiteralSupport.h
index ce134b427d78..b5b635a7ccc2 100644
--- a/clang/include/clang/Lex/LiteralSupport.h
+++ b/clang/include/clang/Lex/LiteralSupport.h
@@ -63,9 +63,15 @@ public:
   /// type (int, unsigned, long, unsigned long, long long, unsigned long long) 
   /// will be done elsewhere - the size computation is target dependent. We  
   /// return true if the value fit into "val", false otherwise. 
+  /// NOTE: The api of these returns an inverted value for 'overflow' than the
+  /// version below does.
   bool GetIntegerValue(uintmax_t &val);
   bool GetIntegerValue(int &val);
-  bool GetIntegerValue(APInt &Val);  //< Return the same width as Val.
+  
+  /// GetIntegerValue - Convert this numeric literal value to an APInt that
+  /// matches Val's input width.  If there is an overflow, set Val to the low
+  /// bits of the result and return true.  Otherwise, return false.
+  bool GetIntegerValue(APInt &Val);
 
 private:  
   void Diag(SourceLocation Loc, unsigned DiagID,