add a few operations for signed operations that also

return an overflow flag.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116452 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/APInt.h

@@ -788,8 +788,7 @@ public:
                       APInt &Quotient, APInt &Remainder);
 
   static void sdivrem(const APInt &LHS, const APInt &RHS,
-                      APInt &Quotient, APInt &Remainder)
+                      APInt &Quotient, APInt &Remainder) {
-  {
     if (LHS.isNegative()) {
       if (RHS.isNegative())
         APInt::udivrem(-LHS, -RHS, Quotient, Remainder);
@@ -805,6 +804,16 @@ public:
     }
   }
   
+  
+  // Operations that return overflow indicators.
+  
+  // ssub_ov - Signed subtraction.  Unsigned subtraction never overflows.
+  APInt sadd_ov(const APInt &RHS, bool &Overflow);
+  APInt ssub_ov(const APInt &RHS, bool &Overflow);
+  APInt sdiv_ov(const APInt &RHS, bool &Overflow);
+  APInt smul_ov(const APInt &RHS, bool &Overflow);
+  APInt sshl_ov(unsigned Amt, bool &Overflow);
+
   /// @returns the bit value at bitPosition
   /// @brief Array-indexing support.
   bool operator[](unsigned bitPosition) const;
@@ -988,6 +997,9 @@ public:
     return sge(APInt(getBitWidth(), RHS));
   }
 
+  
+  
+  
   /// This operation tests if there are any pairs of corresponding bits
   /// between this APInt and RHS that are both set.
   bool intersects(const APInt &RHS) const {

lib/Support/APInt.cpp

@@ -2046,6 +2046,52 @@ void APInt::udivrem(const APInt &LHS, const APInt &RHS,
   divide(LHS, lhsWords, RHS, rhsWords, &Quotient, &Remainder);
 }
 
+APInt APInt::sadd_ov(const APInt &RHS, bool &Overflow) {
+  APInt Res = *this+RHS;
+  Overflow = isNonNegative() == RHS.isNonNegative() &&
+             Res.isNonNegative() != isNonNegative();
+  return Res;
+}
+
+APInt APInt::ssub_ov(const APInt &RHS, bool &Overflow) {
+  APInt Res = *this - RHS;
+  Overflow = isNonNegative() != RHS.isNonNegative() &&
+             Res.isNonNegative() != isNonNegative();
+  return Res;
+}
+
+APInt APInt::sdiv_ov(const APInt &RHS, bool &Overflow) {
+  // MININT/-1  -->  overflow.
+  Overflow = isMinSignedValue() && RHS.isAllOnesValue();
+  return sdiv(RHS);
+}
+
+APInt APInt::smul_ov(const APInt &RHS, bool &Overflow) {
+  APInt Res = *this * RHS;
+  
+  if (*this != 0 && RHS != 0)
+    Overflow = Res.sdiv(RHS) != *this || Res.sdiv(*this) != RHS;
+  else
+    Overflow = false;
+  return Res;
+}
+
+APInt APInt::sshl_ov(unsigned ShAmt, bool &Overflow) {
+  Overflow = ShAmt >= getBitWidth();
+  if (Overflow)
+    ShAmt = getBitWidth()-1;
+
+  if (isNonNegative()) // Don't allow sign change.
+    Overflow = ShAmt >= countLeadingZeros();
+  else
+    Overflow = ShAmt >= countLeadingOnes();
+  
+  return *this << ShAmt;
+}
+
+
+
+
 void APInt::fromString(unsigned numbits, StringRef str, uint8_t radix) {
   // Check our assumptions here
   assert(!str.empty() && "Invalid string length");