add a few operations for signed operations that also

return an overflow flag.

llvm-svn: 116452

1 files changed, 46 insertions, 0 deletions

diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index 8a212a291f2..51203f6091d 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/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");