add uadd_ov/usub_ov to apint, consolidate constant folding

logic to use the new APInt methods.  Among other things this
implements rdar://8501501 - llvm.smul.with.overflow.i32 should constant fold

which comes from "clang -ftrapv", originally brought to my attention from PR8221.

llvm-svn: 116457

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index ca68988712d..3807314bac4 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -2053,6 +2053,12 @@ APInt APInt::sadd_ov(const APInt &RHS, bool &Overflow) const {
   return Res;
 }
 
+APInt APInt::uadd_ov(const APInt &RHS, bool &Overflow) const {
+  APInt Res = *this+RHS;
+  Overflow = Res.ult(RHS);
+  return Res;
+}
+
 APInt APInt::ssub_ov(const APInt &RHS, bool &Overflow) const {
   APInt Res = *this - RHS;
   Overflow = isNonNegative() != RHS.isNonNegative() &&
@@ -2060,6 +2066,12 @@ APInt APInt::ssub_ov(const APInt &RHS, bool &Overflow) const {
   return Res;
 }
 
+APInt APInt::usub_ov(const APInt &RHS, bool &Overflow) const {
+  APInt Res = *this+RHS;
+  Overflow = Res.ugt(RHS);
+  return Res;
+}
+
 APInt APInt::sdiv_ov(const APInt &RHS, bool &Overflow) const {
   // MININT/-1  -->  overflow.
   Overflow = isMinSignedValue() && RHS.isAllOnesValue();