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

include/llvm/ADT/APInt.h

@@ -806,10 +806,10 @@ public:
   
   
   // Operations that return overflow indicators.
-  
-  // ssub_ov - Signed subtraction.  Unsigned subtraction never overflows.
   APInt sadd_ov(const APInt &RHS, bool &Overflow) const;
+  APInt uadd_ov(const APInt &RHS, bool &Overflow) const;
   APInt ssub_ov(const APInt &RHS, bool &Overflow) const;
+  APInt usub_ov(const APInt &RHS, bool &Overflow) const;
   APInt sdiv_ov(const APInt &RHS, bool &Overflow) const;
   APInt smul_ov(const APInt &RHS, bool &Overflow) const;
   APInt sshl_ov(unsigned Amt, bool &Overflow) const;

lib/Analysis/ConstantFolding.cpp

@@ -1001,6 +1001,7 @@ llvm::canConstantFoldCallTo(const Function *F) {
   case Intrinsic::usub_with_overflow:
   case Intrinsic::sadd_with_overflow:
   case Intrinsic::ssub_with_overflow:
+  case Intrinsic::smul_with_overflow:
   case Intrinsic::convert_from_fp16:
   case Intrinsic::convert_to_fp16:
     return true;
@@ -1248,42 +1249,37 @@ llvm::ConstantFoldCall(Function *F,
       if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
         switch (F->getIntrinsicID()) {
         default: break;
-        case Intrinsic::uadd_with_overflow: {
+        case Intrinsic::sadd_with_overflow:
-          Constant *Res = ConstantExpr::getAdd(Op1, Op2);           // result.
+        case Intrinsic::uadd_with_overflow:
+        case Intrinsic::ssub_with_overflow:
+        case Intrinsic::usub_with_overflow:
+        case Intrinsic::smul_with_overflow: {
+          APInt Res;
+          bool Overflow;
+          switch (F->getIntrinsicID()) {
+          default: assert(0 && "Invalid case");
+          case Intrinsic::sadd_with_overflow:
+            Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow);
+            break;
+          case Intrinsic::uadd_with_overflow:
+            Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow);
+            break;
+          case Intrinsic::ssub_with_overflow:
+            Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow);
+            break;
+          case Intrinsic::usub_with_overflow:
+            Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow);
+            break;
+          case Intrinsic::smul_with_overflow:
+            Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow);
+            break;
+          }
           Constant *Ops[] = {
-            Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
+            ConstantInt::get(F->getContext(), Res),
+            ConstantInt::get(Type::getInt1Ty(F->getContext()), Overflow)
           };
           return ConstantStruct::get(F->getContext(), Ops, 2, false);
         }
-        case Intrinsic::usub_with_overflow: {
-          Constant *Res = ConstantExpr::getSub(Op1, Op2);           // result.
-          Constant *Ops[] = {
-            Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
-          };
-          return ConstantStruct::get(F->getContext(), Ops, 2, false);
-        }
-        case Intrinsic::sadd_with_overflow: {
-          Constant *Res = ConstantExpr::getAdd(Op1, Op2);           // result.
-          Constant *Overflow = ConstantExpr::getSelect(
-              ConstantExpr::getICmp(CmpInst::ICMP_SGT,
-                ConstantInt::get(Op1->getType(), 0), Op1),
-              ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2), 
-              ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
-
-          Constant *Ops[] = { Res, Overflow };
-          return ConstantStruct::get(F->getContext(), Ops, 2, false);
-        }
-        case Intrinsic::ssub_with_overflow: {
-          Constant *Res = ConstantExpr::getSub(Op1, Op2);           // result.
-          Constant *Overflow = ConstantExpr::getSelect(
-              ConstantExpr::getICmp(CmpInst::ICMP_SGT,
-                ConstantInt::get(Op2->getType(), 0), Op2),
-              ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1), 
-              ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
-
-          Constant *Ops[] = { Res, Overflow };
-          return ConstantStruct::get(F->getContext(), Ops, 2, false);
-        }
         }
       }
       

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();

test/Transforms/ConstProp/overflow-ops.ll

@@ -170,3 +170,14 @@ declare {i8, i1} @llvm.usub.with.overflow.i8(i8, i8)
 
 declare {i8, i1} @llvm.sadd.with.overflow.i8(i8, i8)
 declare {i8, i1} @llvm.ssub.with.overflow.i8(i8, i8)
+declare {i8, i1} @llvm.smul.with.overflow.i8(i8, i8)
+
+; rdar://8501501
+define {i8, i1} @smul_1() nounwind {
+entry:
+  %t = call {i8, i1} @llvm.smul.with.overflow.i8(i8 -20, i8 -10)
+  ret {i8, i1} %t
+
+; CHECK: @smul_1
+; CHECK: ret %i8i1 { i8 -56, i1 true }
+}