[LVI][CVP] Add support for saturating add/sub

Adds support for the uadd.sat family of intrinsics in LVI, based on
ConstantRange methods from D60946.

Differential Revision: https://reviews.llvm.org/D62447

llvm-svn: 361703

Author: nikic

llvm/lib/Analysis/LazyValueInfo.cpp

@@ -432,6 +432,8 @@ namespace {
                            BasicBlock *BB);
   bool solveBlockValueOverflowIntrinsic(
       ValueLatticeElement &BBLV, WithOverflowInst *WO, BasicBlock *BB);
+  bool solveBlockValueIntrinsic(ValueLatticeElement &BBLV, IntrinsicInst *II,
+                                BasicBlock *BB);
   void intersectAssumeOrGuardBlockValueConstantRange(Value *Val,
                                                      ValueLatticeElement &BBLV,
                                                      Instruction *BBI);
@@ -649,6 +651,9 @@ bool LazyValueInfoImpl::solveBlockValueImpl(ValueLatticeElement &Res,
       if (auto *WO = dyn_cast<WithOverflowInst>(EVI->getAggregateOperand()))
         if (EVI->getNumIndices() == 1 && *EVI->idx_begin() == 0)
           return solveBlockValueOverflowIntrinsic(Res, WO, BB);
+
+    if (auto *II = dyn_cast<IntrinsicInst>(BBI))
+      return solveBlockValueIntrinsic(Res, II, BB);
   }
 
   LLVM_DEBUG(dbgs() << " compute BB '" << BB->getName()
@@ -1112,6 +1117,37 @@ bool LazyValueInfoImpl::solveBlockValueOverflowIntrinsic(
       });
 }
 
+bool LazyValueInfoImpl::solveBlockValueIntrinsic(
+    ValueLatticeElement &BBLV, IntrinsicInst *II, BasicBlock *BB) {
+  switch (II->getIntrinsicID()) {
+  case Intrinsic::uadd_sat:
+    return solveBlockValueBinaryOpImpl(BBLV, II, BB,
+        [](const ConstantRange &CR1, const ConstantRange &CR2) {
+          return CR1.uadd_sat(CR2);
+        });
+  case Intrinsic::usub_sat:
+    return solveBlockValueBinaryOpImpl(BBLV, II, BB,
+        [](const ConstantRange &CR1, const ConstantRange &CR2) {
+          return CR1.usub_sat(CR2);
+        });
+  case Intrinsic::sadd_sat:
+    return solveBlockValueBinaryOpImpl(BBLV, II, BB,
+        [](const ConstantRange &CR1, const ConstantRange &CR2) {
+          return CR1.sadd_sat(CR2);
+        });
+  case Intrinsic::ssub_sat:
+    return solveBlockValueBinaryOpImpl(BBLV, II, BB,
+        [](const ConstantRange &CR1, const ConstantRange &CR2) {
+          return CR1.ssub_sat(CR2);
+        });
+  default:
+    LLVM_DEBUG(dbgs() << " compute BB '" << BB->getName()
+                      << "' - overdefined (unknown intrinsic).\n");
+    BBLV = ValueLatticeElement::getOverdefined();
+    return true;
+  }
+}
+
 static ValueLatticeElement getValueFromICmpCondition(Value *Val, ICmpInst *ICI,
                                                      bool isTrueDest) {
   Value *LHS = ICI->getOperand(0);

llvm/test/Transforms/CorrelatedValuePropagation/basic.ll

@@ -995,7 +995,7 @@ define i1 @uadd_sat_unknown(i32 %a) {
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp ugt i32 [[VAL]], 100
 ; CHECK-NEXT:    br i1 undef, label [[EXIT1:%.*]], label [[EXIT2:%.*]]
 ; CHECK:       exit1:
-; CHECK-NEXT:    ret i1 [[CMP1]]
+; CHECK-NEXT:    ret i1 true
 ; CHECK:       exit2:
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
@@ -1018,7 +1018,7 @@ define i1 @usub_sat_unknown(i32 %a) {
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i32 [[VAL]], -101
 ; CHECK-NEXT:    br i1 undef, label [[EXIT1:%.*]], label [[EXIT2:%.*]]
 ; CHECK:       exit1:
-; CHECK-NEXT:    ret i1 [[CMP1]]
+; CHECK-NEXT:    ret i1 true
 ; CHECK:       exit2:
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
@@ -1041,7 +1041,7 @@ define i1 @sadd_sat_unknown(i32 %a) {
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 [[VAL]], -2147483548
 ; CHECK-NEXT:    br i1 undef, label [[EXIT1:%.*]], label [[EXIT2:%.*]]
 ; CHECK:       exit1:
-; CHECK-NEXT:    ret i1 [[CMP1]]
+; CHECK-NEXT:    ret i1 true
 ; CHECK:       exit2:
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;
@@ -1064,7 +1064,7 @@ define i1 @ssub_sat_unknown(i32 %a) {
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i32 [[VAL]], 2147483547
 ; CHECK-NEXT:    br i1 undef, label [[EXIT1:%.*]], label [[EXIT2:%.*]]
 ; CHECK:       exit1:
-; CHECK-NEXT:    ret i1 [[CMP1]]
+; CHECK-NEXT:    ret i1 true
 ; CHECK:       exit2:
 ; CHECK-NEXT:    ret i1 [[CMP2]]
 ;