[ConstraintElimination] Support add nuw.

[fhahn]

Support for this was added as part of some greater refactoring.

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

Optional<std::pair<int64_t, Value *>> decompose(Value *V) {
   }
   auto *GEP = dyn_cast<GetElementPtrInst>(V);
   if (GEP && GEP->getNumOperands() == 2 &&
       isa<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))) {
     return {{cast<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))
                  ->getSExtValue(),
              GEP->getPointerOperand()}};
   }
+
+  Value *Op0;
+  ConstantInt *CI;
+  if (match(V, m_NUWAdd(m_Value(Op0), m_ConstantInt(CI))))
+    return {{CI->getSExtValue(), Op0}};
   return {{0, V}};
 }
 
 /// Turn a condition \p CmpI into a constraint vector, using indices from \p
 /// Value2Index. If \p ShouldAdd is true, new indices are added for values not
 /// yet in \p Value2Index.
 static SmallVector<int64_t, 8>
 getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,

llvm/test/Transforms/ConstraintElimination/add-nuw.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -constraint-elimination -S %s | FileCheck %s
 
 define void @test.not.uge.ult(i8 %start, i8 %low, i8 %high) {
 ; CHECK-LABEL: @test.not.uge.ult(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ADD_PTR_I:%.*]] = add nuw i8 [[START:%.*]], 3
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i8 [[ADD_PTR_I]], [[HIGH:%.*]]
 ; CHECK-NEXT:    br i1 [[C_1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[T_0:%.*]] = icmp ult i8 [[START]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_0]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_1:%.*]] = add nuw i8 [[START]], 1
 ; CHECK-NEXT:    [[T_1:%.*]] = icmp ult i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_1]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_2:%.*]] = add nuw i8 [[START]], 2
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp ult i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_2]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_3:%.*]] = add nuw i8 [[START]], 3
 ; CHECK-NEXT:    [[T_3:%.*]] = icmp ult i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_3]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_4:%.*]] = add nuw i8 [[START]], 4
 ; CHECK-NEXT:    [[C_4:%.*]] = icmp ult i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_4]])
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %add.ptr.i = add nuw i8 %start, 3
   %c.1 = icmp uge i8 %add.ptr.i, %high

 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ADD_PTR_I:%.*]] = add nuw i8 [[START:%.*]], 3
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i8 [[ADD_PTR_I]], [[HIGH:%.*]]
 ; CHECK-NEXT:    br i1 [[C_1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[T_0:%.*]] = icmp ule i8 [[START]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_0]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_1:%.*]] = add nuw i8 [[START]], 1
 ; CHECK-NEXT:    [[T_1:%.*]] = icmp ule i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_1]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_2:%.*]] = add nuw i8 [[START]], 2
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp ule i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_2]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_3:%.*]] = add nuw i8 [[START]], 3
 ; CHECK-NEXT:    [[T_3:%.*]] = icmp ule i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_3]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_4:%.*]] = add nuw i8 [[START]], 4
 ; CHECK-NEXT:    [[T_4:%.*]] = icmp ule i8 [[START_4]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[T_4]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[START_5:%.*]] = add nuw i8 [[START]], 5
 ; CHECK-NEXT:    [[C_5:%.*]] = icmp ule i8 [[START_5]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_5]])
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %add.ptr.i = add nuw i8 %start, 3
   %c.1 = icmp uge i8 %add.ptr.i, %high

 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ADD_PTR_I:%.*]] = add nuw i8 [[START:%.*]], 3
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i8 [[ADD_PTR_I]], [[HIGH:%.*]]
 ; CHECK-NEXT:    br i1 [[C_1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[F_0:%.*]] = icmp ugt i8 [[START]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_0]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_1:%.*]] = add nuw i8 [[START]], 1
 ; CHECK-NEXT:    [[F_1:%.*]] = icmp ugt i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_1]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_2:%.*]] = add nuw i8 [[START]], 2
 ; CHECK-NEXT:    [[F_2:%.*]] = icmp ugt i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_2]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_3:%.*]] = add nuw i8 [[START]], 3
 ; CHECK-NEXT:    [[F_3:%.*]] = icmp ugt i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_3]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_4:%.*]] = add nuw i8 [[START]], 4
 ; CHECK-NEXT:    [[F_4:%.*]] = icmp ugt i8 [[START_4]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_4]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_5:%.*]] = add nuw i8 [[START]], 5
 ; CHECK-NEXT:    [[C_5:%.*]] = icmp ugt i8 [[START_5]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_5]])
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %add.ptr.i = add nuw i8 %start, 3
   %c.1 = icmp uge i8 %add.ptr.i, %high

 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ADD_PTR_I:%.*]] = add nuw i8 [[START:%.*]], 3
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i8 [[ADD_PTR_I]], [[HIGH:%.*]]
 ; CHECK-NEXT:    br i1 [[C_1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[F_0:%.*]] = icmp ugt i8 [[START]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_0]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_1:%.*]] = add nuw i8 [[START]], 1
 ; CHECK-NEXT:    [[F_1:%.*]] = icmp uge i8 [[START_1]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_1]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_2:%.*]] = add nuw i8 [[START]], 2
 ; CHECK-NEXT:    [[F_2:%.*]] = icmp uge i8 [[START_2]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_2]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_3:%.*]] = add nuw i8 [[START]], 3
 ; CHECK-NEXT:    [[F_3:%.*]] = icmp uge i8 [[START_3]], [[HIGH]]
-; CHECK-NEXT:    call void @use(i1 [[F_3]])
+; CHECK-NEXT:    call void @use(i1 false)
 ; CHECK-NEXT:    [[START_4:%.*]] = add nuw i8 [[START]], 4
 ; CHECK-NEXT:    [[C_4:%.*]] = icmp uge i8 [[START_4]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_4]])
 ; CHECK-NEXT:    [[START_5:%.*]] = add nuw i8 [[START]], 5
 ; CHECK-NEXT:    [[C_5:%.*]] = icmp uge i8 [[START_5]], [[HIGH]]
 ; CHECK-NEXT:    call void @use(i1 [[C_5]])
 ; CHECK-NEXT:    ret void
 ;