test/gtest/constraint.cpp

#include "ir/constraint.h"
#include "ir/abstract.h"
#include "gtest/gtest.h"

using namespace wasm;
using namespace wasm::Abstract;
using namespace wasm::constraint;

TEST(ConstraintTest, TestEq) {
  // x == 5 (we use "x" for the name of the thing being compared, in these
  // comments).
  Constraint c{Eq, {Literal(int32_t(5))}};

  // Sets start as proving anything, as representing unreachable code.
  AndedConstraintSet s;
  EXPECT_TRUE(s.provesEverything());
  EXPECT_EQ(s.proves(c), True);

  // We can't infer anything if told so.
  s.setProvesNothing();
  EXPECT_EQ(s.proves(c), Unknown);

  // If we add it, then things check out: a thing always proves itself true.
  s.approximateAnd(c);
  EXPECT_EQ(s.size(), 1);
  EXPECT_EQ(s.proves(c), True);

  // Ditto using set();
  s.set(c);
  EXPECT_EQ(s.proves(c), True);

  // x == 10, a different number: we can infer false.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(10))}}), False);

  // x != 15: we can infer true.
  EXPECT_EQ(s.proves(Constraint{Ne, {Literal(int32_t(15))}}), True);

  // x != 5: we can infer false.
  EXPECT_EQ(s.proves(Constraint{Ne, {Literal(int32_t(5))}}), False);
}

TEST(ConstraintTest, TestNe) {
  AndedConstraintSet s;
  // x != 5
  Constraint c{Ne, {Literal(int32_t(5))}};
  s.set(c);

  // Checks out versus itself.
  EXPECT_EQ(s.proves(c), True);

  // x == 10: we don't know.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(10))}}), Unknown);

  // x != 15: we don't know.
  EXPECT_EQ(s.proves(Constraint{Ne, {Literal(int32_t(15))}}), Unknown);

  // x == 5: we can infer false.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(5))}}), False);
}

TEST(ConstraintTest, TestMulti) {
  AndedConstraintSet s;
  // x != 5 && x != 10
  Constraint c{Ne, {Literal(int32_t(5))}};
  Constraint d{Ne, {Literal(int32_t(10))}};
  s.set(c);
  s.approximateAnd(d);

  // Each checks out versus itself.
  EXPECT_EQ(s.proves(c), True);
  EXPECT_EQ(s.proves(d), True);

  // x == 5: false.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(5))}}), False);

  // x == 10: false.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(10))}}), False);

  // x == 15: we don't know.
  EXPECT_EQ(s.proves(Constraint{Eq, {Literal(int32_t(15))}}), Unknown);

  // x != 15: we don't know.
  EXPECT_EQ(s.proves(Constraint{Ne, {Literal(int32_t(15))}}), Unknown);
}

TEST(ConstraintTest, TestSets) {
  // x == 5
  Constraint c{Eq, {Literal(int32_t(5))}};

  AndedConstraintSet s;

  // Any set always proves itself to be true.
  EXPECT_EQ(s.proves(s), True);

  // Ditto after adding something.
  s.set(c);
  EXPECT_EQ(s.proves(s), True);

  // Another set, empty.
  AndedConstraintSet t;

  // Make both sets contain the same stuff.
  t.set(c);
  EXPECT_EQ(s.proves(t), True);

  // Now t has *different* stuff, x == 10, which given s is false.
  t.set(Constraint{Eq, {Literal(int32_t(10))}});
  EXPECT_EQ(s.proves(t), False);

  // Same, with x != 10. Now we know it is true.
  t.set(Constraint{Ne, {Literal(int32_t(10))}});
  EXPECT_EQ(s.proves(t), True);

  // In reverse, we can infer nothing: knowing x != 10 does not say if x == 5.
  EXPECT_EQ(t.proves(s), Unknown);
}

TEST(ConstraintTest, TestSetsUnknown) {
  // x != 5
  // x != 10
  AndedConstraintSet s;
  s.set(Constraint{Ne, {Literal(int32_t(5))}});
  s.approximateAnd(Constraint{Ne, {Literal(int32_t(10))}});

  // x != 20, which is unknown by s.
  AndedConstraintSet t;
  t.set(Constraint{Ne, {Literal(int32_t(20))}});
  EXPECT_EQ(s.proves(t), Unknown);

  // Add x == 10, which is false by s, and so the whole thing is false.
  t.set(Constraint{Eq, {Literal(int32_t(10))}});
  EXPECT_EQ(s.proves(t), False);
}

TEST(ConstraintTest, TestOrTrivial) {
  // { x == 5 }
  AndedConstraintSet s;
  s.set(Constraint{Eq, {Literal(int32_t(5))}});

  // { }
  AndedConstraintSet empty;
  empty.setProvesNothing();

  // Anything ORed with the empty set becomes the empty set: if one side can
  // prove nothing, neither can the result.
  auto t = s;
  t.approximateOr(empty);
  EXPECT_EQ(t, empty);

  // Flipped.
  t = empty;
  t.approximateOr(s);
  EXPECT_EQ(t, empty);

  // ORing with oneself changes nothing
  t = s;
  t.approximateOr(s);
  EXPECT_EQ(t, s);
}

TEST(ConstraintTest, TestOrImplies) {
  // { x == 5 }
  AndedConstraintSet s;
  s.set(Constraint{Eq, {Literal(int32_t(5))}});

  // { x != 10 }
  AndedConstraintSet t;
  t.set(Constraint{Ne, {Literal(int32_t(10))}});

  // ORing these leaves us with x != 10.
  auto u = s;
  u.approximateOr(t);
  EXPECT_EQ(u, t);

  // Flipped.
  u = t;
  u.approximateOr(s);
  EXPECT_EQ(u, t);
}

TEST(ConstraintTest, TestMaxCapacity) {
  EXPECT_EQ(MaxConstraints, 3);

  // Max out with x != 10, 20, 30
  Constraint not10{Ne, {Literal(int32_t(10))}};
  Constraint not20{Ne, {Literal(int32_t(20))}};
  Constraint not30{Ne, {Literal(int32_t(30))}};

  AndedConstraintSet s;
  s.set(not10);
  s.approximateAnd(not20);
  s.approximateAnd(not30);

  // We can prove all those.
  EXPECT_EQ(s.proves(not10), True);
  EXPECT_EQ(s.proves(not20), True);
  EXPECT_EQ(s.proves(not30), True);

  // Add another, exceeding the capacity.
  Constraint not40{Ne, {Literal(int32_t(40))}};
  s.approximateAnd(not40);

  // We can prove the old ones but not the new.
  EXPECT_EQ(s.proves(not10), True);
  EXPECT_EQ(s.proves(not20), True);
  EXPECT_EQ(s.proves(not30), True);
  EXPECT_EQ(s.proves(not40), Unknown);
}

TEST(ConstraintTest, TestDeduplication) {
  Constraint eq10{Eq, {Literal(int32_t(10))}};

  AndedConstraintSet s;
  EXPECT_EQ(s.size(), 0);
  s.set(eq10);
  EXPECT_EQ(s.size(), 1);
  // The size does not increase when we add eq10 again.
  s.approximateAnd(eq10);
  EXPECT_EQ(s.size(), 1);
}

TEST(ConstraintTest, TestDeredundancy) {
  Constraint eq0{Eq, {Literal(int32_t(0))}};
  Constraint ne1{Ne, {Literal(int32_t(1))}};

  // If x == 0, then x != 1 is redundant, and does not need to be added, is it
  // is implied by x == 0.
  AndedConstraintSet s;
  s.set(eq0);
  s.approximateAnd(ne1);
  EXPECT_EQ(s.size(), 1);
  EXPECT_EQ(s[0], eq0);

  // Reverse order, same result, even though we added x == 0 last: we remove
  // x != 1.
  AndedConstraintSet t;
  t.set(ne1);
  t.approximateAnd(eq0);
  EXPECT_EQ(t.size(), 1);
  EXPECT_EQ(t[0], eq0);
}

static void checkOr(const AndedConstraintSet& a,
                    const AndedConstraintSet& b,
                    const AndedConstraintSet& result) {
  auto ored = a;
  ored.approximateOr(b);
  EXPECT_EQ(ored, result);

  ored = b;
  ored.approximateOr(a);
  EXPECT_EQ(ored, result);
}

TEST(ConstraintTest, TestOrInequality) {
  // x == 5 || x >= 0  =>  x >= 0
  AndedConstraintSet eq5{{Eq, {Literal(int32_t(5))}}};
  AndedConstraintSet ge0{{GeU, {Literal(int32_t(0))}}};
  checkOr(eq5, ge0, ge0);

  // x == 5 || x > 5  =>  x >= 5
  AndedConstraintSet gts5{{GtS, {Literal(int32_t(5))}}};
  AndedConstraintSet ges5{{GeS, {Literal(int32_t(5))}}};
  checkOr(eq5, gts5, ges5);

  // x == 5 || x >= 5  =>  x >= 5
  checkOr(eq5, ges5, ges5);

  // x == 5 || x >= 6  =>  x >= 5
  AndedConstraintSet ges6{{GeS, {Literal(int32_t(6))}}};
  checkOr(eq5, ges6, ges5);

  // TODO: x == 5 || x >= 7  =>  x >= 5  TODO
  AndedConstraintSet ges7{{GeS, {Literal(int32_t(7))}}};
  auto empty = AndedConstraintSet::makeProvesNothing();
  checkOr(eq5, ges7, empty);

  // x > 5 || x >= 6  =>  x > 5
  checkOr(gts5, ges6, gts5);

  // x > 5 || x >= 5  =>  x >= 5
  checkOr(gts5, ges5, ges5);

  // Careful of overflow:
  // x == signed_max || x >= (signed_max + 1 === signed_min) != x >= signed_max
  AndedConstraintSet eqMax{
    {Eq, {Literal(std::numeric_limits<int32_t>::max())}}};
  AndedConstraintSet gesMin{
    {GeS, {Literal(std::numeric_limits<int32_t>::min())}}};
  // TODO: x >= signed_min is always true, so this could be empty
  checkOr(eqMax, gesMin, gesMin);

  // Careful of overflow:
  // x > signed_max || x >= (signed_max + 1 === signed_min) != x > signed_max
  AndedConstraintSet gtsMax{
    {GtS, {Literal(std::numeric_limits<int32_t>::max())}}};
  // TODO: x > signed_max is always false, so this could return a contradiction
  checkOr(gtsMax, gesMin, empty);
}

TEST(ConstraintTest, TestOrLoop) {
  // Check common loop patterns at the loop top (merging an initial value with
  // an incremented and bounded one):
  // { x == A } || { x > A && x <= B }   ==>   { x >= A && x <= B }

  // { x == 5 } || { x > 5 && x <= 42 }   ==>   { x >= 5 && x <= 42 }
  AndedConstraintSet left{{Eq, {Literal(int32_t(5))}}};
  AndedConstraintSet right(
    {{GtS, {Literal(int32_t(5))}}, {LeS, {Literal(int32_t(42))}}});
  AndedConstraintSet result(
    {{GeS, {Literal(int32_t(5))}}, {LeS, {Literal(int32_t(42))}}});
  checkOr(left, right, result);

  // Changes to constants:

  // Change 5 on the left to 7:
  // { x == 7 } || { x > 5 && x <= 42 }   ==>   { x > 5 && x <= 42}
  AndedConstraintSet left7{{Eq, {Literal(int32_t(7))}}};
  checkOr(left7, right, right);

  // Change 5 on the left to 99:
  // { x == 99 } || { x > 5 && x <= 42 }   ==>   { x > 5 }
  // TODO: we could emit a range (5, 99]
  AndedConstraintSet left99{{Eq, {Literal(int32_t(99))}}};
  AndedConstraintSet rightOnly5{{GtS, {Literal(int32_t(5))}}};
  checkOr(left99, right, rightOnly5);

  // Change 5 on the left to 4:
  // { x == 4 } || { x > 5 && x <= 42 }   ==>   { x <= 42 }
  // TODO: we could emit a range [4, 42]
  AndedConstraintSet left4{{Eq, {Literal(int32_t(4))}}};
  AndedConstraintSet rightOnly42({{LeS, {Literal(int32_t(42))}}});
  checkOr(left4, right, rightOnly42);

  // Change 5 on the right to 6:
  // { x == 5 } || { x > 6 && x <= 42 }   ==>   { x <= 42 }
  AndedConstraintSet right6(
    {{GtS, {Literal(int32_t(6))}}, {LeS, {Literal(int32_t(42))}}});
  checkOr(left, right6, rightOnly42);

  // Changes to operations:

  // Change the Eq on the left to Ne. We fail to find anything for the OR.
  // { x != 5 } || { x > 5 && x <= 42 }   ==>   {}
  // TODO: we could emit x != 5
  AndedConstraintSet leftNe{{Ne, {Literal(int32_t(5))}}};
  auto empty = AndedConstraintSet::makeProvesNothing();
  checkOr(leftNe, right, empty);

  // Change the GtS on the right to GtU:
  // { x == 5 } || { x >U 5 && x <= 42 }   ==>   { x >=U 5 && x <= 42 }
  AndedConstraintSet rightGtU(
    {{GtU, {Literal(int32_t(5))}}, {LeS, {Literal(int32_t(42))}}});
  AndedConstraintSet resultMixed(
    {{GeU, {Literal(int32_t(5))}}, {LeS, {Literal(int32_t(42))}}});
  checkOr(left, rightGtU, resultMixed);

  // Change the LeS on the right to LeU:
  // { x == 5 } || { x > 5 && x <=U 42 }   ==>   { x >= 5 && x <=U 42 }
  AndedConstraintSet rightLeU(
    {{GtS, {Literal(int32_t(5))}}, {LeU, {Literal(int32_t(42))}}});
  AndedConstraintSet rightGesLeU(
    {{GeS, {Literal(int32_t(5))}}, {LeU, {Literal(int32_t(42))}}});
  checkOr(left, rightLeU, rightGesLeU);

  // Add an operation on the right, x != 21:
  // { x == 5 } || { x >  5 && x <= 42 && x != 21 }   ==>
  //               { x >= 5 && x <= 42 && x != 21 }
  AndedConstraintSet rightAdded({{GtS, {Literal(int32_t(5))}},
                                 {LeS, {Literal(int32_t(42))}},
                                 {Ne, {Literal(int32_t(21))}}});
  AndedConstraintSet resultAdded({{GeS, {Literal(int32_t(5))}},
                                  {LeS, {Literal(int32_t(42))}},
                                  {Ne, {Literal(int32_t(21))}}});
  checkOr(left, rightAdded, resultAdded);
}

TEST(ConstraintTest, TestOrLoopUnsigned) {
  // As above, but unsigned.

  // { x == 5 } || { x > 5 && x <= 42 }   ==>   { x >= 5 && x <= 42 }
  AndedConstraintSet left{{Eq, {Literal(int32_t(5))}}};
  AndedConstraintSet right(
    {{GtU, {Literal(int32_t(5))}}, {LeU, {Literal(int32_t(42))}}});
  AndedConstraintSet result(
    {{GeU, {Literal(int32_t(5))}}, {LeU, {Literal(int32_t(42))}}});
  checkOr(left, right, result);

  // Changes to constants:

  // Change 5 on the left to 7:
  // { x == 7 } || { x > 5 && x <= 42 }   ==>   { x > 5 && x <= 42}
  AndedConstraintSet left7{{Eq, {Literal(int32_t(7))}}};
  checkOr(left7, right, right);

  // Change 5 on the left to 99:
  // { x == 99 } || { x > 5 && x <= 42 }   ==>   { x > 5 }
  // TODO: we could emit a range (5, 99]
  AndedConstraintSet left99{{Eq, {Literal(int32_t(99))}}};
  AndedConstraintSet rightOnly5{{GtU, {Literal(int32_t(5))}}};
  checkOr(left99, right, rightOnly5);

  // Change 5 on the left to 4:
  // { x == 4 } || { x > 5 && x <= 42 }   ==>   { x <= 42 }
  // TODO: we could emit a range [4, 42]
  AndedConstraintSet left4{{Eq, {Literal(int32_t(4))}}};
  AndedConstraintSet rightOnly42({{LeU, {Literal(int32_t(42))}}});
  checkOr(left4, right, rightOnly42);

  // Change 5 on the right to 6:
  // { x == 5 } || { x > 6 && x <= 42 }   ==>   { x <= 42 }
  AndedConstraintSet right6(
    {{GtU, {Literal(int32_t(6))}}, {LeU, {Literal(int32_t(42))}}});
  checkOr(left, right6, rightOnly42);

  // Changes to operations:

  // Change the Eq on the left to Ne. We fail to find anything for the OR.
  // { x != 5 } || { x > 5 && x <= 42 }   ==>   {}
  // TODO: we could emit x != 5
  AndedConstraintSet leftNe{{Ne, {Literal(int32_t(5))}}};
  auto empty = AndedConstraintSet::makeProvesNothing();
  checkOr(leftNe, right, empty);

  // Add an operation on the right, x != 21:
  // { x == 5 } || { x >  5 && x <= 42 && x != 21 }   ==>
  //               { x >= 5 && x <= 42 && x != 21 }
  AndedConstraintSet rightAdded({{GtU, {Literal(int32_t(5))}},
                                 {LeU, {Literal(int32_t(42))}},
                                 {Ne, {Literal(int32_t(21))}}});
  AndedConstraintSet resultAdded({{GeU, {Literal(int32_t(5))}},
                                  {LeU, {Literal(int32_t(42))}},
                                  {Ne, {Literal(int32_t(21))}}});
  checkOr(left, rightAdded, resultAdded);
}

static void checkAnd(const AndedConstraintSet& a,
                     const AndedConstraintSet& b,
                     const AndedConstraintSet& result) {
  auto anded = a;
  for (auto& bc : b) {
    anded.approximateAnd(bc);
  }
  EXPECT_EQ(anded, result);

  anded = b;
  for (auto& ac : a) {
    anded.approximateAnd(ac);
  }
  EXPECT_EQ(anded, result);
}

TEST(ConstraintTest, TestAndInequality) {
  // x == 5 && x >= 0  =>  x == 5
  AndedConstraintSet eq5{{Eq, {Literal(int32_t(5))}}};
  AndedConstraintSet ge0{{GeS, {Literal(int32_t(0))}}};
  checkAnd(eq5, ge0, eq5);

  // x == 5 && x >= 5  =>  x == 5
  AndedConstraintSet ge5{{GeS, {Literal(int32_t(5))}}};
  checkAnd(eq5, ge5, eq5);

  // x == 5 && x >= 6  =>  contradiction
  AndedConstraintSet ge6{{GeS, {Literal(int32_t(6))}}};
  AndedConstraintSet contradiction;
  checkAnd(eq5, ge6, contradiction);
}

TEST(ConstraintTest, TestAndLoop) {
  // Check common loop patterns after incrementing and bounds-checking:
  // x <= A && x < A  =>  x < A

  // x <= 5 && x < 5  =>  x < 5
  AndedConstraintSet le5{{LeS, {Literal(int32_t(5))}}};
  AndedConstraintSet lt5{{LtS, {Literal(int32_t(5))}}};
  checkAnd(le5, lt5, lt5);

  // Ditto, but unsigned.
  AndedConstraintSet le5U{{LeU, {Literal(int32_t(5))}}};
  AndedConstraintSet lt5U{{LtU, {Literal(int32_t(5))}}};
  checkAnd(le5U, lt5U, lt5U);

  // Mixing signed and unsigned does not optimize (so we just end up ANDing both
  // inputs).
  checkAnd(le5, lt5U, AndedConstraintSet{le5[0], lt5U[0]});

  // Different constants do not optimize, but could TODO
  AndedConstraintSet lt6{{LtS, {Literal(int32_t(6))}}};
  checkAnd(le5, lt6, AndedConstraintSet{le5[0], lt6[0]});

  // A non-constant.
  // x <= y && x < y  =>  x < y
  AndedConstraintSet ley{{LeS, {Index(1)}}};
  AndedConstraintSet lty{{LtS, {Index(1)}}};
  checkAnd(ley, lty, lty);

  // A non-constant with extra info.
  // { x <= y && x != 42 } && x < y  =>  x < y && x != 42
  Constraint ne42{Ne, {Literal(int32_t(42))}};
  checkAnd({ley[0], ne42}, lty, {lty[0], ne42});

  // Extra info on the other side, same result.
  // x <= y && { x < y && x != 42 }  =>  x < y && x != 42
  checkAnd(ley, {lty[0], ne42}, {lty[0], ne42});
}

TEST(ConstraintTest, TestBasicBlockConstraintMap) {
  // Maps begin unreachable.
  BasicBlockConstraintMap map;

  EXPECT_TRUE(map.unreachable);
  map.setReachable();
  EXPECT_FALSE(map.unreachable);
}

// Check that a set is equal to a constraint.
static void check(const AndedConstraintSet& s, const Constraint& c) {
  EXPECT_EQ(s.size(), 1);
  EXPECT_EQ(s[0], c);
}

TEST(ConstraintTest, TestBasicBlockConstraintMap_Set) {
  Constraint eq0{Eq, {Literal(int32_t(0))}};
  Constraint eq1{Eq, {Literal(int32_t(1))}};
  Constraint eq2{Eq, {Literal(int32_t(2))}};

  BasicBlockConstraintMap map;
  map.setReachable();

  // Set local 0 to 0. It should read back the same.
  map.set(0, eq0);
  check(map.get(0), eq0);

  // Set another value, replacing the first.
  map.set(0, eq1);
  check(map.get(0), eq1);

  // Set a value using an expression.
  Const c;
  c.value = Literal(int32_t(2));
  c.type = Type::i32;
  map.set(0, &c);
  check(map.get(0), eq2);

  // Set an unfamiliar expression, leading to us knowing nothing.
  Nop nop;
  map.set(0, &nop);
  EXPECT_TRUE(map.get(0).provesNothing());
}

TEST(ConstraintTest, TestIncrement) {
  BasicBlockConstraintMap map;
  map.setReachable();

  // Set up an increment operation, an add which does $0 + 1
  LocalGet get;
  get.index = 0;
  get.type = Type::i32;

  Const c;
  c.value = Literal(int32_t(1));
  c.type = Type::i32;

  Binary add;
  add.op = AddInt32;
  add.type = Type::i32;
  add.left = &get;
  add.right = &c;

  // $0 = 0, $1 = $0 + 1, so $1 = 1 (and $0 is unchanged).
  map.set(0, {Eq, {Literal(int32_t(0))}});
  map.set(1, &add);
  check(map.get(0), {Eq, {Literal(int32_t(0))}});
  check(map.get(1), {Eq, {Literal(int32_t(1))}});

  // $0 = $0 + 1, where $0 was 0, so it is now 1.
  map.set(0, &add);
  check(map.get(0), {Eq, {Literal(int32_t(1))}});

  // $0 >= 5, $0++  =>  $0 > 5 (signed)
  map.set(0, {GeS, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {GtS, {Literal(int32_t(5))}});

  // Ditto, unsigned
  map.set(0, {GeU, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {GtU, {Literal(int32_t(5))}});

  // $0 < 5, $0++  =>  $0 <= 5 (signed)
  map.set(0, {LtS, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {LeS, {Literal(int32_t(5))}});

  // Ditto, unsigned
  map.set(0, {LtU, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {LeU, {Literal(int32_t(5))}});

  // $0 <= 5, $0++  =>  $0 <= 6 (signed)
  map.set(0, {LeS, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {LeS, {Literal(int32_t(6))}});

  // Ditto, unsigned
  map.set(0, {LeU, {Literal(int32_t(5))}});
  map.set(0, &add);
  check(map.get(0), {LeU, {Literal(int32_t(6))}});

  // $0 <= max_signed, $0++  =>  nothing, because it would overflow
  map.set(0, {LeS, {Literal::makeSignedMax(Type::i32)}});
  map.set(0, &add);
  EXPECT_TRUE(map.get(0).provesNothing());

  // $0 <= max_unsigned, $0++  =>  nothing, because it would overflow
  map.set(0, {LeU, {Literal::makeUnsignedMax(Type::i32)}});
  map.set(0, &add);
  EXPECT_TRUE(map.get(0).provesNothing());

  // However, an unsigned operation on the signed max is fine.
  map.set(0, {LeU, {Literal::makeSignedMax(Type::i32)}});
  map.set(0, &add);
  auto one = Literal::makeFromInt32(1, Type::i32);
  check(map.get(0), {LeU, {Literal::makeSignedMax(Type::i32).add(one)}});

  // Multiple constraints at once:
  // $0 >= 10 && $0 < 20, $0++  =>  $0 > 10 && $0 <= 20
  map.set(0, {GeS, {Literal(int32_t(10))}});
  map.approximateAnd(0, {LtS, {Literal(int32_t(20))}});
  map.set(0, &add);
  EXPECT_EQ(map.get(0),
            (AndedConstraintSet{{GtS, {Literal(int32_t(10))}},
                                {LeS, {Literal(int32_t(20))}}}));

  // $0 >= 10 && $0 <= max_signed, $0++  =>  $0 > 10 (overflowing constraint
  // removed)
  map.set(0, {GeS, {Literal(int32_t(10))}});
  map.approximateAnd(0, {LeS, {Literal::makeSignedMax(Type::i32)}});
  map.set(0, &add);
  EXPECT_EQ(map.get(0), (AndedConstraintSet{{GtS, {Literal(int32_t(10))}}}));

  // $0 >= 10 && $0 == $2, $0++  =>  $0 > 10 (non-constant term removed)
  map.set(0, {GeS, {Literal(int32_t(10))}});
  map.approximateAnd(0, {Eq, {Index(2)}});
  map.set(0, &add);
  EXPECT_EQ(map.get(0), (AndedConstraintSet{{GtS, {Literal(int32_t(10))}}}));
}

TEST(ConstraintTest, TestEqConstraints) {
  BasicBlockConstraintMap map;
  map.setReachable();

  // $0 == 42
  map.set(0, {Eq, {Literal(int32_t(42))}});

  // $0 < $1
  map.approximateAnd(0, {LtS, {Index(int32_t(1))}});

  // $1 has $1 > 42: we constant-propagated the value of $0. This is better than
  // having $1 > $0 and needing to look $0 up.
  check(map.get(1), {GtS, {Literal(int32_t(42))}});
}