[APInt] Fix tests that had wrong assumption about sdivs with negative quotient.

[timshen]

This fixes wrong tests introduced by D48498

[sanjoy]

Can you please describe what was wrong about the unit tests in the commit message?

llvm/unittests/ADT/APIntTest.cpp

2630

Can this be EXPECT_EQ?

[timshen]

EXPECT_TRUE -> EXPECT_EQ.

[sanjoy.google]

lgtm

llvm/unittests/ADT/APIntTest.cpp

for (int64_t Ai = -128; Ai <= 127; Ai++) {
 
     if (Ai != 0) {
       APInt Zero(8, 0);
       EXPECT_EQ(0, APIntOps::RoundingSDiv(Zero, A, APInt::Rounding::UP));
       EXPECT_EQ(0, APIntOps::RoundingSDiv(Zero, A, APInt::Rounding::DOWN));
       EXPECT_EQ(0, APIntOps::RoundingSDiv(Zero, A, APInt::Rounding::TOWARD_ZERO));
     }
 
-    for (uint64_t Bi = -128; Bi <= 127; Bi++) {
+    for (int64_t Bi = -128; Bi <= 127; Bi++) {
       if (Bi == 0)
         continue;
 
       APInt B(8, Bi);
+      APInt QuoTowardZero = A.sdiv(B);
       {
         APInt Quo = APIntOps::RoundingSDiv(A, B, APInt::Rounding::UP);
-        auto Prod = Quo.sext(16) * B.sext(16);
-        EXPECT_TRUE(Prod.uge(A));
-        if (Prod.ugt(A)) {
-          EXPECT_TRUE(((Quo - 1).sext(16) * B.sext(16)).ult(A));
+        if (A.srem(B).isNullValue()) {
+          EXPECT_EQ(QuoTowardZero, Quo);
+        } else if (A.isNegative() !=
+                   B.isNegative()) { // if the math quotient is negative.
+          EXPECT_EQ(QuoTowardZero, Quo);
+        } else {
+          EXPECT_EQ(QuoTowardZero + 1, Quo);
         }
       }
       {
         APInt Quo = APIntOps::RoundingSDiv(A, B, APInt::Rounding::DOWN);
-        auto Prod = Quo.sext(16) * B.sext(16);
-        EXPECT_TRUE(Prod.ule(A));
-        if (Prod.ult(A)) {
-          EXPECT_TRUE(((Quo + 1).sext(16) * B.sext(16)).ugt(A));
-        }
+        if (A.srem(B).isNullValue()) {
+          EXPECT_EQ(QuoTowardZero, Quo);
+        } else if (A.isNegative() !=
+                   B.isNegative()) { // if the math quotient is negative.
+          EXPECT_EQ(QuoTowardZero - 1, Quo);
+        } else {
+          EXPECT_EQ(QuoTowardZero, Quo);
         }
-      {
-        APInt Quo = A.sdiv(B);
-        EXPECT_EQ(Quo, APIntOps::RoundingSDiv(A, B, APInt::Rounding::TOWARD_ZERO));
       }
+      EXPECT_EQ(QuoTowardZero,
+                APIntOps::RoundingSDiv(A, B, APInt::Rounding::TOWARD_ZERO));
     }
   }
 }
 
 TEST(APIntTest, umul_ov) {
   const std::pair<uint64_t, uint64_t> Overflows[] = {
       {0x8000000000000000, 2},
       {0x5555555555555556, 3},