[unittests] Add a few tests for computeKnownBits with ranges

[qcolombet]

Summary

These tests make sure that the range information is properly
understood during computeKnownBits analysis.

NFC

[RKSimon]

LGTM with minor query

llvm/unittests/Analysis/ValueTrackingTest.cpp

1134

Is it worth adding Known.getMinValue()/getMaxValue() checks as well?

1157

Is it worth adding Known.getMinValue()/getMaxValue() checks as well?

[qcolombet]

• Add getMinValue/getMaxValue

llvm/unittests/Analysis/ValueTrackingTest.cpp

parseAssembly("define void @test() {\n"
                 "declare i32 @any_num()\n");
   AssumptionCache AC(*F);
   KnownBits Known = computeKnownBits(A, M->getDataLayout(), /* Depth */ 0, &AC,
                                      F->front().getTerminator());
   EXPECT_EQ(Known.Zero.getZExtValue(), 31u);
   EXPECT_EQ(Known.One.getZExtValue(), 0u);
 }
 
+TEST_F(ComputeKnownBitsTest, ComputeKnownBitsAddWithRange) {
+  parseAssembly("define void @test(i64* %p) {\n"
+                "  %A = load i64, i64* %p, !range !{i64 64, i64 65536}\n"
+                "  %APlus512 = add i64 %A, 512\n"
+                "  %c = icmp ugt i64 %APlus512, 523\n"
+                "  call void @llvm.assume(i1 %c)\n"
+                "  ret void\n"
+                "}\n"
+                "declare void @llvm.assume(i1)\n");
+  AssumptionCache AC(*F);
+  KnownBits Known = computeKnownBits(A, M->getDataLayout(), /* Depth */ 0, &AC,
+                                     F->front().getTerminator());
+  EXPECT_EQ(Known.Zero.getZExtValue(), ~(65536llu - 1));
+  EXPECT_EQ(Known.One.getZExtValue(), 0u);
+  Instruction &APlus512 = findInstructionByName(F, "APlus512");
+  Known = computeKnownBits(&APlus512, M->getDataLayout(), /* Depth */ 0, &AC,
+                           F->front().getTerminator());
+  // We know of one less zero because 512 may have produced a 1 that
+  // got carried all the way to the first trailing zero.
+  EXPECT_EQ(Known.Zero.getZExtValue(), (~(65536llu - 1)) << 1);
+  EXPECT_EQ(Known.One.getZExtValue(), 0u);
+  // The known range is not precise given computeKnownBits works
+  // with the masks of zeros and ones, not the ranges.
+  EXPECT_EQ(Known.getMinValue(), 0u);
+  EXPECT_EQ(Known.getMaxValue(), 131071);
+}
+
+// 512 + [32, 64) doesn't produce overlapping bits.
+// Make sure we get all the individual bits properly.
+TEST_F(ComputeKnownBitsTest, ComputeKnownBitsAddWithRangeNoOverlap) {
+  parseAssembly("define void @test(i64* %p) {\n"
+                "  %A = load i64, i64* %p, !range !{i64 32, i64 64}\n"
+                "  %APlus512 = add i64 %A, 512\n"
+                "  %c = icmp ugt i64 %APlus512, 523\n"
+                "  call void @llvm.assume(i1 %c)\n"
+                "  ret void\n"
+                "}\n"
+                "declare void @llvm.assume(i1)\n");
+  AssumptionCache AC(*F);
+  KnownBits Known = computeKnownBits(A, M->getDataLayout(), /* Depth */ 0, &AC,
+                                     F->front().getTerminator());
+  EXPECT_EQ(Known.Zero.getZExtValue(), ~(64llu - 1));
+  EXPECT_EQ(Known.One.getZExtValue(), 32u);
+  Instruction &APlus512 = findInstructionByName(F, "APlus512");
+  Known = computeKnownBits(&APlus512, M->getDataLayout(), /* Depth */ 0, &AC,
+                           F->front().getTerminator());
+  EXPECT_EQ(Known.Zero.getZExtValue(), ~512llu & ~(64llu - 1));
+  EXPECT_EQ(Known.One.getZExtValue(), 512u | 32u);
+  // The known range is not precise given computeKnownBits works
+  // with the masks of zeros and ones, not the ranges.
+  EXPECT_EQ(Known.getMinValue(), 544);
+  EXPECT_EQ(Known.getMaxValue(), 575);
+}
+
 class IsBytewiseValueTest : public ValueTrackingTest,
                             public ::testing::WithParamInterface<
                                 std::pair<const char *, const char *>> {
 protected:
 };
 
 const std::pair<const char *, const char *> IsBytewiseValueTests[] = {
     {