1 files changed, 59 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/test/float_test.go b/src/cmd/compile/internal/test/float_test.go
index 7a5e27870f..00735e3cb1 100644
--- a/src/cmd/compile/internal/test/float_test.go
+++ b/src/cmd/compile/internal/test/float_test.go
@@ -727,6 +727,65 @@ func TestFusedNaNChecks32(t *testing.T) {
 	}
 }
 
+// minNormal64 is the smallest float64 value that is not subnormal.
+const minNormal64 = 2.2250738585072014e-308
+
+//go:noinline
+func isAbsLessThanMinNormal64(x float64) bool {
+	return math.Abs(x) < minNormal64
+}
+
+//go:noinline
+func isLessThanMinNormal64(x float64) bool {
+	return x < minNormal64
+}
+
+//go:noinline
+func isGreaterThanNegMinNormal64(x float64) bool {
+	return x > -minNormal64
+}
+
+//go:noinline
+func isGreaterThanOrEqualToMinNormal64(x float64) bool {
+	return math.Abs(x) >= minNormal64
+}
+
+func TestSubnormalComparisons(t *testing.T) {
+	tests := []struct {
+		value                  float64
+		isAbsLessThanMinNormal bool
+		isPositive             bool
+		isNegative             bool
+		isNaN                  bool
+	}{
+		{value: math.Inf(1), isPositive: true},
+		{value: math.MaxFloat64, isPositive: true},
+		{value: math.Inf(-1), isNegative: true},
+		{value: -math.MaxFloat64, isNegative: true},
+		{value: math.NaN(), isNaN: true},
+		{value: minNormal64, isPositive: true},
+		{value: minNormal64 / 2, isAbsLessThanMinNormal: true, isPositive: true},
+		{value: -minNormal64, isNegative: true},
+		{value: -minNormal64 / 2, isAbsLessThanMinNormal: true, isNegative: true},
+		{value: 0, isAbsLessThanMinNormal: true, isPositive: true},
+		{value: math.Copysign(0, -1), isAbsLessThanMinNormal: true, isNegative: true},
+	}
+
+	check := func(name string, f func(x float64) bool, value float64, want bool) {
+		got := f(value)
+		if got != want {
+			t.Errorf("%v(%g): want %v, got %v", name, value, want, got)
+		}
+	}
+
+	for _, test := range tests {
+		check("isAbsLessThanMinNormal64", isAbsLessThanMinNormal64, test.value, test.isAbsLessThanMinNormal)
+		check("isLessThanMinNormal64", isLessThanMinNormal64, test.value, test.isAbsLessThanMinNormal || test.isNegative)
+		check("isGreaterThanNegMinNormal64", isGreaterThanNegMinNormal64, test.value, test.isAbsLessThanMinNormal || test.isPositive)
+		check("isGreaterThanOrEqualToMinNormal64", isGreaterThanOrEqualToMinNormal64, test.value, !test.isAbsLessThanMinNormal && !test.isNaN)
+	}
+}
+
 var sinkFloat float64
 
 func BenchmarkMul2(b *testing.B) {