Add the div module, which allows fast division by dynamic values.

test/unit/div.c

@@ -0,0 +1,29 @@
+#include "test/jemalloc_test.h"
+
+#include "jemalloc/internal/div.h"
+
+TEST_BEGIN(test_div_exhaustive) {
+	for (size_t divisor = 2; divisor < 1000 * 1000; ++divisor) {
+		div_info_t div_info;
+		div_init(&div_info, divisor);
+		size_t max = 1000 * divisor;
+		if (max < 1000 * 1000) {
+			max = 1000 * 1000;
+		}
+		for (size_t dividend = 0; dividend < 1000 * divisor;
+		    dividend += divisor) {
+			size_t quotient = div_compute(
+			    &div_info, dividend);
+			assert_zu_eq(dividend, quotient * divisor,
+			    "With divisor = %zu, dividend = %zu, "
+			    "got quotient %zu", divisor, dividend, quotient);
+		}
+	}
+}
+TEST_END
+
+int
+main(void) {
+	return test_no_reentrancy(
+	    test_div_exhaustive);
+}