int128: optimize and add test cases

For add, the carry only requires checking one of the arguments.
For sub and neg, we can similarly optimize computation of the
carry.

For ge, we can just do lexicographic order.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 212 insertions, 0 deletions

diff --git a/tests/test-int128.c b/tests/test-int128.c
new file mode 100644
index 0000000..5aca032
--- /dev/null
+++ b/tests/test-int128.c
@@ -0,0 +1,212 @@
+/*
+ * Test Int128 arithmetic
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include <glib.h>
+#include <stdio.h>
+#include "qemu/int128.h"
+#include "qemu/osdep.h"
+
+static uint32_t tests[8] = {
+    0x00000000, 0x00000001, 0x7FFFFFFE, 0x7FFFFFFF,
+    0x80000000, 0x80000001, 0xFFFFFFFE, 0xFFFFFFFF,
+};
+
+#define LOW    3ULL
+#define HIGH   (1ULL << 63)
+#define MIDDLE (-1ULL & ~LOW & ~HIGH)
+
+static uint64_t expand16(unsigned x)
+{
+    return (x & LOW) | ((x & 4) ? MIDDLE : 0) | (x & 0x8000 ? HIGH : 0);
+}
+
+static Int128 expand(uint32_t x)
+{
+    uint64_t l, h;
+    l = expand16(x & 65535);
+    h = expand16(x >> 16);
+    return (Int128) {l, h};
+};
+
+static void test_and(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            Int128 a = expand(tests[i]);
+            Int128 b = expand(tests[j]);
+            Int128 r = expand(tests[i] & tests[j]);
+            Int128 s = int128_and(a, b);
+            g_assert_cmpuint(r.lo, ==, s.lo);
+            g_assert_cmpuint(r.hi, ==, s.hi);
+        }
+    }
+}
+
+static void test_add(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            Int128 a = expand(tests[i]);
+            Int128 b = expand(tests[j]);
+            Int128 r = expand(tests[i] + tests[j]);
+            Int128 s = int128_add(a, b);
+            g_assert_cmpuint(r.lo, ==, s.lo);
+            g_assert_cmpuint(r.hi, ==, s.hi);
+        }
+    }
+}
+
+static void test_sub(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            Int128 a = expand(tests[i]);
+            Int128 b = expand(tests[j]);
+            Int128 r = expand(tests[i] - tests[j]);
+            Int128 s = int128_sub(a, b);
+            g_assert_cmpuint(r.lo, ==, s.lo);
+            g_assert_cmpuint(r.hi, ==, s.hi);
+        }
+    }
+}
+
+static void test_neg(void)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        Int128 a = expand(tests[i]);
+        Int128 r = expand(-tests[i]);
+        Int128 s = int128_neg(a);
+        g_assert_cmpuint(r.lo, ==, s.lo);
+        g_assert_cmpuint(r.hi, ==, s.hi);
+    }
+}
+
+static void test_nz(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            Int128 a = expand(tests[i]);
+            g_assert_cmpuint(int128_nz(a), ==, tests[i] != 0);
+        }
+    }
+}
+
+static void test_le(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            /* Signed comparison */
+            int32_t a = (int32_t) tests[i];
+            int32_t b = (int32_t) tests[j];
+            g_assert_cmpuint(int128_le(expand(a), expand(b)), ==, a <= b);
+        }
+    }
+}
+
+static void test_lt(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            /* Signed comparison */
+            int32_t a = (int32_t) tests[i];
+            int32_t b = (int32_t) tests[j];
+            g_assert_cmpuint(int128_lt(expand(a), expand(b)), ==, a < b);
+        }
+    }
+}
+
+static void test_ge(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            /* Signed comparison */
+            int32_t a = (int32_t) tests[i];
+            int32_t b = (int32_t) tests[j];
+            g_assert_cmpuint(int128_ge(expand(a), expand(b)), ==, a >= b);
+        }
+    }
+}
+
+static void test_gt(void)
+{
+    int i, j;
+
+    for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+        for (j = 0; j < ARRAY_SIZE(tests); ++j) {
+            /* Signed comparison */
+            int32_t a = (int32_t) tests[i];
+            int32_t b = (int32_t) tests[j];
+            g_assert_cmpuint(int128_gt(expand(a), expand(b)), ==, a > b);
+        }
+    }
+}
+
+/* Make sure to test undefined behavior at runtime! */
+
+static void __attribute__((__noinline__, __noclone__))
+test_rshift_one(uint32_t x, int n, uint64_t h, uint64_t l)
+{
+    Int128 a = expand(x);
+    Int128 r = int128_rshift(a, n);
+    g_assert_cmpuint(r.lo, ==, l);
+    g_assert_cmpuint(r.hi, ==, h);
+}
+
+static void test_rshift(void)
+{
+    test_rshift_one(0x00010000U, 64, 0x0000000000000000ULL, 0x0000000000000001ULL);
+    test_rshift_one(0x80010000U, 64, 0xFFFFFFFFFFFFFFFFULL, 0x8000000000000001ULL);
+    test_rshift_one(0x7FFE0000U, 64, 0x0000000000000000ULL, 0x7FFFFFFFFFFFFFFEULL);
+    test_rshift_one(0xFFFE0000U, 64, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFEULL);
+    test_rshift_one(0x00010000U, 60, 0x0000000000000000ULL, 0x0000000000000010ULL);
+    test_rshift_one(0x80010000U, 60, 0xFFFFFFFFFFFFFFF8ULL, 0x0000000000000010ULL);
+    test_rshift_one(0x00018000U, 60, 0x0000000000000000ULL, 0x0000000000000018ULL);
+    test_rshift_one(0x80018000U, 60, 0xFFFFFFFFFFFFFFF8ULL, 0x0000000000000018ULL);
+    test_rshift_one(0x7FFE0000U, 60, 0x0000000000000007ULL, 0xFFFFFFFFFFFFFFE0ULL);
+    test_rshift_one(0xFFFE0000U, 60, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFE0ULL);
+    test_rshift_one(0x7FFE8000U, 60, 0x0000000000000007ULL, 0xFFFFFFFFFFFFFFE8ULL);
+    test_rshift_one(0xFFFE8000U, 60, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFE8ULL);
+    test_rshift_one(0x00018000U,  0, 0x0000000000000001ULL, 0x8000000000000000ULL);
+    test_rshift_one(0x80018000U,  0, 0x8000000000000001ULL, 0x8000000000000000ULL);
+    test_rshift_one(0x7FFE0000U,  0, 0x7FFFFFFFFFFFFFFEULL, 0x0000000000000000ULL);
+    test_rshift_one(0xFFFE0000U,  0, 0xFFFFFFFFFFFFFFFEULL, 0x0000000000000000ULL);
+    test_rshift_one(0x7FFE8000U,  0, 0x7FFFFFFFFFFFFFFEULL, 0x8000000000000000ULL);
+    test_rshift_one(0xFFFE8000U,  0, 0xFFFFFFFFFFFFFFFEULL, 0x8000000000000000ULL);
+}
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+    g_test_add_func("/int128/int128_and", test_and);
+    g_test_add_func("/int128/int128_add", test_add);
+    g_test_add_func("/int128/int128_sub", test_sub);
+    g_test_add_func("/int128/int128_neg", test_neg);
+    g_test_add_func("/int128/int128_nz", test_nz);
+    g_test_add_func("/int128/int128_le", test_le);
+    g_test_add_func("/int128/int128_lt", test_lt);
+    g_test_add_func("/int128/int128_ge", test_ge);
+    g_test_add_func("/int128/int128_gt", test_gt);
+    g_test_add_func("/int128/int128_rshift", test_rshift);
+    return g_test_run();
+}