Add sub-and-branch-on-overflow tests

tests/bxsubr_u.c

@@ -0,0 +1,47 @@
+#include "test.h"
+
+static const intmax_t overflowed = 0xcabba9e5;
+
+static void
+run_test(jit_state_t *j, uint8_t *arena_base, size_t arena_size)
+{
+  jit_begin(j, arena_base, arena_size);
+
+  const jit_arg_abi_t abi[] = { JIT_ARG_ABI_INTMAX, JIT_ARG_ABI_INTMAX };
+  jit_arg_t args[2];
+  const jit_anyreg_t regs[] = { { .gpr=JIT_R0 }, { .gpr=JIT_R1 }};
+
+  jit_receive(j, 2, abi, args);
+  jit_load_args(j, 2, abi, args, regs);
+  jit_reloc_t r = jit_bxsubr_u(j, JIT_R0, JIT_R1);
+  jit_movi(j, JIT_R0, overflowed);
+  jit_patch_here(j, r);
+  jit_retr(j, JIT_R0);
+
+  intmax_t (*f)(intmax_t, intmax_t) = jit_end(j, NULL);
+
+  ASSERT(f(0, 0) == 0);
+  ASSERT(f(1, 1) == 0);
+  ASSERT(f(0, 1) == overflowed);
+  ASSERT(f(1, 0) == 1);
+
+#if __WORDSIZE == 32
+  ASSERT(f(0xffffffff, 0xffffffff) == 0);
+  ASSERT(f(0x7fffffff, 0) == 0x7fffffff);
+  ASSERT(f(0x7fffffff, 1) == 0x7ffffffe);
+  ASSERT(f(0x7fffffff, 0x7fffffff) == 0);
+  ASSERT(f(0x7fffffff, 0x80000000) == overflowed);
+  ASSERT(f(0x80000000, 0x80000000) == 0);
+#else
+  ASSERT(f(0xffffffffffffffff, 0xffffffffffffffff) == 0);
+  ASSERT(f(0x7fffffffffffffff, 0x7fffffffffffffff) == 0);
+  ASSERT(f(0x7fffffffffffffff, 0x8000000000000000) == overflowed);
+  ASSERT(f(0x8000000000000000, 0x8000000000000000) == 0);
+#endif
+}
+
+int
+main (int argc, char *argv[])
+{
+  return main_helper(argc, argv, run_test);
+}