test: add test for conversions folding

This patch adds the test for commit
1a40162 ("Fix assertions."). This patch
removes incorrect assertions in the fold optimizations for conversions
from numbers to different integer types. Since the issue affects only
branch 2.0, there is no need to fix it. Nevertheless, the test is
required to avoid regressions in the future.

Part of tarantool/tarantool#9145

test/tarantool-tests/lj-833-fold-conv-from-num.test.lua

@@ -0,0 +1,33 @@
+local tap = require('tap')
+
+-- XXX: Test the behaviour of fold optimizations from numbers to
+-- different integer types. The test itself doesn't fail before
+-- the commit since these changes relate only to version 2.0.
+
+local test = tap.test('lj-833-fold-conv-from-num'):skipcond({
+  ['Test requires JIT enabled'] = not jit.status(),
+})
+
+local ffi = require('ffi')
+
+test:plan(3)
+
+local arr_i64 = ffi.new('int64_t  [2]')
+local arr_u64 = ffi.new('uint64_t [2]')
+local arr_u32 = ffi.new('uint32_t [2]')
+
+jit.opt.start('hotloop=1')
+
+for _ = 1, 4 do
+  -- Test conversion to type (at store). Also, check the
+  -- conversion from number to int64_t at C array indexing.
+  arr_i64[1.1] = 1.1
+  arr_u64[1.1] = 1.1
+  arr_u32[1.1] = 1.1
+end
+
+test:is(arr_i64[1], 1LL,  'correct conversion to int64_t')
+test:is(arr_u64[1], 1ULL, 'correct conversion to uint64_t')
+test:is(arr_u32[1], 1ULL, 'correct conversion to uint32_t')
+
+test:done(true)