Revert "Give variables the same names in ir and in lua"

This reverts commit c122bd1.

The reverted commit breaks variables reusing in generated code (see
sched_variables_helper()), so it was possible to reach 200 local
variables limit when trying to compile a large schema.

Added a test case.

Fixes #124.

Author: Totktonada

avro_schema/backend.lua

@@ -19,8 +19,6 @@ local random_bytes   = digest.base64_decode([[
 X1CntcveBDc4inHKyWfyXw5iCjg1f3TmeX88pZ2Galb9tXpTt1uBO0pZrkU5NW1/4Ki9g8fAwElq
 B3dRsBscsg==]])
 
--- The procedure gives ids to variables which then used to generate its names.
--- The general rule is to give the same number as it was in `ir` representation.
 local sched_variables_helper
 sched_variables_helper = function(block, n, varmap, reusequeue)
     for i = 1, #block do
@@ -33,7 +31,7 @@ sched_variables_helper = function(block, n, varmap, reusequeue)
                 var = n + 1
                 n = var
             end
-            varmap[o.ipv] = o.ipv
+            varmap[o.ipv] = var
         elseif o.op == opcode.ENDVAR then
             insert(reusequeue, varmap[o.ipv])
         end
@@ -598,43 +596,22 @@ emit_nested_block = function(ctx, block, cc, res)
     insert(queue, cc)
 end
 
--- The procedure emits local variables with names corresponding to their
--- register numbers in `ir` representation
-local function emit_locals(varmap, nservice_fields, res)
-    if nservice_fields then
-        -- Allocate variables for service_fields like this:
-        -- local sf1
-        -- local sf2 ...
-        for num = 1, nservice_fields do
-            insert(res, format('local sf%d', num))
-        end
-    end
-    local var_nums = {}
-    for _, num in pairs(varmap) do
-        table.insert(var_nums, num)
-    end
-    local pos = 0
-    -- generate batches like: local x1, x2, x3, x4
-    -- until it there are 4 or more variables still
-    while pos < #var_nums - 4 do
-        insert(res, format('local x%d, x%d, x%d, x%d',
-            var_nums[pos + 1],
-            var_nums[pos + 2],
-            var_nums[pos + 3],
-            var_nums[pos + 4]))
-        pos = pos + 4
-    end
-    -- emit variables by one if less then 4 left
-    while pos < #var_nums do
-        insert(res, format('local x%d',
-            var_nums[pos + 1]))
-        pos = pos + 1
-    end
-end
+local locals_tab = {
+    [0] = 'local x%d',
+    'local x%d, x%d',
+    'local x%d, x%d, x%d'
+}
 
 local function emit_func_body(il, func, nlocals_min, res)
-    local _, varmap = sched_func_variables(func)
-    emit_locals(varmap, nlocals_min, res)
+    local nlocals, varmap = sched_func_variables(func)
+    if nlocals_min and nlocals_min > nlocals then
+        nlocals = nlocals_min
+    end
+    for i = 1, nlocals, 4 do
+        insert(res, format(locals_tab[nlocals - i] or
+                           'local x%d, x%d, x%d, x%d',
+                           i, i+1, i+2, i+3))
+    end
     if il.enable_loop_peeling then
         peel_annotate(func, 0)
     end

avro_schema/init.lua

@@ -250,16 +250,16 @@ local function gen_fetch_service_fields(service_fields)
     local code = {}
     for i, field in ipairs(service_fields) do
         if field == 'boolean' then
-            insert(code, format('sf%d = r.t[%d] == 3', i, i))
+            insert(code, format('x%d = r.t[%d] == 3', i, i))
         elseif field == 'int' then
-            insert(code, format('sf%d = tonumber(r.v[%d].ival)', i, i))
+            insert(code, format('x%d = tonumber(r.v[%d].ival)', i, i))
         elseif field == 'long' then
-            insert(code, format('sf%d = r.v[%d].ival', i, i))
+            insert(code, format('x%d = r.v[%d].ival', i, i))
         elseif field == 'float' or field == 'double' then
-            insert(code, format('sf%d = r.v[%d].dval', i, i))
+            insert(code, format('x%d = r.v[%d].dval', i, i))
         elseif field == 'string' or field == 'bytes' then
             insert(code, format([[
-sf%d = ffi_string(r.b1-r.v[%d].xoff, r.v[%d].xlen)]], i, i, i))
+x%d = ffi_string(r.b1-r.v[%d].xoff, r.v[%d].xlen)]], i, i, i))
         else
             assert(false)
         end
@@ -345,7 +345,7 @@ r = rt_regs; v0 = 0; v1 = 0
 msgpack_data = decode_proc(r, data)
 r.b2 = ffi_cast("const uint8_t *", cpool) + #cpool]],
         conversion_complete = concat(u_complete, '\n'),
-        func_return = 'return v0' .. param_list(n, 'sf'),
+        func_return = 'return v0' .. param_list(n, 'x'),
         iter_prolog = 'if _ < 16 then goto continue end' -- artificially bump iter count
     })