First implementation of constant propagation

Local constant variables initialized with compile-time constants
are optimized away from the code.

4 files changed, 89 insertions, 42 deletions

diff --git a/testes/code.lua b/testes/code.lua
index 128ca2cb..49d682f8 100644
--- a/testes/code.lua
+++ b/testes/code.lua
@@ -7,6 +7,22 @@ if T==nil then
 end
 print "testing code generation and optimizations"
 
+-- to test constant propagation
+local <const> k0 = 0
+local <const> k1 = 1
+local <const> k3 = 3
+local <const> k6 = k3 + (k3 << k0)
+local <const> kFF0 = 0xFF0
+local <const> k3_78 = 3.78
+local <const> x, <const> k3_78_4 = 10, k3_78 / 4
+assert(x == 10)
+
+local <const> kx = "x"
+
+local <const> kTrue = true
+local <const> kFalse = false
+
+local <const> kNil = nil
 
 -- this code gave an error for the code checker
 do
@@ -27,12 +43,12 @@ end
 
 local function foo ()
   local a
-  a = 3;
+  a = k3;
   a = 0; a = 0.0; a = -7 + 7
-  a = 3.78/4; a = 3.78/4
-  a = -3.78/4; a = 3.78/4; a = -3.78/4
+  a = k3_78/4; a = k3_78_4
+  a = -k3_78/4; a = k3_78/4; a = -3.78/4
   a = -3.79/4; a = 0.0; a = -0;
-  a = 3; a = 3.0; a = 3; a = 3.0
+  a = k3; a = 3.0; a = 3; a = 3.0
 end
 
 checkKlist(foo, {3.78/4, -3.78/4, -3.79/4})
@@ -86,10 +102,11 @@ end, 'CLOSURE', 'NEWTABLE', 'GETTABUP', 'CALL', 'SETLIST', 'CALL', 'RETURN')
 
 -- sequence of LOADNILs
 check(function ()
+  local <const> kNil = nil
   local a,b,c
   local d; local e;
   local f,g,h;
-  d = nil; d=nil; b=nil; a=nil; c=nil;
+  d = nil; d=nil; b=nil; a=kNil; c=nil;
 end, 'LOADNIL', 'RETURN0')
 
 check(function ()
@@ -109,7 +126,7 @@ check (function (a,b,c) return a end, 'RETURN1')
 
 
 -- infinite loops
-check(function () while true do local a = -1 end end,
+check(function () while kTrue do local a = -1 end end,
 'LOADI', 'JMP', 'RETURN0')
 
 check(function () while 1 do local a = -1 end end,
@@ -125,9 +142,9 @@ check(function (a,b,c,d) return a..b..c..d end,
 
 -- not
 check(function () return not not nil end, 'LOADBOOL', 'RETURN1')
-check(function () return not not false end, 'LOADBOOL', 'RETURN1')
+check(function () return not not kFalse end, 'LOADBOOL', 'RETURN1')
 check(function () return not not true end, 'LOADBOOL', 'RETURN1')
-check(function () return not not 1 end, 'LOADBOOL', 'RETURN1')
+check(function () return not not k3 end, 'LOADBOOL', 'RETURN1')
 
 -- direct access to locals
 check(function ()
@@ -144,7 +161,8 @@ end,
 -- direct access to constants
 check(function ()
   local a,b
-  a.x = 3.2
+  local c = kNil
+  a[kx] = 3.2
   a.x = b
   a[b] = 'x'
 end,
@@ -152,8 +170,9 @@ end,
 
 -- "get/set table" with numeric indices
 check(function (a)
+  local <const> k255 = 255
   a[1] = a[100]
-  a[255] = a[256]
+  a[k255] = a[256]
   a[256] = 5
 end,
   'GETI', 'SETI',
@@ -170,7 +189,7 @@ end,
 
 check(function ()
   local a,b
-  a[true] = false
+  a[kTrue] = false
 end,
   'LOADNIL', 'LOADBOOL', 'SETTABLE', 'RETURN0')
 
@@ -238,37 +257,39 @@ local function checkF (func, val)
 end
 
 checkF(function () return 0.0 end, 0.0)
-checkI(function () return 0 end, 0)
-checkI(function () return -0//1 end, 0)
+checkI(function () return k0 end, 0)
+checkI(function () return -k0//1 end, 0)
 checkK(function () return 3^-1 end, 1/3)
 checkK(function () return (1 + 1)^(50 + 50) end, 2^100)
 checkK(function () return (-2)^(31 - 2) end, -0x20000000 + 0.0)
-checkF(function () return (-3^0 + 5) // 3.0 end, 1.0)
-checkI(function () return -3 % 5 end, 2)
+checkF(function () return (-k3^0 + 5) // 3.0 end, 1.0)
+checkI(function () return -k3 % 5 end, 2)
 checkF(function () return -((2.0^8 + -(-1)) % 8)/2 * 4 - 3 end, -5.0)
 checkF(function () return -((2^8 + -(-1)) % 8)//2 * 4 - 3 end, -7.0)
 checkI(function () return 0xF0.0 | 0xCC.0 ~ 0xAA & 0xFD end, 0xF4)
-checkI(function () return ~(~0xFF0 | 0xFF0) end, 0)
+checkI(function () return ~(~kFF0 | kFF0) end, 0)
 checkI(function () return ~~-1024.0 end, -1024)
-checkI(function () return ((100 << 6) << -4) >> 2 end, 100)
+checkI(function () return ((100 << k6) << -4) >> 2 end, 100)
 
 -- borders around MAXARG_sBx ((((1 << 17) - 1) >> 1) == 65535)
 local a = 17; local sbx = ((1 << a) - 1) >> 1   -- avoid folding
-checkI(function () return 65535 end, sbx)
-checkI(function () return -65535 end, -sbx)
-checkI(function () return 65536 end, sbx + 1)
-checkK(function () return 65537 end, sbx + 2)
-checkK(function () return -65536 end, -(sbx + 1))
+local <const> border = 65535
+checkI(function () return border end, sbx)
+checkI(function () return -border end, -sbx)
+checkI(function () return border + 1 end, sbx + 1)
+checkK(function () return border + 2 end, sbx + 2)
+checkK(function () return -(border + 1) end, -(sbx + 1))
 
-checkF(function () return 65535.0 end, sbx + 0.0)
-checkF(function () return -65535.0 end, -sbx + 0.0)
-checkF(function () return 65536.0 end, (sbx + 1.0))
-checkK(function () return 65537.0 end, (sbx + 2.0))
-checkK(function () return -65536.0 end, -(sbx + 1.0))
+local <const> border = 65535.0
+checkF(function () return border end, sbx + 0.0)
+checkF(function () return -border end, -sbx + 0.0)
+checkF(function () return border + 1 end, (sbx + 1.0))
+checkK(function () return border + 2 end, (sbx + 2.0))
+checkK(function () return -(border + 1) end, -(sbx + 1.0))
 
 
 -- immediate operands
-checkR(function (x) return x + 1 end, 10, 11, 'ADDI', 'RETURN1')
+checkR(function (x) return x + k1 end, 10, 11, 'ADDI', 'RETURN1')
 checkR(function (x) return 128 + x end, 0.0, 128.0, 'ADDI', 'RETURN1')
 checkR(function (x) return x * -127 end, -1.0, 127.0, 'MULI', 'RETURN1')
 checkR(function (x) return 20 * x end, 2, 40, 'MULI', 'RETURN1')
@@ -276,7 +297,7 @@ checkR(function (x) return x ^ -2 end, 2, 0.25, 'POWI', 'RETURN1')
 checkR(function (x) return x / 40 end, 40, 1.0, 'DIVI', 'RETURN1')
 checkR(function (x) return x // 1 end, 10.0, 10.0, 'IDIVI', 'RETURN1')
 checkR(function (x) return x % (100 - 10) end, 91, 1, 'MODI', 'RETURN1')
-checkR(function (x) return 1 << x end, 3, 8, 'SHLI', 'RETURN1')
+checkR(function (x) return k1 << x end, 3, 8, 'SHLI', 'RETURN1')
 checkR(function (x) return x << 2 end, 10, 40, 'SHRI', 'RETURN1')
 checkR(function (x) return x >> 2 end, 8, 2, 'SHRI', 'RETURN1')
 checkR(function (x) return x & 1 end, 9, 1, 'BANDK', 'RETURN1')
@@ -295,7 +316,7 @@ checkR(function (x) return x % (100.0 - 10) end, 91, 1.0, 'MODK', 'RETURN1')
 
 -- no foldings (and immediate operands)
 check(function () return -0.0 end, 'LOADF', 'UNM', 'RETURN1')
-check(function () return 3/0 end, 'LOADI', 'DIVI', 'RETURN1')
+check(function () return k3/0 end, 'LOADI', 'DIVI', 'RETURN1')
 check(function () return 0%0 end, 'LOADI', 'MODI', 'RETURN1')
 check(function () return -4//0 end, 'LOADI', 'IDIVI', 'RETURN1')
 check(function (x) return x >> 2.0 end, 'LOADF', 'SHR', 'RETURN1')
@@ -335,7 +356,7 @@ end,
 
 do   -- tests for table access in upvalues
   local t
-  check(function () t.x = t.y end, 'GETTABUP', 'SETTABUP')
+  check(function () t[kx] = t.y end, 'GETTABUP', 'SETTABUP')
   check(function (a) t[a()] = t[a()] end,
   'MOVE', 'CALL', 'GETUPVAL', 'MOVE', 'CALL',
   'GETUPVAL', 'GETTABLE', 'SETTABLE')
@@ -379,6 +400,12 @@ function (a)
 end
 )
 
+checkequal(function () return 6 or true or nil end,
+           function () return k6 or kTrue or kNil end)
+
+checkequal(function () return 6 and true or nil end,
+           function () return k6 and kTrue or kNil end)
+
 
 print 'OK'
 
diff --git a/testes/constructs.lua b/testes/constructs.lua
index fe4db2cb..8a549e10 100644
--- a/testes/constructs.lua
+++ b/testes/constructs.lua
@@ -287,7 +287,7 @@ a,b = F(nil)==nil; assert(a == true and b == nil)
 ------------------------------------------------------------------
 
 -- sometimes will be 0, sometimes will not...
-_ENV.GLOB1 = math.floor(os.time()) % 2
+_ENV.GLOB1 = math.random(0, 1)
 
 -- basic expressions with their respective values
 local basiccases = {
@@ -298,6 +298,26 @@ local basiccases = {
   {"(0==_ENV.GLOB1)", 0 == _ENV.GLOB1},
 }
 
+local prog
+
+if _ENV.GLOB1 == 0 then
+  basiccases[2][1] = "F"   -- constant false
+
+  prog = [[
+    local <const> F = false
+    if %s then IX = true end
+    return %s
+]]
+else
+  basiccases[4][1] = "k10"   -- constant 10
+
+  prog = [[
+    local <const> k10 = 10
+    if %s then IX = true end
+    return %s
+  ]]
+end
+
 print('testing short-circuit optimizations (' .. _ENV.GLOB1 .. ')')
 
 
@@ -337,8 +357,6 @@ cases[1] = basiccases
 for i = 2, level do cases[i] = createcases(i) end
 print("+")
 
-local prog = [[if %s then IX = true end; return %s]]
-
 local i = 0
 for n = 1, level do
   for _, v in pairs(cases[n]) do
diff --git a/testes/locals.lua b/testes/locals.lua
index 0de00a98..1b82dd7f 100644
--- a/testes/locals.lua
+++ b/testes/locals.lua
@@ -324,7 +324,7 @@ do
 
   -- errors due to non-closable values
   local function foo ()
-    local <toclose> x = 34
+    local <toclose> x = {}
   end
   local stat, msg = pcall(foo)
   assert(not stat and string.find(msg, "variable 'x'"))
diff --git a/testes/math.lua b/testes/math.lua
index c45a91ad..befce12e 100644
--- a/testes/math.lua
+++ b/testes/math.lua
@@ -270,7 +270,7 @@ else
 end
 
 do
-  local NaN = 0/0
+  local <const> NaN = 0/0
   assert(not (NaN < 0))
   assert(not (NaN > minint))
   assert(not (NaN <= -9))
@@ -767,7 +767,8 @@ assert(a == '10' and b == '20')
 
 do
   print("testing -0 and NaN")
-  local mz, z = -0.0, 0.0
+  local <const> mz = -0.0
+  local <const> z = 0.0
   assert(mz == z)
   assert(1/mz < 0 and 0 < 1/z)
   local a = {[mz] = 1}
@@ -775,17 +776,18 @@ do
   a[z] = 2
   assert(a[z] == 2 and a[mz] == 2)
   local inf = math.huge * 2 + 1
-  mz, z = -1/inf, 1/inf
+  local <const> mz = -1/inf
+  local <const> z = 1/inf
   assert(mz == z)
   assert(1/mz < 0 and 0 < 1/z)
-  local NaN = inf - inf
+  local <const> NaN = inf - inf
   assert(NaN ~= NaN)
   assert(not (NaN < NaN))
   assert(not (NaN <= NaN))
   assert(not (NaN > NaN))
   assert(not (NaN >= NaN))
   assert(not (0 < NaN) and not (NaN < 0))
-  local NaN1 = 0/0
+  local <const> NaN1 = 0/0
   assert(NaN ~= NaN1 and not (NaN <= NaN1) and not (NaN1 <= NaN))
   local a = {}
   assert(not pcall(rawset, a, NaN, 1))
@@ -814,8 +816,8 @@ end
 -- the first call after seed 1007 should return 0x7a7040a5a323c9d6
 do
   -- all computations assume at most 32-bit integers
-  local h = 0x7a7040a5   -- higher half
-  local l = 0xa323c9d6   -- lower half
+  local <const> h = 0x7a7040a5   -- higher half
+  local <const> l = 0xa323c9d6   -- lower half
 
   math.randomseed(1007)
   -- get the low 'intbits' of the 64-bit expected result