1 files changed, 19 insertions, 25 deletions

diff --git a/dynasm/dasm_mips.lua b/dynasm/dasm_mips.lua
index aa33f0cc..c387d292 100644
--- a/dynasm/dasm_mips.lua
+++ b/dynasm/dasm_mips.lua
@@ -26,6 +26,8 @@ local _s = string
 local sub, format, byte, char = _s.sub, _s.format, _s.byte, _s.char
 local match, gmatch = _s.match, _s.gmatch
 local concat, sort = table.concat, table.sort
+local bit = bit or require("bit")
+local band, shl, sar, tohex = bit.band, bit.lshift, bit.arshift, bit.tohex
 
 -- Inherited tables and callbacks.
 local g_opt, g_arch
@@ -60,11 +62,6 @@ local secpos = 1
 
 ------------------------------------------------------------------------------
 
--- Return 8 digit hex number.
-local function tohex(x)
-  return sub(format("%08x", x), -8) -- Avoid 64 bit portability problem in Lua.
-end
-
 -- Dump action names and numbers.
 local function dumpactions(out)
   out:write("DynASM encoding engine action codes:\n")
@@ -639,16 +636,14 @@ end
 local function parse_imm(imm, bits, shift, scale, signed)
   local n = tonumber(imm)
   if n then
-    if n % 2^scale == 0 then
-      n = n / 2^scale
+    local m = sar(n, scale)
+    if shl(m, scale) == n then
       if signed then
-        if n >= 0 then
-          if n < 2^(bits-1) then return n*2^shift end
-        else
-          if n >= -(2^(bits-1))-1 then return (n+2^bits)*2^shift end
-        end
+        local s = sar(m, bits-1)
+        if s == 0 then return shl(m, shift)
+        elseif s == -1 then return shl(m + shl(1, bits), shift) end
       else
-        if n >= 0 and n <= 2^bits-1 then return n*2^shift end
+        if sar(m, bits) == 0 then return shl(m, shift) end
       end
     end
     werror("out of range immediate `"..imm.."'")
@@ -664,7 +659,7 @@ end
 local function parse_disp(disp)
   local imm, reg = match(disp, "^(.*)%(([%w_:]+)%)$")
   if imm then
-    local r = parse_gpr(reg)*2^21
+    local r = shl(parse_gpr(reg), 21)
     local extname = match(imm, "^extern%s+(%S+)$")
     if extname then
       waction("REL_EXT", map_extern[extname], nil, 1)
@@ -678,7 +673,7 @@ local function parse_disp(disp)
     local r, tp = parse_gpr(reg)
     if tp then
       waction("IMM", 32768+16*32, format(tp.ctypefmt, tailr))
-      return r*2^21
+      return shl(r, 21)
     end
   end
   werror("bad displacement `"..disp.."'")
@@ -689,7 +684,7 @@ local function parse_index(idx)
   if rt then
     rt = parse_gpr(rt)
     rs = parse_gpr(rs)
-    return rt*2^16 + rs*2^21
+    return shl(rt, 16) + shl(rs, 21)
   end
   werror("bad index `"..idx.."'")
 end
@@ -740,19 +735,19 @@ map_op[".template__"] = function(params, template, nparams)
   -- Process each character.
   for p in gmatch(sub(template, 9), ".") do
     if p == "D" then
-      op = op + parse_gpr(params[n]) * 2^11; n = n + 1
+      op = op + shl(parse_gpr(params[n]), 11); n = n + 1
     elseif p == "T" then
-      op = op + parse_gpr(params[n]) * 2^16; n = n + 1
+      op = op + shl(parse_gpr(params[n]), 16); n = n + 1
     elseif p == "S" then
-      op = op + parse_gpr(params[n]) * 2^21; n = n + 1
+      op = op + shl(parse_gpr(params[n]), 21); n = n + 1
     elseif p == "F" then
-      op = op + parse_fpr(params[n]) * 2^6; n = n + 1
+      op = op + shl(parse_fpr(params[n]), 6); n = n + 1
     elseif p == "G" then
-      op = op + parse_fpr(params[n]) * 2^11; n = n + 1
+      op = op + shl(parse_fpr(params[n]), 11); n = n + 1
     elseif p == "H" then
-      op = op + parse_fpr(params[n]) * 2^16; n = n + 1
+      op = op + shl(parse_fpr(params[n]), 16); n = n + 1
     elseif p == "R" then
-      op = op + parse_fpr(params[n]) * 2^21; n = n + 1
+      op = op + shl(parse_fpr(params[n]), 21); n = n + 1
     elseif p == "I" then
       op = op + parse_imm(params[n], 16, 0, 0, true); n = n + 1
     elseif p == "U" then
@@ -783,8 +778,7 @@ map_op[".template__"] = function(params, template, nparams)
     elseif p == "Z" then
       op = op + parse_imm(params[n], 10, 6, 0, false); n = n + 1
     elseif p == "=" then
-      local d = ((op - op % 2^11) / 2^11) % 32
-      op = op + d * 2^16 -- Copy D to T for clz, clo.
+      op = op + shl(band(op, 0xf800), 5) -- Copy D to T for clz, clo.
     else
       assert(false)
     end