From 87c210d61706a689b47676758cab6e3c47f6b934 Mon Sep 17 00:00:00 2001
From: Connor Olding <cloningdonor@gmail.com>
Date: Sat, 23 Apr 2016 02:06:43 -0700
Subject: [PATCH] add .push/.pop directives for basic states

---
 README.md          |  4 ++++
 lips/Collector.lua |  6 ++++++
 lips/Dumper.lua    | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 lips/data.lua      |  1 +
 4 files changed, 58 insertions(+)

diff --git a/README.md b/README.md
index bf6a8b1..5e4cb48 100644
--- a/README.md
+++ b/README.md
@@ -224,6 +224,10 @@ defaults to 0x80000000.
 this allows you to have a PC value different from origin:
 `PC = origin + base`
 
+* `.push {vars...}` `.pop {vars...}'  
+pushes or pops variables with an internal stack.
+supported variables: org, base, pc.
+
 * `HEX { ... }`  
 write a series of bytes given in hexadecimal.
 all numbers must be given in hex — no prefix is required.
diff --git a/lips/Collector.lua b/lips/Collector.lua
index 3bd338d..1e5208e 100644
--- a/lips/Collector.lua
+++ b/lips/Collector.lua
@@ -85,6 +85,12 @@ function Collector:directive()
     end
     if name == 'ORG' or name == 'BASE' then
         add(name, self:const(nil, 'no labels'))
+    elseif name == 'PUSH' or name == 'POP' then
+        add(name, self:const())
+        while not self:is_EOL() do
+            self:optional_comma()
+            add(name, self:const())
+        end
     elseif name == 'ALIGN' or name == 'SKIP' then
         if self:is_EOL() and name == 'ALIGN' then
             add(name)
diff --git a/lips/Dumper.lua b/lips/Dumper.lua
index 6a2d320..a568fa0 100644
--- a/lips/Dumper.lua
+++ b/lips/Dumper.lua
@@ -1,6 +1,7 @@
 local floor = math.floor
 local format = string.format
 local insert = table.insert
+local remove = table.remove
 local unpack = unpack or table.unpack
 
 local path = string.gsub(..., "[^.]+$", "")
@@ -276,6 +277,7 @@ function Dumper:pc()
 end
 
 function Dumper:load(statements)
+    local valstack = {} -- for .push/.pop directives
     local new_statements = {}
     self.pos = 0
     self.base = 0
@@ -296,6 +298,51 @@ function Dumper:load(statements)
             elseif s.type == '!BASE' then
                 self.base = s[1].tok
                 insert(new_statements, s)
+            elseif s.type == '!PUSH' or s.type == '!POP' then
+                local thistype = s.type:sub(2):lower()
+                for i, t in ipairs(s) do
+                    local name = t.tok
+                    if type(name) ~= 'string' then
+                        self:error('expected state to '..thistype, name)
+                    end
+
+                    name = name:lower()
+                    local pushing = s.type == '!PUSH'
+                    if name == 'org' then
+                        if pushing then
+                            insert(valstack, self.pos)
+                        else
+                            self.pos = remove(valstack)
+                        end
+                    elseif name == 'base' then
+                        if pushing then
+                            insert(valstack, self.base)
+                        else
+                            self.base = remove(valstack)
+                        end
+                    elseif name == 'pc' then
+                        if pushing then
+                            insert(valstack, self.pos)
+                            insert(valstack, self.base)
+                        else
+                            self.base = remove(valstack)
+                            self.pos = remove(valstack)
+                        end
+                    else
+                        self:error('unknown state to '..thistype, name)
+                    end
+
+                    if self.pos == nil or self.base == nil then
+                        self:error('ran out of values to pop')
+                    end
+
+                    if not pushing then
+                        local s = Statement(self.fn, self.line, '!ORG', self.pos)
+                        insert(new_statements, s)
+                        local s = Statement(self.fn, self.line, '!BASE', self.base)
+                        insert(new_statements, s)
+                    end
+                end
             elseif s.type == '!ALIGN' or s.type == '!SKIP' then
                 local length, content
                 if s.type == '!ALIGN' then
diff --git a/lips/data.lua b/lips/data.lua
index b693848..2ce6444 100644
--- a/lips/data.lua
+++ b/lips/data.lua
@@ -30,6 +30,7 @@ data.fpu_registers = {
 
 data.all_directives = {
     'ORG', 'BASE', 'ALIGN', 'SKIP',
+    'PUSH', 'POP', -- experimental
     'ASCII', 'ASCIIZ',
     'BYTE', 'HALFWORD', 'WORD',
     --'HEX', -- excluded here due to different syntax