From 75f07eb9ef019356dfb7118482e8cab33d073678 Mon Sep 17 00:00:00 2001
From: Michael Nolan <mtnolan2640@gmail.com>
Date: Tue, 5 May 2020 15:58:34 -0400
Subject: [PATCH] Add rudimentary branch capability

---
 src/soc/decoder/isa/caller.py      |  5 +++--
 src/soc/decoder/isa/test_caller.py | 19 ++++++++++++++++++-
 src/soc/decoder/pseudo/pywriter.py |  2 ++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/soc/decoder/isa/caller.py b/src/soc/decoder/isa/caller.py
index 81a294d2..03503330 100644
--- a/src/soc/decoder/isa/caller.py
+++ b/src/soc/decoder/isa/caller.py
@@ -121,7 +121,7 @@ class PC:
         self.NIA = self.CIA + SelectableInt(4, 64)
 
     def update(self, namespace):
-        self.CIA = self.NIA
+        self.CIA = namespace['NIA'].narrow(64)
         self.NIA = self.CIA + SelectableInt(4, 64)
         namespace['CIA'] = self.CIA
         namespace['NIA'] = self.NIA
@@ -160,6 +160,7 @@ class ISACaller:
                           'NIA': self.pc.NIA,
                           'CIA': self.pc.CIA,
                           'CR': self.cr,
+                          'LR': self.undefined,
                           'undefined': self.undefined,
                           }
 
@@ -246,8 +247,8 @@ def inject():
             context = args[0].namespace
             saved_values = func_globals.copy()  # Shallow copy of dict.
             func_globals.update(context)
-
             result = func(*args, **kwargs)
+            args[0].namespace = func_globals
             #exec (func.__code__, func_globals)
 
             #finally:
diff --git a/src/soc/decoder/isa/test_caller.py b/src/soc/decoder/isa/test_caller.py
index 0c5ec46a..5d4869fa 100644
--- a/src/soc/decoder/isa/test_caller.py
+++ b/src/soc/decoder/isa/test_caller.py
@@ -33,7 +33,11 @@ class DecoderTestCase(FHDLTestCase):
         gen = generator.generate_instructions()
 
         def process():
-            for ins, code in zip(gen, generator.assembly.splitlines()):
+            instructions = list(zip(gen, generator.assembly.splitlines()))
+
+            index = simulator.pc.CIA.value//4
+            while index < len(instructions):
+                ins, code = instructions[index]
 
                 print("0x{:X}".format(ins & 0xffffffff))
                 print(code)
@@ -44,6 +48,7 @@ class DecoderTestCase(FHDLTestCase):
                 yield Delay(1e-6)
                 opname = code.split(' ')[0]
                 yield from simulator.call(opname)
+                index = simulator.pc.CIA.value//4
 
         sim.add_process(process)
         with sim.write_vcd("simulator.vcd", "simulator.gtkw",
@@ -89,6 +94,18 @@ class DecoderTestCase(FHDLTestCase):
             self.assertEqual(sim.gpr(2), SelectableInt(0x10008, 64))
             self.assertEqual(sim.gpr(3), SelectableInt(0x1000c, 64))
 
+    def test_branch(self):
+        lst = ["ba 0xc",             # branch to line 4
+               "addi 1, 0, 0x1234",  # Should never execute
+               "ba 0x1000",          # exit the program
+               "addi 2, 0, 0x1234",  # line 4
+               "ba 0x8"]             # branch to line 3
+        with Program(lst) as program:
+            sim = self.run_tst_program(program)
+            self.assertEqual(sim.pc.CIA, SelectableInt(0x1000, 64))
+            self.assertEqual(sim.gpr(1), SelectableInt(0x0, 64))
+            self.assertEqual(sim.gpr(2), SelectableInt(0x1234, 64))
+
     @unittest.skip("broken")  # FIXME
     def test_mtcrf(self):
         for i in range(4):
diff --git a/src/soc/decoder/pseudo/pywriter.py b/src/soc/decoder/pseudo/pywriter.py
index 922de376..abdf9940 100644
--- a/src/soc/decoder/pseudo/pywriter.py
+++ b/src/soc/decoder/pseudo/pywriter.py
@@ -64,6 +64,8 @@ class PyISAWriter(ISA):
                 op_fname ="op_%s" % page.replace(".", "_")
                 f.write("    @inject()\n")
                 f.write("    def %s(%s):\n" % (op_fname, args))
+                if 'NIA' in pycode:  # HACK - TODO fix
+                    f.write("        global NIA\n")
                 pycode = pycode.split("\n")
                 pycode = '\n'.join(map(lambda x: "        %s" % x, pycode))
                 pycode = pycode.rstrip()
-- 
2.30.2