From 5dd1fc993e194de2f985dd3b21fd1d45e26df24f Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Wed, 16 Dec 2015 23:38:55 +0800
Subject: [PATCH] transforms.dead_code_eliminator: also remove dead
 instructions.

---
 .../transforms/dead_code_eliminator.py        | 29 +++++++++++++++----
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/artiq/compiler/transforms/dead_code_eliminator.py b/artiq/compiler/transforms/dead_code_eliminator.py
index dfe5ccf6c..9c5a54bb0 100644
--- a/artiq/compiler/transforms/dead_code_eliminator.py
+++ b/artiq/compiler/transforms/dead_code_eliminator.py
@@ -14,12 +14,24 @@ class DeadCodeEliminator:
             self.process_function(func)
 
     def process_function(self, func):
-        for block in list(func.basic_blocks):
-            if not any(block.predecessors()) and block != func.entry():
-                for use in set(block.uses):
-                    if isinstance(use, ir.SetLocal):
-                        use.erase()
-                self.remove_block(block)
+        modified = True
+        while modified:
+            modified = False
+            for block in list(func.basic_blocks):
+                if not any(block.predecessors()) and block != func.entry():
+                    self.remove_block(block)
+                    modified = True
+
+        modified = True
+        while modified:
+            modified = False
+            for insn in func.instructions():
+                if isinstance(insn, (ir.Phi, ir.Alloc, ir.GetLocal, ir.GetConstructor,
+                                     ir.GetAttr, ir.GetElem, ir.Coerce, ir.Arith,
+                                     ir.Compare, ir.Closure, ir.Select, ir.Quote)) \
+                        and not any(insn.uses):
+                    insn.erase()
+                    modified = True
 
     def remove_block(self, block):
         # block.uses are updated while iterating
@@ -28,6 +40,9 @@ class DeadCodeEliminator:
                 use.remove_incoming_block(block)
                 if not any(use.operands):
                     self.remove_instruction(use)
+            elif isinstance(use, ir.SetLocal):
+                # setlocal %env, %block is only used for lowering finally
+                use.erase()
             else:
                 assert False
 
@@ -39,5 +54,7 @@ class DeadCodeEliminator:
                 use.remove_incoming_value(insn)
                 if not any(use.operands):
                     self.remove_instruction(use)
+            else:
+                assert False
 
         insn.erase()