transforms.dead_code_eliminator: also remove dead instructions.

artiq/compiler/transforms/dead_code_eliminator.py

@@ -14,12 +14,24 @@ class DeadCodeEliminator:
             self.process_function(func)
 
     def process_function(self, func):
+        modified = True
+        while modified:
+            modified = False
             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
+
+        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()