added ability to iterate over basic block's predecessors

llvmlite/ir/builder.py

@@ -822,12 +822,17 @@ def switch(self, value, default):
         self._set_terminator(swt)
         return swt
 
+    def add_pred(self, block):
+        if self.basic_block not in block.predecessors:
+            block.predecessors.append(self.basic_block)
+
     def branch(self, target):
         """
         Unconditional branch to *target*.
         """
         br = instructions.Branch(self.block, "br", [target])
         self._set_terminator(br)
+        self.add_pred(target)
         return br
 
     def cbranch(self, cond, truebr, falsebr):
@@ -837,6 +842,8 @@ def cbranch(self, cond, truebr, falsebr):
         br = instructions.ConditionalBranch(self.block, "br",
                                             [cond, truebr, falsebr])
         self._set_terminator(br)
+        self.add_pred(truebr)
+        self.add_pred(falsebr)
         return br
 
     def branch_indirect(self, addr):

llvmlite/ir/values.py

@@ -788,11 +788,15 @@ def __init__(self, parent, name=''):
         self.scope = parent.scope
         self.instructions = []
         self.terminator = None
+        self.predecessors = []
 
     @property
     def is_terminated(self):
         return self.terminator is not None
 
+    def has_predecessors(self):
+        return len(self.predecessors) > 0
+
     @property
     def function(self):
         return self.parent