diff options
Diffstat (limited to 'miasm2/analysis/ssa.py')
| -rw-r--r-- | miasm2/analysis/ssa.py | 51 |
1 files changed, 44 insertions, 7 deletions
diff --git a/miasm2/analysis/ssa.py b/miasm2/analysis/ssa.py index ea3189eb..501cdd5e 100644 --- a/miasm2/analysis/ssa.py +++ b/miasm2/analysis/ssa.py @@ -1,9 +1,46 @@ from collections import deque -from miasm2.expression.expression import ExprId, ExprAssign, ExprOp, get_expr_ids +from miasm2.expression.expression import ExprId, ExprAssign, ExprOp, \ + ExprLoc, get_expr_ids from miasm2.ir.ir import AssignBlock, IRBlock +def sanitize_graph_head(ircfg, head): + """ + In multiple algorithm, the @head of the ircfg may not have predecessors. + The function transform the @ircfg in order to ensure this property + @ircfg: IRCFG instance + @head: the location of the graph's head + """ + + if not ircfg.predecessors(head): + return + original_edges = ircfg.predecessors(head) + sub_head = ircfg.loc_db.add_location() + + # Duplicate graph, replacing references to head by sub_head + replaced_expr = { + ExprLoc(head, ircfg.IRDst.size): + ExprLoc(sub_head, ircfg.IRDst.size) + } + ircfg.simplify( + lambda expr:expr.replace_expr(replaced_expr) + ) + # Duplicate head block + ircfg.add_irblock(IRBlock(sub_head, list(ircfg.blocks[head]))) + + # Remove original head block + ircfg.del_node(head) + + for src in original_edges: + ircfg.add_edge(src, sub_head) + + # Create new head, jumping to sub_head + assignblk = AssignBlock({ircfg.IRDst:ExprLoc(sub_head, ircfg.IRDst.size)}) + new_irblock = IRBlock(head, [assignblk]) + ircfg.add_irblock(new_irblock) + + class SSA(object): """ Generic class for static single assignment (SSA) transformation @@ -366,6 +403,7 @@ class SSADiGraph(SSA): def transform(self, head): """Transforms into SSA""" + sanitize_graph_head(self.graph, head) self._init_variable_defs(head) self._place_phi(head) self._rename(head) @@ -595,10 +633,11 @@ class SSADiGraph(SSA): # Replace non modified node used in phi with new variable self.ircfg.simplify(lambda expr:expr.replace_expr(var_to_newname)) - irblock = self.ircfg.blocks[head] - assignblks = list(irblock) - assignblks[0:0] = [AssignBlock(newname_to_var, assignblks[0].instr)] - self.ircfg.blocks[head] = IRBlock(head, assignblks) + if newname_to_var: + irblock = self.ircfg.blocks[head] + assignblks = list(irblock) + assignblks[0:0] = [AssignBlock(newname_to_var, assignblks[0].instr)] + self.ircfg.blocks[head] = IRBlock(head, assignblks) # Updt structure for loc_key in self._phinodes: @@ -612,7 +651,6 @@ class SSADiGraph(SSA): for newname, var in newname_to_var.iteritems(): self.ssa_to_location[newname] = head, 0 self.ssa_variable_to_expr[newname] = var - self.immutable_ids.add(newname) self.expressions[newname] = var @@ -718,7 +756,6 @@ class UnSSADiGraph(object): self.insert_parallel_copy() self.replace_merge_sets() self.remove_assign_eq() - remove_empty_assignblks(self.ssa.graph) def insert_parallel_copy(self): """ |