Simplification: Fix 'A op 0' with op == '-' bug, add corresponding test case

2 files changed, 8 insertions, 1 deletions

diff --git a/miasm2/expression/simplifications_common.py b/miasm2/expression/simplifications_common.py
index 208870eb..58cabaf4 100644
--- a/miasm2/expression/simplifications_common.py
+++ b/miasm2/expression/simplifications_common.py
@@ -92,9 +92,14 @@ def simp_cst_propagation(e_s, e):
     if op == '-' and len(args) == 1 and isinstance(args[0], ExprInt):
         return ExprInt(-args[0].arg)
     # A op 0 =>A
-    if op in ['+', '-', '|', "^", "<<", ">>", "<<<", ">>>"] and len(args) > 1:
+    if op in ['+', '|', "^", "<<", ">>", "<<<", ">>>"] and len(args) > 1:
         if isinstance(args[-1], ExprInt) and args[-1].arg == 0:
             args.pop()
+    # A - 0 =>A
+    if op == '-' and len(args) > 1 and args[-1].arg == 0:
+        assert(len(args) == 2) # Op '-' with more than 2 args: SantityCheckError
+        return args[0]
+
     # A * 1 =>A
     if op == "*" and len(args) > 1:
         if isinstance(args[-1], ExprInt) and args[-1].arg == 1:
diff --git a/test/expression/simplifications.py b/test/expression/simplifications.py
index 6b437218..0f217c72 100644
--- a/test/expression/simplifications.py
+++ b/test/expression/simplifications.py
@@ -155,6 +155,8 @@ to_test = [(ExprInt32(1) - ExprInt32(1), ExprInt32(0)),
     (a & b & ExprInt_fromsize(a.size, -1), a & b),
     (a | b | ExprInt_fromsize(a.size, -1),
      ExprInt_fromsize(a.size, -1)),
+    (ExprOp('-', ExprInt8(1), ExprInt8(0)),
+     ExprInt8(1)),
 ]
 
 for e, e_check in to_test[:]: