[pypy-commit] pypy default: (cfbolz, smarr): optimize int_sub_ovf(x, x) to 0

[Stefan Marr]

Author: Stefan Marr <hg at stefan-marr.de>
Branch: 
Changeset: r71628:919ab79173d3
Date: 2014-05-21 11:33 +0100
http://bitbucket.org/pypy/pypy/changeset/919ab79173d3/

Log:	(cfbolz, smarr): optimize int_sub_ovf(x, x) to 0

diff --git a/rpython/jit/metainterp/optimizeopt/intbounds.py b/rpython/jit/metainterp/optimizeopt/intbounds.py
--- a/rpython/jit/metainterp/optimizeopt/intbounds.py
+++ b/rpython/jit/metainterp/optimizeopt/intbounds.py
@@ -198,11 +198,11 @@
             opnum = lastop.getopnum()
             args = lastop.getarglist()
             result = lastop.result
-            # If the INT_xxx_OVF was replaced with INT_xxx, then we can kill
-            # the GUARD_NO_OVERFLOW.
-            if (opnum == rop.INT_ADD or
-                opnum == rop.INT_SUB or
-                opnum == rop.INT_MUL):
+            # If the INT_xxx_OVF was replaced with INT_xxx or removed
+            # completely, then we can kill the GUARD_NO_OVERFLOW.
+            if (opnum != rop.INT_ADD_OVF and
+                opnum != rop.INT_SUB_OVF and
+                opnum != rop.INT_MUL_OVF):
                 return
             # Else, synthesize the non overflowing op for optimize_default to
             # reuse, as well as the reverse op
@@ -248,6 +248,9 @@
     def optimize_INT_SUB_OVF(self, op):
         v1 = self.getvalue(op.getarg(0))
         v2 = self.getvalue(op.getarg(1))
+        if v1 is v2:
+            self.make_constant_int(op.result, 0)
+            return
         resbound = v1.intbound.sub_bound(v2.intbound)
         if resbound.bounded():
             op = op.copy_and_change(rop.INT_SUB)
diff --git a/rpython/jit/metainterp/optimizeopt/test/test_optimizeopt.py b/rpython/jit/metainterp/optimizeopt/test/test_optimizeopt.py
--- a/rpython/jit/metainterp/optimizeopt/test/test_optimizeopt.py
+++ b/rpython/jit/metainterp/optimizeopt/test/test_optimizeopt.py
@@ -3339,6 +3339,21 @@
         """
         self.optimize_loop(ops, expected)
 
+    def test_fold_int_sub_ovf_xx(self):
+        ops = """
+        [i0]
+        i1 = int_sub_ovf(i0, i0)
+        guard_no_overflow() []
+        escape(i1)
+        jump(i1)
+        """
+        expected = """
+        []
+        escape(0)
+        jump()
+        """
+        self.optimize_loop(ops, expected)
+
     def test_fold_partially_constant_shift(self):
         ops = """
         [i0]