From: Raymond Hettinger <python@rcn.com>
Date: Sun, 20 Feb 2005 12:46:54 +0000 (+0000)
Subject: Teach the peepholer to fold unary operations on constants.
X-Git-Tag: v2.5a0~2005
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=afd842f5b262bfe5e2e2e53762d748b5da6caf2c;p=thirdparty%2FPython%2Fcpython.git

Teach the peepholer to fold unary operations on constants.

Afterwards, -0.5 loads in a single step and no longer requires a runtime
UNARY_NEGATIVE operation.
---

diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 34bd99f2a402..4385a84c1fbf 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -133,6 +133,25 @@ class TestTranforms(unittest.TestCase):
         asm = dis_single('a="x"*1000')
         self.assert_('(1000)' in asm)
 
+    def test_folding_of_unaryops_on_constants(self):
+        for line, elem in (
+            ('`1`', "('1')"),                       # unary convert
+            ('-0.5', '(-0.5)'),                     # unary negative
+            ('~-2', '(1)'),                         # unary invert
+        ):
+            asm = dis_single(line)
+            self.assert_(elem in asm, asm)
+            self.assert_('UNARY_' not in asm)
+
+        # Verify that unfoldables are skipped
+        for line, elem in (
+            ('-"abc"', "('abc')"),                  # unary negative
+            ('~"abc"', "('abc')"),                  # unary invert
+        ):
+            asm = dis_single(line)
+            self.assert_(elem in asm, asm)
+            self.assert_('UNARY_' in asm)
+
     def test_elim_extra_return(self):
         # RETURN LOAD_CONST None RETURN  -->  RETURN
         def f(x):