Author: Armin Rigo <ar...@tunes.org>
Branch:
Changeset: r75482:cfeb96967bad
Date: 2015-01-22 13:37 +0100
http://bitbucket.org/pypy/pypy/changeset/cfeb96967bad/
Log: add comment
diff --git a/rpython/rtyper/lltypesystem/rordereddict.py
b/rpython/rtyper/lltypesystem/rordereddict.py
--- a/rpython/rtyper/lltypesystem/rordereddict.py
+++ b/rpython/rtyper/lltypesystem/rordereddict.py
@@ -46,6 +46,10 @@
@jit.oopspec('ordereddict.lookup(d, key, hash, flag)')
def ll_call_lookup_function(d, key, hash, flag):
fun = d.lookup_function_no & FUNC_MASK
+ # This likely() here forces gcc to compile the check for fun == FUNC_BYTE
+ # first. Otherwise, this is a regular switch and gcc (at least 4.7)
+ # compiles this as a series of checks, with the FUNC_BYTE case last.
+ # It sounds minor, but it is worth 6-7% on a PyPy microbenchmark.
if likely(fun == FUNC_BYTE):
return ll_dict_lookup(d, key, hash, flag, TYPE_BYTE)
elif fun == FUNC_SHORT:
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