[Bug middle-end/28831] [4.6/4.7/4.8 Regression] Aggregate copy not elided when using a return value as a pass-by-value parameter

[chip at pobox dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28831

--- Comment #17 from Chip Salzenberg <chip at pobox dot com> 2012-08-14 
22:50:01 UTC ---
The patch posted in Bug 20020 prevents missed optimization for 128-bit
structures on x86_64.  So this bug does seem to be all about the BLKmode.