https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84486
Bug ID: 84486
Summary: code hoisting removes alignment assumption
Product: gcc
Version: 7.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: krebbel at gcc dot gnu.org
Target Milestone: ---
Created attachment 43473
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43473&action=edit
Autoreduced testcase
The __atomic_compare_exchange_n builtin on s390 uses the cdsg (compare and swap
double) instruction for 16 byte aligned operands and falls back to a library
call otherwise. Since the code hoisting change r238242 alignment hints applied
with __builtin_assume_aligned appear to get lost and we get a library call for
the attached testcase.
hardware instruction: -O1
libatomic call with: -O1 -fcode-hoisting
