[Bug libitm/68591] New: trans-mem: missing transactional read in transaction when using -O1

["torvald at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68591

            Bug ID: 68591
           Summary: trans-mem: missing transactional read in transaction
                    when using -O1
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libitm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: torvald at gcc dot gnu.org
  Target Milestone: ---

Created attachment 36860
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36860&action=edit
test case

The attached test case miscompiles in that it does not transform the load from
ptr in the conditional in the transaction into a transactional load.  Instead,
it seems to assume that ptr's value is fixed and not shared with other threads.
 This changes when the synchronization that could potentially make it share
gets inlined into the function with the transaction.  For simplicity, this is a
single-threaded test, but I discovered that in a multi-threaded setting.