[Bug rtl-optimization/63637] New: CSE() on x86 asm()-s no longer working due to PR/60663 fix

[jbeulich at novell dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63637

            Bug ID: 63637
           Summary: CSE() on x86 asm()-s no longer working due to PR/60663
                    fix
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jbeulich at novell dot com

Created attachment 33800
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33800&action=edit
example

The attached example, derived after seeing x86 Linux'es this_cpu_read_stable()
no longer getting CSE'd as expected, demonstrates the issue. 4.8.3 folded all
four read_p() invocations and each pair of read_m().

Jakub pointed out that this is an effect of the fix for PR/60663 in connection
with all x86 asm()-s getting two clobbers attached.