[Bug lto/68384] New: LTO error for global register variables in PHP 7 compiling on powerpc64le

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68384

            Bug ID: 68384
           Summary: LTO error for global register variables in PHP 7
                    compiling on powerpc64le
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: acsawdey at gcc dot gnu.org
  Target Milestone: ---

Created attachment 36734
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36734&action=edit
zend.i from reduced test case

If you attempt to build PHP 7 with -flto, you encounter errors for the 2
register global variables it uses:

zend_execute.i:81:32: error: global register variable follows a function
definition
        register const zend_op *opline __asm__("r29");
                                ^

zend_execute.i:80:36: error: global register variable follows a function
definition
        register zend_execute_data *execute_data __asm__("r28");
                                    ^

I've reduced this with multidelta and the preprocessed files are attached.

Reproduce with:

gcc -flto -O3 main.i php_cli.i zend_execute.i zend.i

Of course this test case won't link or do anything useful, but it hits the LTO
issue before getting to the link phase.

I did my testing with trunk 230270, but older gcc 4.8.x also has the same
problem.