php is slower with lto build workaround

[justanerd]

gcc version 7.3.0 (Gentoo 7.3.0 p1.0)

I've been playing around with my build flags.
I noticed a regression when --disable-gcc-global-regs is enabled.
Building php without LTO and without --disable-gcc-global-regs results in faster php here are the php bench results:

with lto and workaround

                   test_arithmetic         0.0012 seconds.
              test_array_operators         0.0007 seconds.
                      test_bitwise         0.0007 seconds.
                      test_casting         0.1642 seconds.
                    test_chr_fixed         0.0473 seconds.
                test_chr_hardcoded         0.0470 seconds.
                      test_chr_var         0.0830 seconds.
                 test_comment_loop         0.0206 seconds.
                      test_compare         0.0007 seconds.
                test_compare_false         0.0007 seconds.
               test_compare_invert         0.0008 seconds.
               test_compare_strict         0.0007 seconds.
             test_compare_unstrict         0.0008 seconds.
                    test_constants         0.0080 seconds.
                        test_crc32         0.0052 seconds.
                     test_do_while         0.0642 seconds.
               test_do_while_break         0.0069 seconds.
                        test_empty         0.0007 seconds.
                   test_empty_loop         0.0207 seconds.
                         test_ereg         0.0148 seconds.
                      test_foreach         0.0996 seconds.
                    test_get_class         0.0046 seconds.
         test_global_scalar_assign         0.0135 seconds.
         test_global_string_assign         0.0303 seconds.
                  test_if_constant         0.0007 seconds.
                    test_increment         0.0041 seconds.
                     test_is_array         0.0008 seconds.
                    test_is_object         0.0007 seconds.
                      test_is_type         0.0007 seconds.
                        test_isset         0.0007 seconds.
                         test_line         0.0007 seconds.
           test_local_array_assign         0.0020 seconds.
         test_local_boolean_assign         0.0007 seconds.
           test_local_float_assign         0.0007 seconds.
            test_local_hash_assign         0.0057 seconds.
         test_local_integer_assign         0.0008 seconds.
          test_local_object_assign         0.0069 seconds.
          test_local_scalar_assign         0.0008 seconds.
          test_local_string_assign         0.0007 seconds.
                          test_md5         0.0189 seconds.
                    test_microtime         0.0493 seconds.
                      test_mt_rand         0.0038 seconds.
                          test_ord         0.1215 seconds.
            test_ordered_functions         0.1278 seconds.
 test_ordered_functions_references         0.1844 seconds.
                   test_preg_match         0.0118 seconds.
                         test_rand         0.0038 seconds.
                   test_references         0.0024 seconds.
                         test_sha1         0.0220 seconds.
                test_string_append         0.0007 seconds.
                       test_strlen         0.0007 seconds.
                       test_switch         0.0382 seconds.
                         test_time         0.0031 seconds.
          test_unordered_functions         0.1268 seconds.
           test_variable_variables         0.0080 seconds.
                        test_while         0.0645 seconds.

System     : Linux deepspace 4.16.0-jk1 #1 SMP PREEMPT Fri Apr 27 12:43:08 CEST 2018 x86_64
PHP version: 7.2.5
PHPBench   : 0.8.1
Date       : April 27, 2018, 7:12 pm
Tests      : 56
Iterations : 100000
Total time : 1 seconds
Score      : 688687 (higher is better)

without lto and workaround

                   test_arithmetic         0.0009 seconds.
              test_array_operators         0.0006 seconds.
                      test_bitwise         0.0006 seconds.
                      test_casting         0.1619 seconds.
                    test_chr_fixed         0.0418 seconds.
                test_chr_hardcoded         0.0405 seconds.
                      test_chr_var         0.0685 seconds.
                 test_comment_loop         0.0173 seconds.
                      test_compare         0.0006 seconds.
                test_compare_false         0.0006 seconds.
               test_compare_invert         0.0006 seconds.
               test_compare_strict         0.0006 seconds.
             test_compare_unstrict         0.0006 seconds.
                    test_constants         0.0074 seconds.
                        test_crc32         0.0049 seconds.
                     test_do_while         0.0426 seconds.
               test_do_while_break         0.0058 seconds.
                        test_empty         0.0006 seconds.
                   test_empty_loop         0.0171 seconds.
                         test_ereg         0.0144 seconds.
                      test_foreach         0.0592 seconds.
                    test_get_class         0.0040 seconds.
         test_global_scalar_assign         0.0133 seconds.
         test_global_string_assign         0.0284 seconds.
                  test_if_constant         0.0006 seconds.
                    test_increment         0.0034 seconds.
                     test_is_array         0.0006 seconds.
                    test_is_object         0.0006 seconds.
                      test_is_type         0.0006 seconds.
                        test_isset         0.0006 seconds.
                         test_line         0.0006 seconds.
           test_local_array_assign         0.0017 seconds.
         test_local_boolean_assign         0.0006 seconds.
           test_local_float_assign         0.0006 seconds.
            test_local_hash_assign         0.0050 seconds.
         test_local_integer_assign         0.0006 seconds.
          test_local_object_assign         0.0058 seconds.
          test_local_scalar_assign         0.0006 seconds.
          test_local_string_assign         0.0006 seconds.
                          test_md5         0.0190 seconds.
                    test_microtime         0.0494 seconds.
                      test_mt_rand         0.0033 seconds.
                          test_ord         0.0887 seconds.
            test_ordered_functions         0.0840 seconds.
 test_ordered_functions_references         0.1574 seconds.
                   test_preg_match         0.0109 seconds.
                         test_rand         0.0033 seconds.
                   test_references         0.0021 seconds.
                         test_sha1         0.0205 seconds.
                test_string_append         0.0006 seconds.
                       test_strlen         0.0006 seconds.
                       test_switch         0.0316 seconds.
                         test_time         0.0025 seconds.
          test_unordered_functions         0.0822 seconds.
           test_variable_variables         0.0065 seconds.
                        test_while         0.0420 seconds.

System     : Linux deepspace 4.16.0-jk1 #1 SMP PREEMPT Fri Apr 27 12:43:08 CEST 2018 x86_64
PHP version: 7.2.5
PHPBench   : 0.8.1
Date       : April 27, 2018, 7:16 pm
Tests      : 56
Iterations : 100000
Total time : 1 seconds
Score      : 862077 (higher is better)

[InBetweenNames]

Interesting! Is your non-LTO build -O3 ?

[justanerd]

Both with -O3

[InBetweenNames]

It seems to me that the benefits of gcc-global-regs outweigh the benefits of LTO, according to these benchmarks. What do you think about leaving the PHP entry in ltoworkarounds.conf for documentation, but commented out?

[justanerd]

Thats fine, I did the same thing locally for testing.