On Mon, 27 Feb 2023 23:02:15 GMT, Phil Race <p...@openjdk.org> wrote:
>> Jayathirth D V has updated the pull request incrementally with one >> additional commit since the last revision: >> >> Update comment > > make/modules/java.desktop/lib/Awt2dLibraries.gmk line 130: > >> 128: BUILD_LIBAWT_debug_mem.c_CFLAGS := -w >> 129: # This option improves performance of FillRect/FillOval in Java2D by >> 15% for some gcc >> 130: LIBAWT_CFLAGS += -fpic > > So .. acc. to the eval in JBS we can get rid of -fgcse-after-reload because > it is implied by -O3 > And Erik says -fPIC is implied by -fpic > > So how is -fpic different than -fPIC in a way that helps here ? > So far as I can tell the -fpic are using just limits the size of the global > offset table that -fPIC will generate. > Since we had an unlimited offset table before, then -fpic won't change > anything. > So what's the explanation ? Thanks @prrace for your inputs. I dont think -fPIC is implied by -fpic. @erikj79 please clarify. Difference between -fpic and -fPIC: 1) With -fPIC we have unlimited storage capacity for global offset table and with -fpic on some platforms we have limitation on this size. For aarch64 it is 28k, but in case of x86 size of GOT is unlimited irrespective of -fPIC or -fpic. This is already captured. 2) Also it looks like if we use -fpic option instead of -fPIC we may generate smaller/faster code as mentioned at http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html. Looks like in our case, 28k GOT size suffices and we are able to create smaller/faster code for libawt in case of aarch64. This inturn looks to be related to usage of -msmall-data or -mlarge-data flags. -fpic implies -msmall-data and -fPIC implies -mlarge-data while generating code for shared libraries. -msmall-data also talks about data being nearer and easily accessible compared to -mlarge-data(https://man7.org/linux/man-pages/man1/gcc.1.html) Also i can make this change specific to aarch64 since we are seeing its effect only on aarch64. ------------- PR: https://git.openjdk.org/jdk/pull/12761
