From patchwork Fri Jul 9 15:04:26 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [fortran] PR4773 - [4.6 Regression] Unnecessary temporaries increase the runtime for channel.f90 by ~70% Date: Fri, 09 Jul 2010 05:04:26 -0000 From: Paul Richard Thomas X-Patchwork-Id: 58408 Message-Id: To: fortran@gcc.gnu.org, gcc-patches Revision 161670 affected an optimization used for array_lhs = array_valued_function (args...). In order to prevent aliasing with the result, which is passed by reference, a fairly conservative test was applied to generate a temporary, if needed. Unfortunately, this reduced the performance of gfortran with some code; most notably with channel.f90. This patch tests if the 'array_lhs' has ever been host associated, on condition that 'array_valued_function' is contained, in addition to checking that the result is not use-associated, a pointer or a target. If this is not the case, no temporary is generated. Clearly some further optimization would be possible, if the 'array_lhs' were specifically not host associated to 'array_valued_function' OR ANY OF IT'S CALLEEs. This latter condition is rather difficult to implement, which is why I have not even tried it. Bootstrapped and regtested on RHEL5.3/i686 - OK for trunk and.....? Cheers Paul 2010-07-09 Paul Thomas PR fortran/44773 * trans-expr.c (arrayfunc_assign_needs_temporary): No temporary if the lhs has never been host associated, as well as not being use associated, a pointer or a target. * resolve.c (resolve_variable): Mark variables that are host associated. * gfortran.h: Add the host_assoc bit to the symbol_attribute structure. Index: gcc/fortran/trans-expr.c =================================================================== --- gcc/fortran/trans-expr.c (revision 161983) +++ gcc/fortran/trans-expr.c (working copy) @@ -4978,6 +4978,11 @@ if (!expr2->value.function.esym->attr.contained) return false; + /* A temporary is not needed if the lhs has never been host + associated and the procedure is contained. */ + else if (!sym->attr.host_assoc) + return false; + /* A temporary is not needed if the variable is local and not a pointer, a target or a result. */ if (sym->ns->parent Index: gcc/fortran/gfortran.h =================================================================== --- gcc/fortran/gfortran.h (revision 161983) +++ gcc/fortran/gfortran.h (working copy) @@ -682,7 +682,8 @@ use_assoc:1, /* Symbol has been use-associated. */ use_only:1, /* Symbol has been use-associated, with ONLY. */ use_rename:1, /* Symbol has been use-associated and renamed. */ - imported:1; /* Symbol has been associated by IMPORT. */ + imported:1, /* Symbol has been associated by IMPORT. */ + host_assoc:1; /* Symbol has been host associated. */ unsigned in_namelist:1, in_common:1, in_equivalence:1; unsigned function:1, subroutine:1, procedure:1; Index: gcc/fortran/resolve.c =================================================================== --- gcc/fortran/resolve.c (revision 161983) +++ gcc/fortran/resolve.c (working copy) @@ -4772,6 +4772,15 @@ sym->entry_id = current_entry_id + 1; } + /* If a symbol has been host_associated mark it. This is used latter, + to identify if aliasing is possible via host association. */ + if (sym->attr.flavor == FL_VARIABLE + && gfc_current_ns->parent + && (gfc_current_ns->parent == sym->ns + || (gfc_current_ns->parent->parent + && gfc_current_ns->parent->parent == sym->ns))) + sym->attr.host_assoc = 1; + resolve_procedure: if (t == SUCCESS && resolve_procedure_expression (e) == FAILURE) t = FAILURE;