https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70189
Bug ID: 70189
Summary: Combine constant-pool logic from gimplify + SRA
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: alalaw01 at gcc dot gnu.org
Target Milestone: ---
Following PR/63679 (r232506), gimplify.c (gimplify_init_constructor) uses lots
of heuristics to choose between pushing initializers out to the constant pool
(by calling tree_output_constant_def) or outputting many elementwise
statements. Then, in tree-sra.c (analyze_all_variable_accesses), we use more
heuristics to decide which constant-pool loads to completely_scalarize,
turning those back into elementwise statements. (These get pulled back in from
the constant pool and the constant-pool entry deleted.) Both of these sets of
heuristics are platform dependent (gimplify.c uses can_move_by_pieces,
CLEAR_RATIO; tree-sra.c uses get_move_ratio).
Instead we should put all this logic in one place; this would make it clearer,
and we'd probably get better overall decisions. The suggestion is for
gimplify.c to always push out to the constant pool, as this makes initial tree
the same on all platforms, and for all the logic/heuristics to go into SRA (as,
being later, we then have more information available to maybe make better
decisions in the future).
