On Sat, Oct 23, 2010 at 10:12 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Wed, Sep 8, 2010 at 9:43 AM, Martin Jambor <mjam...@suse.cz> wrote: >> Hi, >> >> this patch reimplements build_ref_for_offset so that it simply creates >> a MEM_REF rather than trying to figure out what combination of >> component and array refs are necessary. The main advantage of this >> approach is that this can never fail, allowing us to be more >> aggressive and remove a number of checks. >> >> There were two main problems with this, though. First is that >> MEM_REFs are not particularly readable to by users. This would be a >> problem when we are creating a reference that might be displayed to >> them in a warning or a debugger which is what we do with >> DECL_DEBUG_EXPR expressions. We sometimes construct these >> artificially when propagating accesses across assignments. So for >> those cases I retained the old implementation and only simplified it a >> bit - it is now called build_user_friendly_ref_for_offset. >> >> The other problem was bit-fields. Constructing accesses to them was >> difficult enough but then I realized that I was not even able to >> detect the cases when I was accessing a bit field if their offset >> happened to be on a byte boundary. I thought I would be able to >> figure this out from TYPE_SIZE and TYPE_PRECISION of exp_type but >> combinations that signal a bit-field in one language may not be >> applied in another (in C, small TYPE_PRECISION denotes bit-fields and >> TYPE_SIZE is big, but for example Fortran booleans have the precision >> set to one even though they are not bit-fields). >> >> So in the end I based the detection on the access structures that >> represented the thing being loaded or stored which I knew had their >> sizes correct because they are based on field sizes. Since I use the >> access, the simplest way to actually create the reference to the bit >> field is to re-use the last component ref of its expression - that is >> what build_ref_for_model (meaning a model access) does. Separating >> this from build_ref_for_offset (which cannot handle bit-fields) makes >> the code a bit cleaner and keeps the latter function for other users >> which know nothing about SRA access structures. >> >> I hope that you'll find these approaches reasonable. The patch was >> bootstrapped and tested on x86_64-linux without any issues. I'd like >> to commit it to trunk but I'm sure there will be comments and >> suggestions. >> >> Thanks, >> >> Martin >> >> >> >> 2010-09-08 Martin Jambor <mjam...@suse.cz> >> >> PR tree-optimization/44972 >> * tree-sra.c: Include toplev.h. >> (build_ref_for_offset): Entirely reimplemented. >> (build_ref_for_model): New function. >> (build_user_friendly_ref_for_offset): New function. >> (analyze_access_subtree): Removed build_ref_for_offset check. >> (propagate_subaccesses_across_link): Likewise. >> (create_artificial_child_access): Use >> build_user_friendly_ref_for_offset. >> (propagate_subaccesses_across_link): Likewise. >> (ref_expr_for_all_replacements_p): Removed. >> (generate_subtree_copies): Updated comment. Use build_ref_for_model. >> (sra_modify_expr): Use build_ref_for_model. >> (load_assign_lhs_subreplacements): Likewise. >> (sra_modify_assign): Removed ref_expr_for_all_replacements_p checks, >> checks for return values of build_ref_for_offset. >> * ipa-cp.c (ipcp_lattice_from_jfunc): No need to check return value of >> build_ref_for_offset. >> * ipa-prop.h: Include gimple.h >> * ipa-prop.c (ipa_compute_jump_functions): Update to look for >> MEM_REFs. >> (ipa_analyze_indirect_call_uses): Update comment. >> * Makefile.in (tree-sra.o): Add $(GIMPLE_H) to dependencies. >> (IPA_PROP_H): Likewise. > > This caused: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46150 >
This also caused: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49039 -- H.J.
