The Linux kernel dynamically patches in __fentry__ calls in and
out at runtime. This allows using function tracing for debugging
in production kernels without (significant) performance penalty.
For this it needs a table pointing to each __fentry__ call.
The way it is currently implemented is that a special
perl script scans the object file, generates the table in a special
section. When the kernel boots up it nops the calls, and
then later patches in the calls again as needed.
The recordmcount.pl script in the kernel works, but it seems
cleaner and faster to support the code generation of the patch table
directly in gcc.
This also allows to nop the calls directly at code generation
time, which allows to skip a patching step at kernel boot.
I also expect that a patchable production tracing facility is also useful
for other applications.
For example it could be used in ftracer
(https://github.com/andikleen/ftracer)
Having a nop area at the beginning of each function can be also
also useful for other things. For example it can be used to patch
functions at runtime to point to different functions, to do
binary updates without restarting the program (like ksplice or
similar)
This patch implements two new options for the i386 target:
-mrecord-mcount
Generate a __mcount_loc section entry for each __fentry__ or mcount
call. The section is compatible with the kernel convention
and the data is put into a section loaded at runtime.
-mnop-mcount
Generate the mcount/__fentry__ call as 5 byte nop that can be
patched in later. The nop is generated as a single instruction,
as the Linux kernel run time patching relies on this.
Limitations:
- I didn't implement -mnop-mcount for -fPIC. This
would need a good single instruction 6 byte NOP and it seems a
bit pointless, as the patching would prevent text sharing.
- I didn't implement noping for targets that pass a variable
to mcount.
- The facility could be useful on architectures too. Currently
the mcount code is target specific, so I made it a i386 option.
gcc/:
2014-09-25 Andi Kleen <ak@linux.intel.com>
* config/i386/i386.c (x86_print_call_or_nop): New function.
(x86_function_profiler): Support -mnop-mcount and
-mrecord-mcount.
* config/i386/i386.opt (-mnop-mcount, -mrecord-mcount): Add
* doc/invoke.texi: Document -mnop-mcount, -mrecord-mcount.
gcc/testsuite:
2014-09-25 Andi Kleen <ak@linux.intel.com>
* gcc.target/i386/nop-mcount.c: New file.
* gcc.target/i386/record-mcount.c: New file.
From-SVN: r215629
* ipa-devirt.c (polymorphic_call_target_d): Add SPECULATIVE; reorder
for better storage.
(polymorphic_call_target_hasher::hash): Hash SPECULATIVE.
(possible_polymorphic_call_targets): Instead of computing both
speculative and non-speculative answers, do just one at a time.
Replace NONSPECULATIVE_TARGETSP parameter with SPECULATIVE flag.
(dump_targets): Break out from ...
(dump_possible_polymorphic_call_targets): ... here; dump both speculative
and non-speculative lists.
(ipa_devirt): Update for new possible_polymorphic_call_targets API.
* ipa-utils.h (possible_polymorphic_call_targets): Update.
* testsuite/g++.dg/ipa/devirt-34.C: Update template.
From-SVN: r215614
gcc/
* shrink-wrap.c (move_insn_for_shrink_wrap): Initialize the live-in of new
created BB as the intersection of live-in from "old_dest" and live-out from
"bb".
gcc/testsuite/
* gcc.target/i386/shrink_wrap_1.c: New test.
From-SVN: r215611
[gcc]
2014-09-25 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
PR target/63335
* config/rs6000/rs6000-c.c (altivec_build_resolved_builtin):
Exclude VSX_BUILTIN_XVCMPGEDP_P from special handling.
[gcc/testsuite]
2014-09-25 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
PR target/63335
* gcc.target/powerpc/pr63335.c: New test.
From-SVN: r215599
PR tree-optimization/63341
* tree-vectorizer.h (vect_create_data_ref_ptr,
vect_create_addr_base_for_vector_ref): Add another tree argument
defaulting to NULL_TREE.
* tree-vect-data-refs.c (vect_create_data_ref_ptr): Add byte_offset
argument, pass it down to vect_create_addr_base_for_vector_ref.
(vect_create_addr_base_for_vector_ref): Add byte_offset argument,
add that to base_offset too if non-NULL.
* tree-vect-stmts.c (vectorizable_load): Add byte_offset variable,
for dr_explicit_realign_optimized set it to vector byte size
- 1 instead of setting offset, pass byte_offset down to
vect_create_data_ref_ptr.
* gcc.dg/vect/pr63341-1.c: New test.
* gcc.dg/vect/pr63341-2.c: New test.
From-SVN: r215583
2014-09-25 Andreas Arnez <arnez@linux.vnet.ibm.com>
PR 63300/debug
* tree.c (check_base_type): New.
(check_qualified_type): Exploit new helper function above.
* tree.h (check_base_type): New prototype.
* dwarf2out.c (get_nearest_type_subqualifiers): New.
(modified_type_die): Fix handling for qualifiers. Qualifiers to
"peel off" are now determined using get_nearest_type_subqualifiers.
2014-09-25 Mark Wielaard <mjw@redhat.com>
PR 63300/debug
* gcc.dg/debug/dwarf2/stacked-qualified-types-1.c: New testcase.
* gcc.dg/debug/dwarf2/stacked-qualified-types-2.c: Likewise.
* gcc.dg/guality/pr63300-const-volatile.c: New testcase.
From-SVN: r215582
* cgraph.h (class ipa_polymorphic_call_context): Move here from
ipa-utils.h; add stream_int and stream_out methods.
(cgraph_indirect_call_info): Remove SPECILATIVE_OFFSET,
OUTER_TYPE, SPECULATIVE_OUTER_TYPE, MAYBE_IN_CONSTRUCTION
MAYBE_DERIVED_TYPE and SPECULATIEVE_MAYBE_DERIVED_TYPE;
add CONTEXT.
(ipa_polymorphic_call_context::ipa_polymorphic_call_context,
ipa_polymorphic_call_context::ipa_polymorphic_call_context,
ipa_polymorphic_call_context::clear_speculation,
ipa_polymorphic_call_context::clear_outer_type): Move here from
ipa-utils.h
* ipa-utils.h (class ipa_polymorphic_call_context): Move to cgraph.h
(ipa_polymorphic_call_context::ipa_polymorphic_call_context,
ipa_polymorphic_call_context::ipa_polymorphic_call_context,
ipa_polymorphic_call_context::clear_speculation,
ipa_polymorphic_call_context::clear_outer_type): Likewise.
* ipa-devirt.c: Include data-streamer.h, lto-streamer.h and
streamer-hooks.h
(ipa_polymorphic_call_context::stream_out): New method.
(ipa_polymorphic_call_context::stream_in): New method.
(noncall_stmt_may_be_vtbl_ptr_store): Add forgotten static.
* ipa-prop.c (ipa_analyze_indirect_call_uses): Do not care about
OUTER_TYPE.
(ipa_analyze_call_uses): Simplify.
(update_indirect_edges_after_inlining): Do not care about outer_type.
(ipa_write_indirect_edge_info): Update.
(ipa_write_indirect_edge_info): Likewise.
* cgraph.c (cgraph_node::create_indirect_edge): Simplify.
(dump_edge_flags): Break out from ...
(cgraph_node::dump): ... here; dump indirect edges.
From-SVN: r215575
* ipa-utils.h (polymorphic_call_context): Add
metdhos dump, debug and clear_outer_type.
(ipa_polymorphic_call_context::ipa_polymorphic_call_context): Simplify.
(ipa_polymorphic_call_context::clear_outer_type): New method.
* ipa-prop.c (ipa_analyze_call_uses): Do not overwrite offset.
* ipa-devirt.c (types_odr_comparable): New function.
(types_must_be_same_for_odr): New function.
(odr_subtypes_equivalent_p): Simplify.
(possible_placement_new): Break out from ...
(ipa_polymorphic_call_context::restrict_to_inner_type): ... here;
be more cuatious about returning false in cases the context may be
valid in derived type or via placement new.
(contains_type_p): Clear maybe_derived_type
(ipa_polymorphic_call_context::dump): New method.
(ipa_polymorphic_call_context::debug): New method.
(ipa_polymorphic_call_context::set_by_decl): Cleanup comment.
(ipa_polymorphic_call_context::set_by_invariant): Simplify.
(ipa_polymorphic_call_context::ipa_polymorphic_call_context): Simplify.
(possible_polymorphic_call_targets): Trust context.restrict_to_inner_class
to suceed on all valid cases; remove confused sanity check.
(dump_possible_polymorphic_call_targets): Simplify.
From-SVN: r215569
[gcc]
2014-09-24 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
* config/rs6000/rs6000.c (insn_is_swappable_p): Don't provide
special handling for stores whose SET_SRC is an UNSPEC (such as
UNSPEC_STVE).
[gcc/testsuite]
2014-09-24 Bill Schmidt <wschmidt@linux.vnet.ibm.com>
* gcc.target/powerpc/swaps-p8-17.c: New test.
From-SVN: r215564
gcc/
* shrink-wrap.c (move_insn_for_shrink_wrap): Add further check when
!REG_P (src) to release more instruction sink opportunities.
gcc/testsuite/
* gcc.target/aarch64/shrink_wrap_symbol_ref_1.c: New testcase.
From-SVN: r215563
2014-09-24 Martin Jambor <mjambor@suse.cz>
* ipa-prop.c (ipa_edge_duplication_hook): Update controlled_use_count
when duplicating a PASS_THROUGH jump function when creating a
speculative edge.
From-SVN: r215560
2014-09-24 Thomas Preud'homme <thomas.preudhomme@arm.com>
gcc/
PR tree-optimization/63266
* tree-ssa-math-opts.c (struct symbolic_number): Add comment about
marker for unknown byte value.
(MARKER_MASK): New macro.
(MARKER_BYTE_UNKNOWN): New macro.
(HEAD_MARKER): New macro.
(do_shift_rotate): Mark bytes with unknown values due to sign
extension when doing an arithmetic right shift. Replace hardcoded
mask for marker by new MARKER_MASK macro.
(find_bswap_or_nop_1): Likewise and adjust ORing of two symbolic
numbers accordingly.
gcc/testsuite/
PR tree-optimization/63266
* gcc.dg/optimize-bswapsi-1.c (swap32_d): New bswap pass test.
From-SVN: r215546
