- Generated by
1.8.1.1
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GCC Middle and Back End API Reference
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Data Structures | |
| struct | regno_assign_info |
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inlinestatic |
Adjust cost of HARD_REGNO by INCR. Reset the cost first if it is not defined yet.
References lra_live_range::start_next.
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Assign hard registers to reload pseudos and other pseudos.
This register might have been spilled by the previous
pass. Indicate that it is no longer spilled. As non-reload pseudo assignment is changed we
should reconsider insns referring for the
pseudo. We did not assign hard regs to reload pseudos after two
iteration. It means something is wrong with asm insn
constraints. Report it. Assign an arbitrary hard register of regno class to
avoid further trouble with the asm insns. Avoid further trouble with this insn.
For asm goto, instead of fixing up all the edges
just clear the template and clear input operands
(asm goto doesn't have any output operands). This is a very rare event. We can not assign a hard
register to reload pseudo because the hard register was
assigned to another reload pseudo on a previous
assignment pass. For x86 example, on the 1st pass we
assigned CX (although another hard register could be used
for this) to reload pseudo in an insn, on the 2nd pass we
need CX (and only this) hard register for a new reload
pseudo in the same insn. FIXME: Look up the changed insns in the cached LRA insn data using
an EXECUTE_IF_SET_IN_BITMAP over changed_insns. A reload pseudo did not get a hard register on the
first iteration because of the conflict with
another reload pseudos in the same insn. So we
consider only reload pseudos assigned to hard
registers. We shall exclude inheritance pseudos as
they can occur in original insns (not reload ones).
We can omit the check for split pseudos because
they occur only in move insns containing non-reload
pseudos. We should not assign to original pseudos of inheritance
pseudos or split pseudos if any its inheritance pseudo did
not get hard register or any its split pseudo was not split
because undo inheritance/split pass will extend live range of
such inheritance or split pseudos. We change allocation for non-reload pseudo on this
iteration -- mark the pseudo for invalidation of used
alternatives of insns containing the pseudo.
References assign_hard_regno(), bitmap_clear_bit(), bitmap_ior_into(), and regno_allocno_class_array.
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Assign HARD_REGNO to REGNO.
Referenced by assign_by_spills().
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Assign temporarily HARD_REGNO to pseudo REGNO. Temporary assignment means that we might undo the data change.
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Create and set up START_POINT_RANGES.
References lra_reg::live_ranges, lra_reg_info, lra_live_range::next, not_in_chain_mark, lra_live_range::regno, lra_live_range::start, and lra_live_range::start_next.
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Try to find a free hard register for pseudo REGNO. Return the hard register on success and set *COST to the cost of using that register. (If several registers have equal cost, the one with the highest priority wins.) Return -1 on failure. If TRY_ONLY_HARD_REGNO >= 0, consider only that hard register, otherwise consider all hard registers in REGNO's class.
Remember about multi-register pseudos. For example, 2 hard
register pseudos can start on the same hard register but can
not start on HR and HR+1/HR-1. Make sure that all registers in a multi-word pseudo belong to the
required class. We can not use prohibited_class_mode_regs because it is
not defined for all classes. It needs save restore.
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Free START_POINT_RANGES.
References lra_live_max_point, max_reg_num(), and sparseset_alloc().
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Finalize data about living reload pseudos at any given program point.
References offset, and priority().
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Free the data about living pseudos at program points.
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Free REGNO_ASSIGN_INFO.
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Improve allocation by assigning the same hard regno of inheritance pseudos to the connected pseudos. We need this because inheritance pseudos are allocated after reload pseudos in the thread and when we assign a hard register to a reload pseudo we don't know yet that the connected inheritance pseudos can get the same hard register. Add pseudos with changed allocation to bitmap CHANGED_PSEUDOS.
Don't change reload pseudo allocation. It might have
this allocation for a purpose and changing it can result
in LRA cycling.
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Allocate and initialize data about living reload pseudos at any given program point.
References curr_hard_regno_costs_check.
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Allocate and initialize the data about living pseudos at program points.
References bitmap_clear_bit(), lra_live_range::finish, lra_reg_info, lra_live_range::next, reg_renumber, lra_live_range::regno, and lra_live_range::start.
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Initialize REGNO_ASSIGN_INFO and form threads.
Form the threads.
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Insert live ranges of pseudo REGNO into start chains if they are not there yet.
| bool lra_assign | ( | void | ) |
Entry function to assign hard registers to new reload pseudos starting with LRA_CONSTRAINT_NEW_REGNO_START (by possible spilling of old pseudos) and possibly to the old pseudos. The function adds what insns to process for the next constraint pass. Those are all insns who contains non-reload and non-inheritance pseudos with changed allocation. Return true if we did not spill any non-reload and non-inheritance pseudos.
Setup insns to process on the next constraint pass.
We ignore spilled pseudos created on last inheritance pass
because they will be removed. Invalidate alternatives for insn should be processed.
| void lra_setup_reg_renumber | ( | ) |
Update REG_RENUMBER and other pseudo preferences by assignment of HARD_REGNO to pseudo REGNO and print about it if PRINT_P.
We can not just reassign hard register.
References bitmap_clear(), bitmap_set_bit(), curr_pseudo_check, and overlaps_hard_reg_set_p().
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Process a pseudo copy with execution frequency COPY_FREQ connecting REGNO1 and REGNO2 to form threads.
References regno_assign_info::first, first, regno_assign_info::freq, last, and regno_assign_info::next.
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The function is used to sort *non-reload* pseudos to try to assign them hard registers. The order calculation is simpler than in the previous function and based on the pseudo frequency usage.
Prefer to assign more frequently used registers first.
If regs are equally good, sort by their numbers, so that the
results of qsort leave nothing to chance.
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Return prefix title for pseudo REGNO.
Referenced by update_hard_regno_preference().
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The function is used to sort *reload* and *inheritance* pseudos to try to assign them hard registers. We put pseudos from the same thread always nearby.
Prefer to assign reload registers with smaller classes first to
guarantee assignment to all reload registers. The code below executes rarely as nregs == 1 in most cases.
So we should not worry about using faster data structures to
check reload pseudos. Allocate bigger pseudos first to avoid register file
fragmentation. Put pseudos from the thread nearby.
If regs are equally good, sort by their numbers, so that the
results of qsort leave nothing to chance.
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The constraints pass is allowed to create equivalences between pseudos that make the current allocation "incorrect" (in the sense that pseudos are assigned to hard registers from their own conflict sets). The global variable lra_risky_transformations_p says whether this might have happened. Process pseudos assigned to hard registers (less frequently used first), spill if a conflict is found, and mark the spilled pseudos in SPILLED_PSEUDO_BITMAP. Set up LIVE_HARD_REG_PSEUDOS from pseudos, assigned to hard registers.
If it is multi-register pseudos they should start on
the same hard register.
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Set up try_hard_reg_pseudos for given program point P and class RCLASS. Those are pseudos living at P and assigned to a hard register of RCLASS. In other words, those are pseudos which can be spilled to assign a hard register of RCLASS to a pseudo living at P.
Find what pseudos could be spilled.
References bitmap_clear(), bitmap_set_bit(), lra_get_insn_regs(), lra_reg_info, lra_insn_reg::next, reg_renumber, lra_live_range::regno, lra_insn_reg::regno, and regno_allocno_class_array.
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Spill some pseudos for a reload pseudo REGNO and return hard register which should be used for pseudo after spilling. The function adds spilled pseudos to SPILLED_PSEUDO_BITMAP. When we choose hard register (and pseudos occupying the hard registers and to be spilled), we take into account not only how REGNO will benefit from the spills but also how other reload pseudos not yet assigned to hard registers benefit from the spills too. In very rare cases, the function can fail and return -1.
Invalidate try_hard_reg_pseudos elements.
Spill pseudos.
Restore the live hard reg pseudo info for spilled pseudos.
Spill:
References lra_constraint_new_regno_start, lra_live_range::regno, sparseset_set_bit(), lra_live_range::start, and lra_live_range::start_next.
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Update the preference for using HARD_REGNO for pseudos that are connected directly or indirectly with REGNO. Apply divisor DIV to any preference adjustments. The more indirectly a pseudo is connected, the smaller its effect should be. We therefore increase DIV on each "hop".
Search depth 5 seems to be enough.
References lra_reg::freq, lra_dump_file, lra_hard_reg_usage, lra_reg_info, pseudo_prefix_title(), reg_renumber, and lra_live_range::regno.
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Update the LIVE_HARD_REG_PSEUDOS and LIVE_PSEUDOS_REG_RENUMBER entries for pseudo REGNO. Assume that the register has been spilled if FREE_P, otherwise assume that it has been assigned reg_renumber[REGNO] (if >= 0). We also insert the pseudo live ranges in the start chains when it is assumed to be assigned to a hard register because we use the chains of pseudos assigned to hard registers during allocation.
References bitmap_obstack_initialize(), bitmap_set_bit(), lra_live_range::finish, lra_constraint_new_regno_start, lra_live_max_point, lra_reg_info, max_reg_num(), max_regno, lra_live_range::next, sparseset_alloc(), and lra_live_range::start.
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Bitmap finally containing all pseudos spilled on this assignment pass.
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All pseudos whose allocation was changed.
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Sparseset used to calculate reload pseudos conflicting with a given pseudo when we are trying to find a hard register for the given pseudo.
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The value used to check that cost of given hard reg is really defined currently.
Referenced by init_live_reload_and_inheritance_pseudos().
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Current pseudo check for validity of elements in TRY_HARD_REG_PSEUDOS.
Referenced by lra_setup_reg_renumber().
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Current value used for checking elements in update_hard_regno_preference_check.
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The current costs of allocation of hard regs. Defined only if the value of the corresponding element of the previous array is equal to CURR_HARD_REGNO_COSTS_CHECK.
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Array used to check that cost of the corresponding hard reg (the array element index) is really defined currently.
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Pseudos which occur in insns containing a particular pseudo.
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Map: program point -> bitmap of all pseudos living at the point and assigned to hard registers.
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reg_renumber corresponding to pseudos marked in live_hard_reg_pseudos. reg_renumber might be not matched to live_hard_reg_pseudos but live_pseudos_reg_renumber always reflects live_hard_reg_pseudos.
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Sparseset used to calculate living hard reg pseudos for some program point range.
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Sparseset used to calculate living reload/inheritance pseudos for some program point range.
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Map: program point -> bitmap of all reload and inheritance pseudos living at the point.
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All inherited, subreg or optional pseudos created before last spill sub-pass. Such pseudos are permitted to get memory instead of hard regs.
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Used as a flag that a live range is not inserted in the start point chain.
Referenced by create_live_range_start_chains().
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@verbatim
Assign reload pseudos. Copyright (C) 2010-2013 Free Software Foundation, Inc. Contributed by Vladimir Makarov vmakarov@redhat.com.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/.
This file's main objective is to assign hard registers to reload pseudos. It also tries to allocate hard registers to other pseudos, but at a lower priority than the reload pseudos. The pass does not transform the RTL. We must allocate a hard register to every reload pseudo. We try to increase the chances of finding a viable allocation by assigning the pseudos in order of fewest available hard registers first. If we still fail to find a hard register, we spill other (non-reload) pseudos in order to make room. find_hard_regno_for finds hard registers for allocation without spilling. spill_for does the same with spilling. Both functions use a cost model to determine the most profitable choice of hard and spill registers. Once we have finished allocating reload pseudos, we also try to assign registers to other (non-reload) pseudos. This is useful if hard registers were freed up by the spilling just described. We try to assign hard registers by collecting pseudos into threads. These threads contain reload and inheritance pseudos that are connected by copies (move insns). Doing this improves the chances of pseudos in the thread getting the same hard register and, as a result, of allowing some move insns to be deleted. When we assign a hard register to a pseudo, we decrease the cost of using the same hard register for pseudos that are connected by copies. If two hard registers have the same frequency-derived cost, we prefer hard registers with higher priorities. The mapping of registers to priorities is controlled by the register_priority target hook. For example, x86-64 has a few register priorities: hard registers with and without REX prefixes have different priorities. This permits us to generate smaller code as insns without REX prefixes are shorter. If a few hard registers are still equally good for the assignment, we choose the least used hard register. It is called leveling and may be profitable for some targets. Only insns with changed allocation pseudos are processed on the next constraint pass. The pseudo live-ranges are used to find conflicting pseudos. For understanding the code, it is important to keep in mind that inheritance, split, and reload pseudos created since last constraint pass have regno >= lra_constraint_new_regno_start. Inheritance and split pseudos created on any pass are in the corresponding bitmaps. Inheritance and split pseudos since the last constraint pass have also the corresponding non-negative restore_regno.
Array containing corresponding values of function lra_get_allocno_class. It is used to speed up the code.
Referenced by assign_by_spills(), and setup_try_hard_regno_pseudos().
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Map regno to the corresponding regno assignment info.
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Array used for sorting different pseudos.
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Array used for sorting reload pseudos for subsequent allocation after spilling some pseudo.
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Bitmaps used to contain spill pseudos for given pseudo hard regno and best spill pseudos for given pseudo (and best hard regno).
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Arrays of size LRA_LIVE_MAX_POINT mapping a program point to the pseudo live ranges with given start point. We insert only live ranges of pseudos interesting for assignment purposes. They are reload pseudos and pseudos assigned to hard registers.
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Pseudos who hold given hard register at the considered points.
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Array used for validity of elements in TRY_HARD_REG_PSEUDOS.
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If an element value is equal to the above variable value, then the corresponding regno has been processed for preference propagation.
1.8.1.1