/* Natural loop functions Copyright (C) 1987-2020 Free Software Foundation, Inc. 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 . */ #ifndef GCC_CFGLOOP_H #define GCC_CFGLOOP_H #include "cfgloopmanip.h" /* Structure to hold decision about unrolling/peeling. */ enum lpt_dec { LPT_NONE, LPT_UNROLL_CONSTANT, LPT_UNROLL_RUNTIME, LPT_UNROLL_STUPID }; struct GTY (()) lpt_decision { enum lpt_dec decision; unsigned times; }; /* The type of extend applied to an IV. */ enum iv_extend_code { IV_SIGN_EXTEND, IV_ZERO_EXTEND, IV_UNKNOWN_EXTEND }; /* The structure describing a bound on number of iterations of a loop. */ class GTY ((chain_next ("%h.next"))) nb_iter_bound { public: /* The statement STMT is executed at most ... */ gimple *stmt; /* ... BOUND + 1 times (BOUND must be an unsigned constant). The + 1 is added for the following reasons: a) 0 would otherwise be unused, while we would need to care more about overflows (as MAX + 1 is sometimes produced as the estimate on number of executions of STMT). b) it is consistent with the result of number_of_iterations_exit. */ widest_int bound; /* True if the statement will cause the loop to be leaved the (at most) BOUND + 1-st time it is executed, that is, all the statements after it are executed at most BOUND times. */ bool is_exit; /* The next bound in the list. */ class nb_iter_bound *next; }; /* Description of the loop exit. */ struct GTY ((for_user)) loop_exit { /* The exit edge. */ edge e; /* Previous and next exit in the list of the exits of the loop. */ struct loop_exit *prev; struct loop_exit *next; /* Next element in the list of loops from that E exits. */ struct loop_exit *next_e; }; struct loop_exit_hasher : ggc_ptr_hash { typedef edge compare_type; static hashval_t hash (loop_exit *); static bool equal (loop_exit *, edge); static void remove (loop_exit *); }; typedef class loop *loop_p; /* An integer estimation of the number of iterations. Estimate_state describes what is the state of the estimation. */ enum loop_estimation { /* Estimate was not computed yet. */ EST_NOT_COMPUTED, /* Estimate is ready. */ EST_AVAILABLE, EST_LAST }; /* The structure describing non-overflow control induction variable for loop's exit edge. */ struct GTY ((chain_next ("%h.next"))) control_iv { tree base; tree step; struct control_iv *next; }; /* Structure to hold information for each natural loop. */ class GTY ((chain_next ("%h.next"))) loop { public: /* Index into loops array. Note indices will never be reused after loop is destroyed. */ int num; /* Number of loop insns. */ unsigned ninsns; /* Basic block of loop header. */ basic_block header; /* Basic block of loop latch. */ basic_block latch; /* For loop unrolling/peeling decision. */ struct lpt_decision lpt_decision; /* Average number of executed insns per iteration. */ unsigned av_ninsns; /* Number of blocks contained within the loop. */ unsigned num_nodes; /* Superloops of the loop, starting with the outermost loop. */ vec *superloops; /* The first inner (child) loop or NULL if innermost loop. */ class loop *inner; /* Link to the next (sibling) loop. */ class loop *next; /* Auxiliary info specific to a pass. */ PTR GTY ((skip (""))) aux; /* The number of times the latch of the loop is executed. This can be an INTEGER_CST, or a symbolic expression representing the number of iterations like "N - 1", or a COND_EXPR containing the runtime conditions under which the number of iterations is non zero. Don't access this field directly: number_of_latch_executions computes and caches the computed information in this field. */ tree nb_iterations; /* An integer guaranteed to be greater or equal to nb_iterations. Only valid if any_upper_bound is true. */ widest_int nb_iterations_upper_bound; widest_int nb_iterations_likely_upper_bound; /* An integer giving an estimate on nb_iterations. Unlike nb_iterations_upper_bound, there is no guarantee that it is at least nb_iterations. */ widest_int nb_iterations_estimate; /* If > 0, an integer, where the user asserted that for any I in [ 0, nb_iterations ) and for any J in [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations of the loop can be safely evaluated concurrently. */ int safelen; /* Preferred vectorization factor for the loop if non-zero. */ int simdlen; /* Constraints are generally set by consumers and affect certain semantics of niter analyzer APIs. Currently the APIs affected are number_of_iterations_exit* functions and their callers. One typical use case of constraints is to vectorize possibly infinite loop: 1) Compute niter->assumptions by calling niter analyzer API and record it as possible condition for loop versioning. 2) Clear buffered result of niter/scev analyzer. 3) Set constraint LOOP_C_FINITE assuming the loop is finite. 4) Analyze data references. Since data reference analysis depends on niter/scev analyzer, the point is that niter/scev analysis is done under circumstance of LOOP_C_FINITE constraint. 5) Version the loop with niter->assumptions computed in step 1). 6) Vectorize the versioned loop in which niter->assumptions is checked to be true. 7) Update constraints in versioned loops so that niter analyzer in following passes can use it. Note consumers are usually the loop optimizers and it is consumers' responsibility to set/clear constraints correctly. Failing to do that might result in hard to track down bugs in niter/scev consumers. */ unsigned constraints; /* An integer estimation of the number of iterations. Estimate_state describes what is the state of the estimation. */ ENUM_BITFIELD(loop_estimation) estimate_state : 8; unsigned any_upper_bound : 1; unsigned any_estimate : 1; unsigned any_likely_upper_bound : 1; /* True if the loop can be parallel. */ unsigned can_be_parallel : 1; /* True if -Waggressive-loop-optimizations warned about this loop already. */ unsigned warned_aggressive_loop_optimizations : 1; /* True if this loop should never be vectorized. */ unsigned dont_vectorize : 1; /* True if we should try harder to vectorize this loop. */ unsigned force_vectorize : 1; /* True if the loop is part of an oacc kernels region. */ unsigned in_oacc_kernels_region : 1; /* True if the loop is known to be finite. This is a localized flag_finite_loops or similar pragmas state. */ unsigned finite_p : 1; /* The number of times to unroll the loop. 0 means no information given, just do what we always do. A value of 1 means do not unroll the loop. A value of USHRT_MAX means unroll with no specific unrolling factor. Other values means unroll with the given unrolling factor. */ unsigned short unroll; /* If this loop was inlined the main clique of the callee which does not need remapping when copying the loop body. */ unsigned short owned_clique; /* For SIMD loops, this is a unique identifier of the loop, referenced by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE builtins. */ tree simduid; /* In loop optimization, it's common to generate loops from the original loop. This field records the index of the original loop which can be used to track the original loop from newly generated loops. This can be done by calling function get_loop (cfun, orig_loop_num). Note the original loop could be destroyed for various reasons thus no longer exists, as a result, function call to get_loop returns NULL pointer. In this case, this field should not be used and needs to be cleared whenever possible. */ int orig_loop_num; /* Upper bound on number of iterations of a loop. */ class nb_iter_bound *bounds; /* Non-overflow control ivs of a loop. */ struct control_iv *control_ivs; /* Head of the cyclic list of the exits of the loop. */ struct loop_exit *exits; /* Number of iteration analysis data for RTL. */ class niter_desc *simple_loop_desc; /* For sanity checking during loop fixup we record here the former loop header for loops marked for removal. Note that this prevents the basic-block from being collected but its index can still be reused. */ basic_block former_header; }; /* Set if the loop is known to be infinite. */ #define LOOP_C_INFINITE (1 << 0) /* Set if the loop is known to be finite without any assumptions. */ #define LOOP_C_FINITE (1 << 1) /* Set C to the LOOP constraint. */ static inline void loop_constraint_set (class loop *loop, unsigned c) { loop->constraints |= c; } /* Clear C from the LOOP constraint. */ static inline void loop_constraint_clear (class loop *loop, unsigned c) { loop->constraints &= ~c; } /* Check if C is set in the LOOP constraint. */ static inline bool loop_constraint_set_p (class loop *loop, unsigned c) { return (loop->constraints & c) == c; } /* Flags for state of loop structure. */ enum { LOOPS_HAVE_PREHEADERS = 1, LOOPS_HAVE_SIMPLE_LATCHES = 2, LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4, LOOPS_HAVE_RECORDED_EXITS = 8, LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16, LOOP_CLOSED_SSA = 32, LOOPS_NEED_FIXUP = 64, LOOPS_HAVE_FALLTHRU_PREHEADERS = 128 }; #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \ | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS) #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES) /* Structure to hold CFG information about natural loops within a function. */ struct GTY (()) loops { /* State of loops. */ int state; /* Array of the loops. */ vec *larray; /* Maps edges to the list of their descriptions as loop exits. Edges whose sources or destinations have loop_father == NULL (which may happen during the cfg manipulations) should not appear in EXITS. */ hash_table *GTY(()) exits; /* Pointer to root of loop hierarchy tree. */ class loop *tree_root; }; /* Loop recognition. */ bool bb_loop_header_p (basic_block); void init_loops_structure (struct function *, struct loops *, unsigned); extern struct loops *flow_loops_find (struct loops *); extern void disambiguate_loops_with_multiple_latches (void); extern void flow_loops_free (struct loops *); extern void flow_loops_dump (FILE *, void (*)(const class loop *, FILE *, int), int); extern void flow_loop_dump (const class loop *, FILE *, void (*)(const class loop *, FILE *, int), int); class loop *alloc_loop (void); extern void flow_loop_free (class loop *); int flow_loop_nodes_find (basic_block, class loop *); unsigned fix_loop_structure (bitmap changed_bbs); bool mark_irreducible_loops (void); void release_recorded_exits (function *); void record_loop_exits (void); void rescan_loop_exit (edge, bool, bool); void sort_sibling_loops (function *); /* Loop data structure manipulation/querying. */ extern void flow_loop_tree_node_add (class loop *, class loop *, class loop * = NULL); extern void flow_loop_tree_node_remove (class loop *); extern bool flow_loop_nested_p (const class loop *, const class loop *); extern bool flow_bb_inside_loop_p (const class loop *, const_basic_block); extern class loop * find_common_loop (class loop *, class loop *); class loop *superloop_at_depth (class loop *, unsigned); struct eni_weights; extern int num_loop_insns (const class loop *); extern int average_num_loop_insns (const class loop *); extern unsigned get_loop_level (const class loop *); extern bool loop_exit_edge_p (const class loop *, const_edge); extern bool loop_exits_to_bb_p (class loop *, basic_block); extern bool loop_exits_from_bb_p (class loop *, basic_block); extern void mark_loop_exit_edges (void); extern dump_user_location_t get_loop_location (class loop *loop); /* Loops & cfg manipulation. */ extern basic_block *get_loop_body (const class loop *); extern unsigned get_loop_body_with_size (const class loop *, basic_block *, unsigned); extern basic_block *get_loop_body_in_dom_order (const class loop *); extern basic_block *get_loop_body_in_bfs_order (const class loop *); extern basic_block *get_loop_body_in_custom_order (const class loop *, int (*) (const void *, const void *)); extern basic_block *get_loop_body_in_custom_order (const class loop *, void *, int (*) (const void *, const void *, void *)); extern vec get_loop_exit_edges (const class loop *, basic_block * = NULL); extern edge single_exit (const class loop *); extern edge single_likely_exit (class loop *loop, vec); extern unsigned num_loop_branches (const class loop *); extern edge loop_preheader_edge (const class loop *); extern edge loop_latch_edge (const class loop *); extern void add_bb_to_loop (basic_block, class loop *); extern void remove_bb_from_loops (basic_block); extern void cancel_loop_tree (class loop *); extern void delete_loop (class loop *); extern void verify_loop_structure (void); /* Loop analysis. */ extern bool just_once_each_iteration_p (const class loop *, const_basic_block); gcov_type expected_loop_iterations_unbounded (const class loop *, bool *read_profile_p = NULL, bool by_profile_only = false); extern unsigned expected_loop_iterations (class loop *); extern rtx doloop_condition_get (rtx_insn *); void mark_loop_for_removal (loop_p); /* Induction variable analysis. */ /* The description of induction variable. The things are a bit complicated due to need to handle subregs and extends. The value of the object described by it can be obtained as follows (all computations are done in extend_mode): Value in i-th iteration is delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)). If first_special is true, the value in the first iteration is delta + mult * base If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is subreg_{mode} (base + i * step) The get_iv_value function can be used to obtain these expressions. ??? Add a third mode field that would specify the mode in that inner computation is done, which would enable it to be different from the outer one? */ class rtx_iv { public: /* Its base and step (mode of base and step is supposed to be extend_mode, see the description above). */ rtx base, step; /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND, or IV_UNKNOWN_EXTEND). */ enum iv_extend_code extend; /* Operations applied in the extended mode. */ rtx delta, mult; /* The mode it is extended to. */ scalar_int_mode extend_mode; /* The mode the variable iterates in. */ scalar_int_mode mode; /* Whether the first iteration needs to be handled specially. */ unsigned first_special : 1; }; /* The description of an exit from the loop and of the number of iterations till we take the exit. */ class GTY(()) niter_desc { public: /* The edge out of the loop. */ edge out_edge; /* The other edge leading from the condition. */ edge in_edge; /* True if we are able to say anything about number of iterations of the loop. */ bool simple_p; /* True if the loop iterates the constant number of times. */ bool const_iter; /* Number of iterations if constant. */ uint64_t niter; /* Assumptions under that the rest of the information is valid. */ rtx assumptions; /* Assumptions under that the loop ends before reaching the latch, even if value of niter_expr says otherwise. */ rtx noloop_assumptions; /* Condition under that the loop is infinite. */ rtx infinite; /* Whether the comparison is signed. */ bool signed_p; /* The mode in that niter_expr should be computed. */ scalar_int_mode mode; /* The number of iterations of the loop. */ rtx niter_expr; }; extern void iv_analysis_loop_init (class loop *); extern bool iv_analyze (rtx_insn *, scalar_int_mode, rtx, class rtx_iv *); extern bool iv_analyze_result (rtx_insn *, rtx, class rtx_iv *); extern bool iv_analyze_expr (rtx_insn *, scalar_int_mode, rtx, class rtx_iv *); extern rtx get_iv_value (class rtx_iv *, rtx); extern bool biv_p (rtx_insn *, scalar_int_mode, rtx); extern void iv_analysis_done (void); extern class niter_desc *get_simple_loop_desc (class loop *loop); extern void free_simple_loop_desc (class loop *loop); static inline class niter_desc * simple_loop_desc (class loop *loop) { return loop->simple_loop_desc; } /* Accessors for the loop structures. */ /* Returns the loop with index NUM from FNs loop tree. */ static inline class loop * get_loop (struct function *fn, unsigned num) { return (*loops_for_fn (fn)->larray)[num]; } /* Returns the number of superloops of LOOP. */ static inline unsigned loop_depth (const class loop *loop) { return vec_safe_length (loop->superloops); } /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost loop. */ static inline class loop * loop_outer (const class loop *loop) { unsigned n = vec_safe_length (loop->superloops); if (n == 0) return NULL; return (*loop->superloops)[n - 1]; } /* Returns true if LOOP has at least one exit edge. */ static inline bool loop_has_exit_edges (const class loop *loop) { return loop->exits->next->e != NULL; } /* Returns the list of loops in FN. */ inline vec * get_loops (struct function *fn) { struct loops *loops = loops_for_fn (fn); if (!loops) return NULL; return loops->larray; } /* Returns the number of loops in FN (including the removed ones and the fake loop that forms the root of the loop tree). */ static inline unsigned number_of_loops (struct function *fn) { struct loops *loops = loops_for_fn (fn); if (!loops) return 0; return vec_safe_length (loops->larray); } /* Returns true if state of the loops satisfies all properties described by FLAGS. */ static inline bool loops_state_satisfies_p (function *fn, unsigned flags) { return (loops_for_fn (fn)->state & flags) == flags; } static inline bool loops_state_satisfies_p (unsigned flags) { return loops_state_satisfies_p (cfun, flags); } /* Sets FLAGS to the loops state. */ static inline void loops_state_set (function *fn, unsigned flags) { loops_for_fn (fn)->state |= flags; } static inline void loops_state_set (unsigned flags) { loops_state_set (cfun, flags); } /* Clears FLAGS from the loops state. */ static inline void loops_state_clear (function *fn, unsigned flags) { loops_for_fn (fn)->state &= ~flags; } static inline void loops_state_clear (unsigned flags) { if (!current_loops) return; loops_state_clear (cfun, flags); } /* Check loop structure invariants, if internal consistency checks are enabled. */ static inline void checking_verify_loop_structure (void) { /* VERIFY_LOOP_STRUCTURE essentially asserts that no loops need fixups. The loop optimizers should never make changes to the CFG which require loop fixups. But the low level CFG manipulation code may set the flag conservatively. Go ahead and clear the flag here. That avoids the assert inside VERIFY_LOOP_STRUCTURE, and if there is an inconsistency in the loop structures VERIFY_LOOP_STRUCTURE will detect it. This also avoid the compile time cost of excessive fixups. */ loops_state_clear (LOOPS_NEED_FIXUP); if (flag_checking) verify_loop_structure (); } /* Loop iterators. */ /* Flags for loop iteration. */ enum li_flags { LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */ LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order, starting from innermost ones. */ LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */ }; /* The iterator for loops. */ class loop_iterator { public: loop_iterator (function *fn, loop_p *loop, unsigned flags); inline loop_p next (); /* The function we are visiting. */ function *fn; /* The list of loops to visit. */ auto_vec to_visit; /* The index of the actual loop. */ unsigned idx; }; inline loop_p loop_iterator::next () { int anum; while (this->to_visit.iterate (this->idx, &anum)) { this->idx++; loop_p loop = get_loop (fn, anum); if (loop) return loop; } return NULL; } inline loop_iterator::loop_iterator (function *fn, loop_p *loop, unsigned flags) { class loop *aloop; unsigned i; int mn; this->idx = 0; this->fn = fn; if (!loops_for_fn (fn)) { *loop = NULL; return; } this->to_visit.reserve_exact (number_of_loops (fn)); mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1; if (flags & LI_ONLY_INNERMOST) { for (i = 0; vec_safe_iterate (loops_for_fn (fn)->larray, i, &aloop); i++) if (aloop != NULL && aloop->inner == NULL && aloop->num >= mn) this->to_visit.quick_push (aloop->num); } else if (flags & LI_FROM_INNERMOST) { /* Push the loops to LI->TO_VISIT in postorder. */ for (aloop = loops_for_fn (fn)->tree_root; aloop->inner != NULL; aloop = aloop->inner) continue; while (1) { if (aloop->num >= mn) this->to_visit.quick_push (aloop->num); if (aloop->next) { for (aloop = aloop->next; aloop->inner != NULL; aloop = aloop->inner) continue; } else if (!loop_outer (aloop)) break; else aloop = loop_outer (aloop); } } else { /* Push the loops to LI->TO_VISIT in preorder. */ aloop = loops_for_fn (fn)->tree_root; while (1) { if (aloop->num >= mn) this->to_visit.quick_push (aloop->num); if (aloop->inner != NULL) aloop = aloop->inner; else { while (aloop != NULL && aloop->next == NULL) aloop = loop_outer (aloop); if (aloop == NULL) break; aloop = aloop->next; } } } *loop = this->next (); } #define FOR_EACH_LOOP(LOOP, FLAGS) \ for (loop_iterator li(cfun, &(LOOP), FLAGS); \ (LOOP); \ (LOOP) = li.next ()) #define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \ for (loop_iterator li(FN, &(LOOP), FLAGS); \ (LOOP); \ (LOOP) = li.next ()) /* The properties of the target. */ struct target_cfgloop { /* Number of available registers. */ unsigned x_target_avail_regs; /* Number of available registers that are call-clobbered. */ unsigned x_target_clobbered_regs; /* Number of registers reserved for temporary expressions. */ unsigned x_target_res_regs; /* The cost for register when there still is some reserve, but we are approaching the number of available registers. */ unsigned x_target_reg_cost[2]; /* The cost for register when we need to spill. */ unsigned x_target_spill_cost[2]; }; extern struct target_cfgloop default_target_cfgloop; #if SWITCHABLE_TARGET extern struct target_cfgloop *this_target_cfgloop; #else #define this_target_cfgloop (&default_target_cfgloop) #endif #define target_avail_regs \ (this_target_cfgloop->x_target_avail_regs) #define target_clobbered_regs \ (this_target_cfgloop->x_target_clobbered_regs) #define target_res_regs \ (this_target_cfgloop->x_target_res_regs) #define target_reg_cost \ (this_target_cfgloop->x_target_reg_cost) #define target_spill_cost \ (this_target_cfgloop->x_target_spill_cost) /* Register pressure estimation for induction variable optimizations & loop invariant motion. */ extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool); extern void init_set_costs (void); /* Loop optimizer initialization. */ extern void loop_optimizer_init (unsigned); extern void loop_optimizer_finalize (function *); inline void loop_optimizer_finalize () { loop_optimizer_finalize (cfun); } /* Optimization passes. */ enum { UAP_UNROLL = 1, /* Enables unrolling of loops if it seems profitable. */ UAP_UNROLL_ALL = 2 /* Enables unrolling of all loops. */ }; extern void doloop_optimize_loops (void); extern void move_loop_invariants (void); extern vec get_loop_hot_path (const class loop *loop); /* Returns the outermost loop of the loop nest that contains LOOP.*/ static inline class loop * loop_outermost (class loop *loop) { unsigned n = vec_safe_length (loop->superloops); if (n <= 1) return loop; return (*loop->superloops)[1]; } extern void record_niter_bound (class loop *, const widest_int &, bool, bool); extern HOST_WIDE_INT get_estimated_loop_iterations_int (class loop *); extern HOST_WIDE_INT get_max_loop_iterations_int (const class loop *); extern HOST_WIDE_INT get_likely_max_loop_iterations_int (class loop *); extern bool get_estimated_loop_iterations (class loop *loop, widest_int *nit); extern bool get_max_loop_iterations (const class loop *loop, widest_int *nit); extern bool get_likely_max_loop_iterations (class loop *loop, widest_int *nit); extern int bb_loop_depth (const_basic_block); /* Converts VAL to widest_int. */ static inline widest_int gcov_type_to_wide_int (gcov_type val) { HOST_WIDE_INT a[2]; a[0] = (unsigned HOST_WIDE_INT) val; /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by the size of type. */ val >>= HOST_BITS_PER_WIDE_INT - 1; val >>= 1; a[1] = (unsigned HOST_WIDE_INT) val; return widest_int::from_array (a, 2); } #endif /* GCC_CFGLOOP_H */