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1 : // Definition of private classes for RTL SSA -*- C++ -*-
2 : // Copyright (C) 2020-2026 Free Software Foundation, Inc.
3 : //
4 : // This file is part of GCC.
5 : //
6 : // GCC is free software; you can redistribute it and/or modify it under
7 : // the terms of the GNU General Public License as published by the Free
8 : // Software Foundation; either version 3, or (at your option) any later
9 : // version.
10 : //
11 : // GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 : // WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 : // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 : // for more details.
15 : //
16 : // You should have received a copy of the GNU General Public License
17 : // along with GCC; see the file COPYING3. If not see
18 : // <http://www.gnu.org/licenses/>.
19 :
20 : namespace rtl_ssa {
21 :
22 : // Information about a basic block's phi nodes. This class is only used when
23 : // constructing the SSA form, it isn't meant to be kept up-to-date.
24 76734318 : class function_info::bb_phi_info
25 : {
26 : public:
27 : // The set of registers that need phi nodes.
28 : bitmap_head regs;
29 :
30 : // The number of registers in REGS.
31 : unsigned int num_phis;
32 :
33 : // The number of inputs to each phi node. Caching the information here
34 : // is at best a minor optimisation, but it fills a 32-bit hole that would
35 : // otherwise exist on 64-bit hosts.
36 : unsigned int num_preds;
37 :
38 : // An array of all the phi inputs for this block. It lists all inputs
39 : // from the first incoming edge followed by all inputs for the next
40 : // incoming edge, and so on. The inputs for a given edge are sorted
41 : // by increasing register number.
42 : set_info **inputs;
43 : };
44 :
45 : // Information used while constructing the SSA form and discarded
46 : // afterwards.
47 : class function_info::build_info
48 : {
49 : public:
50 : build_info (unsigned int, unsigned int);
51 : ~build_info ();
52 :
53 : set_info *current_reg_value (unsigned int) const;
54 : set_info *current_mem_value () const;
55 :
56 : void record_reg_def (def_info *);
57 : void record_mem_def (def_info *);
58 :
59 : // The block that we're currently processing.
60 : bb_info *current_bb;
61 :
62 : // The EBB that contains CURRENT_BB.
63 : ebb_info *current_ebb;
64 :
65 : // Except for the local exception noted below:
66 : //
67 : // - If register R has been defined in the current EBB, LAST_ACCESS[R + 1]
68 : // is the last definition of R in the EBB.
69 : //
70 : // - Otherwise, if the current EBB is dominated by a definition of R,
71 : // LAST_ACCESS[R + 1] is the nearest dominating definition.
72 : //
73 : // - Otherwise, LAST_ACCESS[R + 1] is null.
74 : //
75 : // Similarly:
76 : //
77 : // - If the current EBB has defined memory, LAST_ACCESS[0] is the last
78 : // definition of memory in the EBB.
79 : //
80 : // - Otherwise LAST_ACCESS[0] is the value of memory that is live on
81 : // - entry to the EBB.
82 : //
83 : // The exception is that while building instructions, LAST_ACCESS[I]
84 : // can temporarily be the use of regno I - 1 by that instruction.
85 : auto_vec<access_info *> last_access;
86 :
87 : // A bitmap used to hold EBB_LIVE_IN_FOR_DEBUG.
88 : auto_bitmap tmp_ebb_live_in_for_debug;
89 :
90 : // If nonnull, a bitmap of registers that are live on entry to this EBB,
91 : // with a tree view for quick lookup. This bitmap is calculated lazily
92 : // and is only used if MAY_HAVE_DEBUG_INSNS.
93 : bitmap ebb_live_in_for_debug;
94 :
95 : // The set of registers that might need to have phis associated with them.
96 : // Registers outside this set are known to have a single definition that
97 : // dominates all uses.
98 : //
99 : // Before RA, about 5% of registers are typically in the set.
100 : auto_sbitmap potential_phi_regs;
101 :
102 : // A sparse bitmap representation of POTENTIAL_PHI_REGS. Only used if
103 : // MAY_HAVE_DEBUG_INSNS.
104 : auto_bitmap potential_phi_regs_for_debug;
105 :
106 : // The set of registers that have been defined so far in the current EBB.
107 : auto_bitmap ebb_def_regs;
108 :
109 : // BB_PHIS[B] describes the phis for basic block B.
110 : auto_vec<bb_phi_info> bb_phis;
111 :
112 : // BB_MEM_LIVE_OUT[B] is the memory value that is live on exit from
113 : // basic block B.
114 : auto_vec<set_info *> bb_mem_live_out;
115 :
116 : // BB_TO_RPO[B] gives the position of block B in a reverse postorder
117 : // of the CFG. The RPO is a tweaked version of the one normally
118 : // returned by pre_and_rev_post_order_compute, with all blocks in
119 : // an EBB having consecutive positions.
120 : auto_vec<int> bb_to_rpo;
121 :
122 : // This stack is divided into sections, with one section for the
123 : // current basic block and one section for each dominating block.
124 : // Each element is a register definition.
125 : //
126 : // If the section for block B contains a definition D of a register R,
127 : // then one of two things is true:
128 : //
129 : // - D occurs in B and no definition of R dominates B.
130 : // - D dominates B and is the nearest dominating definition of R.
131 : //
132 : // The two cases are distinguished by the value of D->bb ().
133 : auto_vec<def_info *> def_stack;
134 :
135 : // The top of this stack records the start of the current block's
136 : // section in DEF_STACK.
137 : auto_vec<unsigned int> old_def_stack_limit;
138 :
139 : // The block that dominates the exit block, or null if the exit block
140 : // is unreachable.
141 : basic_block exit_block_dominator;
142 : };
143 :
144 : }
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