Bug Summary

File:build/gcc/ccmp.cc
Warning:line 250, column 18
Assigned value is garbage or undefined

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-suse-linux -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name ccmp.cc -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model static -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/buildworker/marxinbox-gcc-clang-static-analyzer/objdir/gcc -resource-dir /usr/lib64/clang/15.0.7 -D IN_GCC -D HAVE_CONFIG_H -I . -I . -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/. -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../include -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../libcpp/include -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../libcody -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../libdecnumber -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../libdecnumber/bid -I ../libdecnumber -I /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/../libbacktrace -internal-isystem /usr/bin/../lib64/gcc/x86_64-suse-linux/13/../../../../include/c++/13 -internal-isystem /usr/bin/../lib64/gcc/x86_64-suse-linux/13/../../../../include/c++/13/x86_64-suse-linux -internal-isystem /usr/bin/../lib64/gcc/x86_64-suse-linux/13/../../../../include/c++/13/backward -internal-isystem /usr/lib64/clang/15.0.7/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/gcc/x86_64-suse-linux/13/../../../../x86_64-suse-linux/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-narrowing -Wwrite-strings -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -fdeprecated-macro -fdebug-compilation-dir=/buildworker/marxinbox-gcc-clang-static-analyzer/objdir/gcc -ferror-limit 19 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=plist-html -analyzer-config silence-checkers=core.NullDereference -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /buildworker/marxinbox-gcc-clang-static-analyzer/objdir/clang-static-analyzer/2023-03-27-141847-20772-1/report-1BZHeF.plist -x c++ /buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc
1/* Conditional compare related functions
2 Copyright (C) 2014-2023 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3. If not see
18<http://www.gnu.org/licenses/>. */
19
20#include "config.h"
21#include "system.h"
22#include "coretypes.h"
23#include "backend.h"
24#include "target.h"
25#include "rtl.h"
26#include "tree.h"
27#include "gimple.h"
28#include "memmodel.h"
29#include "tm_p.h"
30#include "ssa.h"
31#include "expmed.h"
32#include "optabs.h"
33#include "emit-rtl.h"
34#include "stor-layout.h"
35#include "tree-ssa-live.h"
36#include "tree-outof-ssa.h"
37#include "cfgexpand.h"
38#include "ccmp.h"
39#include "predict.h"
40
41/* Check whether T is a simple boolean variable or a SSA name
42 set by a comparison operator in the same basic block. */
43static bool
44ccmp_tree_comparison_p (tree t, basic_block bb)
45{
46 gimple *g = get_gimple_for_ssa_name (t);
47 tree_code tcode;
48
49 /* If we have a boolean variable allow it and generate a compare
50 to zero reg when expanding. */
51 if (!g)
52 return (TREE_CODE (TREE_TYPE (t))((enum tree_code) (((contains_struct_check ((t), (TS_TYPED), "/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 52, __FUNCTION__))->typed.type))->base.code) == BOOLEAN_TYPE);
53
54 /* Check to see if SSA name is set by a comparison operator in
55 the same basic block. */
56 if (!is_gimple_assign (g))
57 return false;
58 if (bb != gimple_bb (g))
59 return false;
60 tcode = gimple_assign_rhs_code (g);
61 return TREE_CODE_CLASS (tcode)tree_code_type_tmpl <0>::tree_code_type[(int) (tcode)] == tcc_comparison;
62}
63
64/* The following functions expand conditional compare (CCMP) instructions.
65 Here is a short description about the over all algorithm:
66 * ccmp_candidate_p is used to identify the CCMP candidate
67
68 * expand_ccmp_expr is the main entry, which calls expand_ccmp_expr_1
69 to expand CCMP.
70
71 * expand_ccmp_expr_1 uses a recursive algorithm to expand CCMP.
72 It calls two target hooks gen_ccmp_first and gen_ccmp_next to generate
73 CCMP instructions.
74 - gen_ccmp_first expands the first compare in CCMP.
75 - gen_ccmp_next expands the following compares.
76
77 Both hooks return a comparison with the CC register that is equivalent
78 to the value of the gimple comparison. This is used by the next CCMP
79 and in the final conditional store.
80
81 * We use cstorecc4 pattern to convert the CCmode intermediate to
82 the integer mode result that expand_normal is expecting.
83
84 Since the operands of the later compares might clobber CC reg, we do not
85 emit the insns during expand. We keep the insn sequences in two seq
86
87 * prep_seq, which includes all the insns to prepare the operands.
88 * gen_seq, which includes all the compare and conditional compares.
89
90 If all checks OK in expand_ccmp_expr, it emits insns in prep_seq, then
91 insns in gen_seq. */
92
93/* Check whether G is a potential conditional compare candidate. */
94static bool
95ccmp_candidate_p (gimple *g)
96{
97 tree lhs, op0, op1;
98 gimple *gs0, *gs1;
99 tree_code tcode;
100 basic_block bb;
101
102 if (!g)
103 return false;
104
105 tcode = gimple_assign_rhs_code (g);
106 if (tcode != BIT_AND_EXPR && tcode != BIT_IOR_EXPR)
107 return false;
108
109 lhs = gimple_assign_lhs (g);
110 op0 = gimple_assign_rhs1 (g);
111 op1 = gimple_assign_rhs2 (g);
112 if ((TREE_CODE (op0)((enum tree_code) (op0)->base.code) != SSA_NAME) || (TREE_CODE (op1)((enum tree_code) (op1)->base.code) != SSA_NAME)
113 || !has_single_use (lhs))
114 return false;
115
116 bb = gimple_bb (g);
117 gs0 = get_gimple_for_ssa_name (op0); /* gs0 may be NULL */
118 gs1 = get_gimple_for_ssa_name (op1); /* gs1 may be NULL */
119
120 if (ccmp_tree_comparison_p (op0, bb) && ccmp_tree_comparison_p (op1, bb))
121 return true;
122 if (ccmp_tree_comparison_p (op0, bb) && ccmp_candidate_p (gs1))
123 return true;
124 if (ccmp_tree_comparison_p (op1, bb) && ccmp_candidate_p (gs0))
125 return true;
126 /* We skip ccmp_candidate_p (gs1) && ccmp_candidate_p (gs0) since
127 there is no way to set and maintain the CC flag on both sides of
128 the logical operator at the same time. */
129 return false;
130}
131
132/* Extract the comparison we want to do from the tree. */
133void
134get_compare_parts (tree t, int *up, rtx_code *rcode,
135 tree *rhs1, tree *rhs2)
136{
137 tree_code code;
138 gimple *g = get_gimple_for_ssa_name (t);
139 if (g)
140 {
141 *up = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (g)))((tree_class_check ((((contains_struct_check ((gimple_assign_rhs1
(g)), (TS_TYPED), "/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 141, __FUNCTION__))->typed.type)), (tcc_type), "/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 141, __FUNCTION__))->base.u.bits.unsigned_flag);
142 code = gimple_assign_rhs_code (g);
143 *rcode = get_rtx_code (code, *up);
144 *rhs1 = gimple_assign_rhs1 (g);
145 *rhs2 = gimple_assign_rhs2 (g);
146 }
147 else
148 {
149 /* If g is not a comparison operator create a compare to zero. */
150 *up = 1;
151 *rcode = NE;
152 *rhs1 = t;
153 *rhs2 = build_zero_cst (TREE_TYPE (t)((contains_struct_check ((t), (TS_TYPED), "/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 153, __FUNCTION__))->typed.type));
154 }
155}
156
157/* PREV is a comparison with the CC register which represents the
158 result of the previous CMP or CCMP. The function expands the
159 next compare based on G which is ANDed/ORed with the previous
160 compare depending on CODE.
161 PREP_SEQ returns all insns to prepare opearands for compare.
162 GEN_SEQ returns all compare insns. */
163static rtx
164expand_ccmp_next (tree op, tree_code code, rtx prev,
165 rtx_insn **prep_seq, rtx_insn **gen_seq)
166{
167 rtx_code rcode;
168 int unsignedp;
169 tree rhs1, rhs2;
170
171 get_compare_parts(op, &unsignedp, &rcode, &rhs1, &rhs2);
172 return targetm.gen_ccmp_next (prep_seq, gen_seq, prev, rcode,
173 rhs1, rhs2, get_rtx_code (code, 0));
174}
175
176/* Expand conditional compare gimple G. A typical CCMP sequence is like:
177
178 CC0 = CMP (a, b);
179 CC1 = CCMP (NE (CC0, 0), CMP (e, f));
180 ...
181 CCn = CCMP (NE (CCn-1, 0), CMP (...));
182
183 hook gen_ccmp_first is used to expand the first compare.
184 hook gen_ccmp_next is used to expand the following CCMP.
185 PREP_SEQ returns all insns to prepare opearand.
186 GEN_SEQ returns all compare insns. */
187static rtx
188expand_ccmp_expr_1 (gimple *g, rtx_insn **prep_seq, rtx_insn **gen_seq)
189{
190 tree_code code = gimple_assign_rhs_code (g);
191 basic_block bb = gimple_bb (g);
192
193 tree op0 = gimple_assign_rhs1 (g);
194 tree op1 = gimple_assign_rhs2 (g);
195 gimple *gs0 = get_gimple_for_ssa_name (op0);
196 gimple *gs1 = get_gimple_for_ssa_name (op1);
197 rtx tmp;
198
199 gcc_assert (code == BIT_AND_EXPR || code == BIT_IOR_EXPR)((void)(!(code == BIT_AND_EXPR || code == BIT_IOR_EXPR) ? fancy_abort
("/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 199, __FUNCTION__), 0 : 0));
3
←
'?' condition is false
→
200
201 if (ccmp_tree_comparison_p (op0, bb))
4
←
Taking true branch
→
202 {
203 if (ccmp_tree_comparison_p (op1, bb))
5
←
Taking true branch
→
204 {
205 int unsignedp0, unsignedp1;
206 rtx_code rcode0, rcode1;
207 tree logical_op0_rhs1, logical_op0_rhs2;
208 tree logical_op1_rhs1, logical_op1_rhs2;
209 int speed_p = optimize_insn_for_speed_p ();
210
211 rtx tmp2 = NULL_RTX(rtx) 0, ret = NULL_RTX(rtx) 0, ret2 = NULL_RTX(rtx) 0;
212 unsigned cost1 = MAX_COST2147483647;
213 unsigned cost2 = MAX_COST2147483647;
214
215 get_compare_parts (op0, &unsignedp0, &rcode0,
216 &logical_op0_rhs1, &logical_op0_rhs2);
217
218 get_compare_parts (op1, &unsignedp1, &rcode1,
219 &logical_op1_rhs1, &logical_op1_rhs2);
220
221 rtx_insn *prep_seq_1, *gen_seq_1;
222 tmp = targetm.gen_ccmp_first (&prep_seq_1, &gen_seq_1, rcode0,
223 logical_op0_rhs1, logical_op0_rhs2);
224 if (tmp != NULLnullptr)
6
←
Assuming the condition is true
→
7
←
Taking true branch
→
225 {
226 ret = expand_ccmp_next (op1, code, tmp, &prep_seq_1, &gen_seq_1);
227 cost1 = seq_cost (prep_seq_1, speed_p);
228 cost1 += seq_cost (gen_seq_1, speed_p);
229 }
230
231 /* FIXME: Temporary workaround for PR69619.
232 Avoid exponential compile time due to expanding gs0 and gs1 twice.
233 If gs0 and gs1 are complex, the cost will be high, so avoid
234 reevaluation if above an arbitrary threshold. */
235 rtx_insn *prep_seq_2, *gen_seq_2;
8
←
'prep_seq_2' declared without an initial value
→
236 if (tmp == NULLnullptr || cost1 < COSTS_N_INSNS (25)((25) * 4))
9
←
Assuming the condition is false
→
237 tmp2 = targetm.gen_ccmp_first (&prep_seq_2, &gen_seq_2, rcode1,
238 logical_op1_rhs1, logical_op1_rhs2);
239 if (!tmp
9.1
'tmp' is non-null
 && !tmp2)
240 return NULL_RTX(rtx) 0;
241 if (tmp2 != NULLnullptr)
10
←
Taking false branch
→
242 {
243 ret2 = expand_ccmp_next (op0, code, tmp2, &prep_seq_2,
244 &gen_seq_2);
245 cost2 = seq_cost (prep_seq_2, speed_p);
246 cost2 += seq_cost (gen_seq_2, speed_p);
247 }
248 if (cost2 < cost1)
11
←
Assuming 'cost2' is < 'cost1'
→
12
←
Taking true branch
→
249 {
250 *prep_seq = prep_seq_2;
13
←
Assigned value is garbage or undefined
251 *gen_seq = gen_seq_2;
252 return ret2;
253 }
254 *prep_seq = prep_seq_1;
255 *gen_seq = gen_seq_1;
256 return ret;
257 }
258 else
259 {
260 tmp = expand_ccmp_expr_1 (gs1, prep_seq, gen_seq);
261 if (!tmp)
262 return NULL_RTX(rtx) 0;
263 return expand_ccmp_next (op0, code, tmp, prep_seq, gen_seq);
264 }
265 }
266 else
267 {
268 gcc_assert (gimple_assign_rhs_code (gs0) == BIT_AND_EXPR((void)(!(gimple_assign_rhs_code (gs0) == BIT_AND_EXPR || gimple_assign_rhs_code
(gs0) == BIT_IOR_EXPR) ? fancy_abort ("/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 269, __FUNCTION__), 0 : 0))
269 || gimple_assign_rhs_code (gs0) == BIT_IOR_EXPR)((void)(!(gimple_assign_rhs_code (gs0) == BIT_AND_EXPR || gimple_assign_rhs_code
(gs0) == BIT_IOR_EXPR) ? fancy_abort ("/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 269, __FUNCTION__), 0 : 0));
270 gcc_assert (ccmp_tree_comparison_p (op1, bb))((void)(!(ccmp_tree_comparison_p (op1, bb)) ? fancy_abort ("/buildworker/marxinbox-gcc-clang-static-analyzer/build/gcc/ccmp.cc"
, 270, __FUNCTION__), 0 : 0));
271 tmp = expand_ccmp_expr_1 (gs0, prep_seq, gen_seq);
272 if (!tmp)
273 return NULL_RTX(rtx) 0;
274 return expand_ccmp_next (op1, code, tmp, prep_seq, gen_seq);
275 }
276}
277
278/* Main entry to expand conditional compare statement G.
279 Return NULL_RTX if G is not a legal candidate or expand fail.
280 Otherwise return the target. */
281rtx
282expand_ccmp_expr (gimple *g, machine_mode mode)
283{
284 rtx_insn *last;
285 rtx tmp;
286
287 if (!ccmp_candidate_p (g))
1
Taking false branch
→
288 return NULL_RTX(rtx) 0;
289
290 last = get_last_insn ();
291
292 rtx_insn *prep_seq = NULLnullptr, *gen_seq = NULLnullptr;
293 tmp = expand_ccmp_expr_1 (g, &prep_seq, &gen_seq);
2
←
Calling 'expand_ccmp_expr_1'
→
294
295 if (tmp)
296 {
297 insn_code icode;
298 machine_mode cc_mode = CCmode((void) 0, E_CCmode);
299 rtx_code cmp_code = GET_CODE (tmp)((enum rtx_code) (tmp)->code);
300
301#ifdef SELECT_CC_MODE
302 cc_mode = SELECT_CC_MODE (cmp_code, XEXP (tmp, 0), const0_rtx)ix86_cc_mode ((cmp_code), ((((tmp)->u.fld[0]).rt_rtx)), ((
const_int_rtx[64])));
303#endif
304 icode = optab_handler (cstore_optab, cc_mode);
305 if (icode != CODE_FOR_nothing)
306 {
307 rtx target = gen_reg_rtx (mode);
308
309 emit_insn (prep_seq);
310 emit_insn (gen_seq);
311
312 tmp = emit_cstore (target, icode, cmp_code, cc_mode, cc_mode,
313 0, XEXP (tmp, 0)(((tmp)->u.fld[0]).rt_rtx), const0_rtx(const_int_rtx[64]), 1, mode);
314 if (tmp)
315 return tmp;
316 }
317 }
318 /* Clean up. */
319 delete_insns_since (last);
320 return NULL_RTX(rtx) 0;
321}