https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100204
Bug ID: 100204
Summary: aarch64: UB evaluating J constraint
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: acoplan at gcc dot gnu.org
Target Milestone: ---
On AArch64 with UBSan, the following testcase (reduced from
c-c++-common/torture/builtin-arith-overflow-10.c) shows us invoking UB while
evaluating the "J" constraint:
$ cat test.c
long a();
unsigned b(long);
void c() {
int d, e;
for (d = 0;; d++)
for (e = 0; e < (char)~0; e++) {
long f = d - 9223372036854775807, g = e - 9223372036854775807 - 1;
__int128 h = f + g;
if (a() != h)
if (b(g) != h)
__builtin_abort();
}
}
$ gcc/xgcc -B gcc test.c -c -O
/home/alecop01/toolchain/src/gcc/gcc/config/aarch64/constraints.md:86:23:
runtime error: negation of -9223372036854775808 cannot be represented in type
'long int'; cast to an unsigned type to negate this value to itself
#0 0x434aa1c in insn_const_int_ok_for_constraint(long, constraint_num)
/home/alecop01/toolchain/src/gcc/gcc/config/aarch64/constraints.md:86
#1 0x18892ec in process_alt_operands
/home/alecop01/toolchain/src/gcc/gcc/lra-constraints.c:2420
#2 0x18892ec in curr_insn_transform
/home/alecop01/toolchain/src/gcc/gcc/lra-constraints.c:4108
#3 0x189df28 in lra_constraints(bool)
/home/alecop01/toolchain/src/gcc/gcc/lra-constraints.c:5174
#4 0x1832cd4 in lra(_IO_FILE*)
/home/alecop01/toolchain/src/gcc/gcc/lra.c:2336
#5 0x16d1784 in do_reload /home/alecop01/toolchain/src/gcc/gcc/ira.c:5835
#6 0x16d1784 in execute /home/alecop01/toolchain/src/gcc/gcc/ira.c:6021
#7 0x1b5ec1c in execute_one_pass(opt_pass*)
/home/alecop01/toolchain/src/gcc/gcc/passes.c:2567
#8 0x1b623b8 in execute_pass_list_1
/home/alecop01/toolchain/src/gcc/gcc/passes.c:2656
#9 0x1b623f0 in execute_pass_list_1
/home/alecop01/toolchain/src/gcc/gcc/passes.c:2657
#10 0x1b624d4 in execute_pass_list(function*, opt_pass*)
/home/alecop01/toolchain/src/gcc/gcc/passes.c:2667
#11 0xc7b2a4 in cgraph_node::expand()
/home/alecop01/toolchain/src/gcc/gcc/cgraphunit.c:1830
#12 0xc7ff24 in expand_all_functions
/home/alecop01/toolchain/src/gcc/gcc/cgraphunit.c:1994
#13 0xc7ff24 in symbol_table::compile()
/home/alecop01/toolchain/src/gcc/gcc/cgraphunit.c:2358
#14 0xc8b81c in symbol_table::compile()
/home/alecop01/toolchain/src/gcc/gcc/cgraphunit.c:2271
#15 0xc8b81c in symbol_table::finalize_compilation_unit()
/home/alecop01/toolchain/src/gcc/gcc/cgraphunit.c:2539
#16 0x1f97478 in compile_file
/home/alecop01/toolchain/src/gcc/gcc/toplev.c:482
#17 0x68d9b0 in do_compile
/home/alecop01/toolchain/src/gcc/gcc/toplev.c:2201
#18 0x68d9b0 in toplev::main(int, char**)
/home/alecop01/toolchain/src/gcc/gcc/toplev.c:2340
#19 0x6910d0 in main /home/alecop01/toolchain/src/gcc/gcc/main.c:39
#20 0xffffa32db6dc in __libc_start_main
(/lib/aarch64-linux-gnu/libc.so.6+0x206dc)
#21 0x691b2c (/data/alecop01/builds/bstrap-ubsan/gcc/cc1+0x691b2c)
