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| author | Jakub Jelinek <jakub@redhat.com> | 2024-09-03 10:20:44 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2024-09-03 10:21:53 +0200 |
| commit | d4d75a83007e884bfcd632ea3b3269704496f048 (patch) | |
| tree | 2199450388d22989b97f333eb3b5c6c862b52e79 | |
| parent | a19cf635ea29658d5f9fc19199473d6d823ef2d1 (diff) | |
| download | gcc-d4d75a83007e884bfcd632ea3b3269704496f048.zip gcc-d4d75a83007e884bfcd632ea3b3269704496f048.tar.gz gcc-d4d75a83007e884bfcd632ea3b3269704496f048.tar.bz2 | |
lower-bitint: Fix up __builtin_{add,sub}_overflow{,_p} bitint lowering [PR116501]
The following testcase is miscompiled. The problem is in the last_ovf step.
The second operand has signed _BitInt(513) type but has the MSB clear,
so range_to_prec returns 512 for it (i.e. it fits into unsigned
_BitInt(512)). Because of that the last step actually doesn't need to get
the most significant bit from the second operand, but the code was deciding
what to use purely from TYPE_UNSIGNED (type1) - if unsigned, use 0,
otherwise sign-extend the last processed bit; but that in this case was set.
We don't want to treat the positive operand as if it was negative regardless
of the bit below that precision, and precN >= 0 indicates that the operand
is in the [0, inf) range.
2024-09-03 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/116501
* gimple-lower-bitint.cc (bitint_large_huge::lower_addsub_overflow):
In the last_ovf case, use build_zero_cst operand not just when
TYPE_UNSIGNED (typeN), but also when precN >= 0.
* gcc.dg/torture/bitint-73.c: New test.
| -rw-r--r-- | gcc/gimple-lower-bitint.cc | 4 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/torture/bitint-73.c | 20 |
2 files changed, 22 insertions, 2 deletions
diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc index b105930..58deaf2 100644 --- a/gcc/gimple-lower-bitint.cc +++ b/gcc/gimple-lower-bitint.cc @@ -4192,7 +4192,7 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt) else { m_data_cnt = data_cnt; - if (TYPE_UNSIGNED (type0)) + if (TYPE_UNSIGNED (type0) || prec0 >= 0) rhs1 = build_zero_cst (m_limb_type); else { @@ -4210,7 +4210,7 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt) rhs1 = add_cast (m_limb_type, gimple_assign_lhs (g)); } } - if (TYPE_UNSIGNED (type1)) + if (TYPE_UNSIGNED (type1) || prec1 >= 0) rhs2 = build_zero_cst (m_limb_type); else { diff --git a/gcc/testsuite/gcc.dg/torture/bitint-73.c b/gcc/testsuite/gcc.dg/torture/bitint-73.c new file mode 100644 index 0000000..1e15f39 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/bitint-73.c @@ -0,0 +1,20 @@ +/* PR tree-optimization/116501 */ +/* { dg-do run { target bitint575 } } */ +/* { dg-options "-std=c23" } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */ + +_BitInt (4) a; + +int +foo (_BitInt(513) b) +{ + return __builtin_sub_overflow_p (a, b, (_BitInt (511)) 0); +} + +int +main () +{ + if (!foo (0xffffffffffffffff0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff0000000000000000wb)) + __builtin_abort (); +} |