From eef6aea3052b4b8a60df211015dafcb4573d19fb Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Sun, 3 Dec 2023 17:54:03 +0100 Subject: [PATCH] lower-bitint: Fix up lower_addsub_overflow [PR112807] lower_addsub_overflow uses handle_cast or handle_operand to extract current limb from the operands. Both of those functions heavily assume that they return a large or huge BITINT_TYPE. The problem in the testcase is that this is violated. Normally, lower_addsub_overflow isn't even called if neither the return's type element type nor any of the operand is large/huge BITINT_TYPE (on x86_64 129+ bits), for middle BITINT_TYPE (on x86_64 65-128 bits) some other code casts such operands to {,unsigned }__int128. In the testcase the result is complex unsigned, so small, but one of the arguments is _BitInt(256), so lower_addsub_overflow is called. But range_for_prec asks the ranger for ranges of the operands and in this case the first argument has [0, 0xffffffff] range and second [-2, 1], so unsigned 32-bit and signed 2-bit, and in such case the code for handle_operand/handle_cast purposes would use the _BitInt(256) type for the first operand (ok), but because prec3 aka maximum of result precision and the VRP computes ranges of the arguments is 32, use cast to 32-bit BITINT_TYPE, which is why it didn't work correctly. The following patch ensures that in such cases we use handle_cast to the type of the other argument. Perhaps incrementally, we could try to optimize this in an earlier phase, see that while the .{ADD,SUB}_OVERFLOW has large/huge _BitInt argument, as ranger says it fits into a smaller type, add a cast of the larger argument to the smaller precision type in which it fits. Either in gimple_lower_bitint, or match.pd. An argument for the latter is that e.g. complex unsigned .ADD_OVERFLOW (unsigned_long_long_arg, unsigned_arg) where ranger says unsigned_long_long_arg fits into unsigned 32-bit could be also more efficient as .ADD_OVERFLOW ((unsigned) unsigned_long_long_arg, unsigned_arg) 2023-12-03 Jakub Jelinek PR middle-end/112807 * gimple-lower-bitint.cc (bitint_large_huge::lower_addsub_overflow): When choosing type0 and type1 types, if prec3 has small/middle bitint kind, use maximum of type0 and type1's precision instead of prec3. * gcc.dg/bitint-46.c: New test. --- gcc/gimple-lower-bitint.cc | 11 +++++++---- gcc/testsuite/gcc.dg/bitint-46.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/bitint-46.c diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc index 6de869fa81c..01346f17ca7 100644 --- a/gcc/gimple-lower-bitint.cc +++ b/gcc/gimple-lower-bitint.cc @@ -3911,15 +3911,18 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt) tree type0 = TREE_TYPE (arg0); tree type1 = TREE_TYPE (arg1); - if (TYPE_PRECISION (type0) < prec3) + int prec5 = prec3; + if (bitint_precision_kind (prec5) < bitint_prec_large) + prec5 = MAX (TYPE_PRECISION (type0), TYPE_PRECISION (type1)); + if (TYPE_PRECISION (type0) < prec5) { - type0 = build_bitint_type (prec3, TYPE_UNSIGNED (type0)); + type0 = build_bitint_type (prec5, TYPE_UNSIGNED (type0)); if (TREE_CODE (arg0) == INTEGER_CST) arg0 = fold_convert (type0, arg0); } - if (TYPE_PRECISION (type1) < prec3) + if (TYPE_PRECISION (type1) < prec5) { - type1 = build_bitint_type (prec3, TYPE_UNSIGNED (type1)); + type1 = build_bitint_type (prec5, TYPE_UNSIGNED (type1)); if (TREE_CODE (arg1) == INTEGER_CST) arg1 = fold_convert (type1, arg1); } diff --git a/gcc/testsuite/gcc.dg/bitint-46.c b/gcc/testsuite/gcc.dg/bitint-46.c new file mode 100644 index 00000000000..4e503376d7f --- /dev/null +++ b/gcc/testsuite/gcc.dg/bitint-46.c @@ -0,0 +1,32 @@ +/* PR middle-end/112807 */ +/* { dg-do compile { target bitint } } */ +/* { dg-options "-std=gnu23 -O2" } */ + +#if __BITINT_MAXWIDTH__ >= 256 +__attribute__((noipa)) int +foo (_BitInt (256) a, _BitInt (2) b) +{ + if (a < 0 || a > ~0U) + return -1; + return __builtin_sub_overflow_p (a, b, 0); +} +#endif + +int +main () +{ +#if __BITINT_MAXWIDTH__ >= 256 + if (foo (-5wb, 1wb) != -1 + || foo (1 + (_BitInt (256)) ~0U, -2) != -1 + || foo (0, 0) != 0 + || foo (0, 1) != 0 + || foo (0, -1) != 0 + || foo (~0U, 0) != 1 + || foo (__INT_MAX__, 0) != 0 + || foo (__INT_MAX__, -1) != 1 + || foo (1 + (_BitInt (256)) __INT_MAX__, 0) != 1 + || foo (1 + (_BitInt (256)) __INT_MAX__, 1) != 0 + || foo (1 + (_BitInt (256)) __INT_MAX__, -2) != 1) + __builtin_abort (); +#endif +}