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From: Jakub Jelinek <jakub@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r14-9150] bitintlower: Fix .{ADD, SUB}_OVERFLOW lowering [PR114040] Date: Fri, 23 Feb 2024 10:37:05 +0000 (GMT) [thread overview] Message-ID: <20240223103705.EB4223858D1E@sourceware.org> (raw) https://gcc.gnu.org/g:be1f2bc4522f772184a4d16d8f3fec75baed89cf commit r14-9150-gbe1f2bc4522f772184a4d16d8f3fec75baed89cf Author: Jakub Jelinek <jakub@redhat.com> Date: Fri Feb 23 11:36:15 2024 +0100 bitintlower: Fix .{ADD,SUB}_OVERFLOW lowering [PR114040] The following testcases show 2 bugs in the .{ADD,SUB}_OVERFLOW lowering, both related to storing of the REALPART_EXPR part of the result. On the first testcase prec is 255, prec_limbs is 4 and for the second limb in the loop the store of the REALPART_EXPR of .USUBC (_30) is stored through: if (_27 <= 3) goto <bb 12>; [80.00%] else goto <bb 15>; [20.00%] <bb 12> [local count: 1073741824]: if (_27 < 3) goto <bb 14>; [80.00%] else goto <bb 13>; [20.00%] <bb 13> [local count: 1073741824]: bitint.3[_27] = _30; goto <bb 15>; [100.00%] <bb 14> [local count: 858993464]: MEM[(unsigned long *)&bitint.3 + 24B] = _30; <bb 15> [local count: 1073741824]: The first check is right, as prec_limbs is 4, we don't want to store bitint.3[4] or above at all, those limbs are just computed for the overflow checking and nothing else, so _27 > 4 leads to no store. But the other condition is exact opposite of what should be done, if the current index of the second limb (_27) is < 3, then it should bitint.3[_27] = _30; and if it is == 3, it should MEM[(unsigned long *)&bitint.3 + 24B] = _30; and (especially important for the targets which would bitinfo.extended = 1) should actually in this case zero extend it from the 63 bits to 64, that is the handling of the partial limb. The if_then_if_then_else helper if there are 2 conditions sets m_gsi to be at the start of the edge_true_false->dest bb, i.e. when the first condition is true and second false, and that is where we store the SSA_NAME indexed limb store, so the condition needs to be reversed. The following patch does that and adds the cast as well, the usual assumption that already handle_operand has the partial limb type doesn't have to be true here, because the source operand could have much larger precision than the REALPART_EXPR of the lhs. 2024-02-23 Jakub Jelinek <jakub@redhat.com> PR tree-optimization/114040 * gimple-lower-bitint.cc (bitint_large_huge::lower_addsub_overflow): Use EQ_EXPR rather than LT_EXPR for g2 condition and change its probability from likely to unlikely. When handling the true true store, first cast to limb_access_type and then to l's type. * gcc.dg/torture/bitint-60.c: New test. * gcc.dg/torture/bitint-61.c: New test. Diff: --- gcc/gimple-lower-bitint.cc | 11 ++++++---- gcc/testsuite/gcc.dg/torture/bitint-60.c | 24 +++++++++++++++++++++ gcc/testsuite/gcc.dg/torture/bitint-61.c | 36 ++++++++++++++++++++++++++++++++ 3 files changed, 67 insertions(+), 4 deletions(-) diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc index fb03063f86e4..3552fdd183e9 100644 --- a/gcc/gimple-lower-bitint.cc +++ b/gcc/gimple-lower-bitint.cc @@ -4255,12 +4255,12 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt) NULL_TREE, NULL_TREE); gimple *g2 = NULL; if (!single_comparison) - g2 = gimple_build_cond (LT_EXPR, idx, + g2 = gimple_build_cond (EQ_EXPR, idx, size_int (prec_limbs - 1), NULL_TREE, NULL_TREE); edge edge_true_true, edge_true_false, edge_false; if_then_if_then_else (g, g2, profile_probability::likely (), - profile_probability::likely (), + profile_probability::unlikely (), edge_true_true, edge_true_false, edge_false); tree l = limb_access (type, var ? var : obj, idx, true); @@ -4269,8 +4269,11 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt) if (!single_comparison) { m_gsi = gsi_after_labels (edge_true_true->src); - l = limb_access (type, var ? var : obj, - size_int (prec_limbs - 1), true); + tree plm1idx = size_int (prec_limbs - 1); + tree plm1type = limb_access_type (type, plm1idx); + l = limb_access (type, var ? var : obj, plm1idx, true); + if (!useless_type_conversion_p (plm1type, TREE_TYPE (rhs))) + rhs = add_cast (plm1type, rhs); if (!useless_type_conversion_p (TREE_TYPE (l), TREE_TYPE (rhs))) rhs = add_cast (TREE_TYPE (l), rhs); diff --git a/gcc/testsuite/gcc.dg/torture/bitint-60.c b/gcc/testsuite/gcc.dg/torture/bitint-60.c new file mode 100644 index 000000000000..d2d27a188b67 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/bitint-60.c @@ -0,0 +1,24 @@ +/* PR tree-optimization/114040 */ +/* { dg-do run { target bitint } } */ +/* { dg-options "-std=c23 -pedantic-errors" } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */ + +#if __BITINT_MAXWIDTH__ >= 8671 +__attribute__((noipa)) unsigned +foo (unsigned _BitInt(8671) x, unsigned y, unsigned _BitInt(512) z) +{ + unsigned _BitInt (8671) r + = x * __builtin_sub_overflow_p (y * z, 0, (unsigned _BitInt(255)) 0); + return r; +} +#endif + +int +main () +{ +#if __BITINT_MAXWIDTH__ >= 8671 + if (foo (1, 1, 0xfffa46471e7c2dd60000000000000000wb)) + __builtin_abort (); +#endif +} diff --git a/gcc/testsuite/gcc.dg/torture/bitint-61.c b/gcc/testsuite/gcc.dg/torture/bitint-61.c new file mode 100644 index 000000000000..e5651f10ea46 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/bitint-61.c @@ -0,0 +1,36 @@ +/* PR tree-optimization/114040 */ +/* { dg-do run { target { bitint && int128 } } } */ +/* { dg-options "-std=c23" } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */ +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */ + +unsigned a; +signed char b; +short c; +long d; +__int128 e; +int f; + +#if __BITINT_MAXWIDTH__ >= 511 +__attribute__((noinline)) void +foo (_BitInt(3) x, unsigned _BitInt(511) y, unsigned *z) +{ + int g = __builtin_sub_overflow_p (y ^ x, 0, (unsigned _BitInt(255)) 0); + unsigned h = y + e, i = h + d; + unsigned _BitInt(2) j = i + g; + unsigned k = j + c; + unsigned l = k + a + f + b; + *z = l; +} +#endif + +int +main () +{ +#if __BITINT_MAXWIDTH__ >= 511 + unsigned x; + foo (0, 0x81e4a5fa7c408f370000000000000000uwb, &x); + if (x) + __builtin_abort (); +#endif +}
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