From 9e72a522dd9f835dd159fe3aff493eee001be0d4 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Tue, 21 Jun 2022 11:40:16 +0200 Subject: [PATCH] ifcvt: Don't introduce trapping or faulting reads in noce_try_sign_mask [PR106032] noce_try_sign_mask as documented will optimize if (c < 0) x = t; else x = 0; into x = (c >> bitsm1) & t; The optimization is done if either t is unconditional (e.g. for x = t; if (c >= 0) x = 0; ) or if it is cheap. We already check that t doesn't have side-effects, but if t is conditional, we need to punt also if it may trap or fault, as we make it unconditional. I've briefly skimmed other noce_try* optimizations and didn't find one that would suffer from the same problem. 2022-06-21 Jakub Jelinek PR rtl-optimization/106032 * ifcvt.cc (noce_try_sign_mask): Punt if !t_unconditional, and t may_trap_or_fault_p, even if it is cheap. * gcc.c-torture/execute/pr106032.c: New test. (cherry picked from commit a0c30fe3b888f20215f3e040d21b62b603804ca9) --- gcc/ifcvt.cc | 15 ++++++++------- gcc/testsuite/gcc.c-torture/execute/pr106032.c | 21 +++++++++++++++++++++ 2 files changed, 29 insertions(+), 7 deletions(-) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr106032.c diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc index b983e87..e007b17 100644 --- a/gcc/ifcvt.cc +++ b/gcc/ifcvt.cc @@ -2833,18 +2833,19 @@ noce_try_sign_mask (struct noce_if_info *if_info) return FALSE; /* This is only profitable if T is unconditionally executed/evaluated in the - original insn sequence or T is cheap. The former happens if B is the - non-zero (T) value and if INSN_B was taken from TEST_BB, or there was no - INSN_B which can happen for e.g. conditional stores to memory. For the - cost computation use the block TEST_BB where the evaluation will end up - after the transformation. */ + original insn sequence or T is cheap and can't trap or fault. The former + happens if B is the non-zero (T) value and if INSN_B was taken from + TEST_BB, or there was no INSN_B which can happen for e.g. conditional + stores to memory. For the cost computation use the block TEST_BB where + the evaluation will end up after the transformation. */ t_unconditional = (t == if_info->b && (if_info->insn_b == NULL_RTX || BLOCK_FOR_INSN (if_info->insn_b) == if_info->test_bb)); if (!(t_unconditional - || (set_src_cost (t, mode, if_info->speed_p) - < COSTS_N_INSNS (2)))) + || ((set_src_cost (t, mode, if_info->speed_p) + < COSTS_N_INSNS (2)) + && !may_trap_or_fault_p (t)))) return FALSE; if (!noce_can_force_operand (t)) diff --git a/gcc/testsuite/gcc.c-torture/execute/pr106032.c b/gcc/testsuite/gcc.c-torture/execute/pr106032.c new file mode 100644 index 0000000..d2ccf6a5 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr106032.c @@ -0,0 +1,21 @@ +/* PR rtl-optimization/106032 */ + +__attribute__((noipa)) int +foo (int x, int *y) +{ + int a = 0; + if (x < 0) + a = *y; + return a; +} + +int +main () +{ + int a = 42; + if (foo (0, 0) != 0 || foo (1, 0) != 0) + __builtin_abort (); + if (foo (-1, &a) != 42 || foo (-42, &a) != 42) + __builtin_abort (); + return 0; +} -- 2.7.4