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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2560] tree-optimization/106722 - avoid invalid pointer association in predcom Date: Fri, 9 Sep 2022 12:32:35 +0000 (GMT) [thread overview] Message-ID: <20220909123235.DB51C38582BF@sourceware.org> (raw) https://gcc.gnu.org/g:a8b0b13da7379feb31950a9d2ad74b98a29c547f commit r13-2560-ga8b0b13da7379feb31950a9d2ad74b98a29c547f Author: Richard Biener <rguenther@suse.de> Date: Fri Sep 9 12:06:38 2022 +0200 tree-optimization/106722 - avoid invalid pointer association in predcom When predictive commoning builds a reference for iteration N it prematurely associates a constant offset into the MEM_REF offset operand which can be invalid if the base pointer then points outside of an object which alias-analysis does not consider valid. PR tree-optimization/106722 * tree-predcom.cc (ref_at_iteration): Do not associate the constant part of the offset into the MEM_REF offset operand, across a non-zero offset. * gcc.dg/torture/pr106892.c: New testcase. Diff: --- gcc/testsuite/gcc.dg/torture/pr106892.c | 30 ++++++++++++++++++++++++++++++ gcc/tree-predcom.cc | 18 ++++++++++++++++-- 2 files changed, 46 insertions(+), 2 deletions(-) diff --git a/gcc/testsuite/gcc.dg/torture/pr106892.c b/gcc/testsuite/gcc.dg/torture/pr106892.c new file mode 100644 index 00000000000..73a66a037b7 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr106892.c @@ -0,0 +1,30 @@ +/* { dg-do run } */ + +int a, b, c, d, e; +int f[8]; +static int g() { + while (a) + a >>= 4; + return 0; +} +static int h(int i) { + if (i >= '0') + return i - '0'; + //__builtin_unreachable (); +} +void __attribute__((noipa)) j(int i) { + for (b = 2; g() <= 7; b++) + if (i) { + for (; e <= 7; e++) + for (c = 1; c <= 7; c++) { + d = h(b + '0'); + f[-d + 4] ^= 3; + } + return; + } +} +int main() { + j(1); + if (f[2] != 0) + __builtin_abort (); +} diff --git a/gcc/tree-predcom.cc b/gcc/tree-predcom.cc index 5d923fba170..a6e45e36ffd 100644 --- a/gcc/tree-predcom.cc +++ b/gcc/tree-predcom.cc @@ -1771,10 +1771,24 @@ ref_at_iteration (data_reference_p dr, int iter, ref = TREE_OPERAND (ref, 0); } } - tree addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off); + /* We may not associate the constant offset across the pointer plus + expression because that might form a pointer to before the object + then. But for some cases we can retain that to allow tree_could_trap_p + to return false - see gcc.dg/tree-ssa/predcom-1.c */ + tree addr, alias_ptr; + if (integer_zerop (off)) + { + alias_ptr = fold_convert (reference_alias_ptr_type (ref), coff); + addr = DR_BASE_ADDRESS (dr); + } + else + { + alias_ptr = build_zero_cst (reference_alias_ptr_type (ref)); + off = size_binop (PLUS_EXPR, off, coff); + addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off); + } addr = force_gimple_operand_1 (unshare_expr (addr), stmts, is_gimple_mem_ref_addr, NULL_TREE); - tree alias_ptr = fold_convert (reference_alias_ptr_type (ref), coff); tree type = build_aligned_type (TREE_TYPE (ref), get_object_alignment (ref)); ref = build2 (MEM_REF, type, addr, alias_ptr);
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