Code hoisting part of GIMPLE PRE failed to adjust the TBAA behavior of common loads in the case the alias set of the ref was the same but the base alias set was not. It also failed to adjust the base behavior, assuming it would match. The following plugs this hole.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. PR tree-optimization/110799 * tree-ssa-pre.cc (compute_avail): More thoroughly match up TBAA behavior of redundant loads. * gcc.dg/torture/pr110799.c: New testcase. --- gcc/testsuite/gcc.dg/torture/pr110799.c | 46 +++++++++++++++++++++++++ gcc/tree-ssa-pre.cc | 15 +++++--- 2 files changed, 56 insertions(+), 5 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr110799.c diff --git a/gcc/testsuite/gcc.dg/torture/pr110799.c b/gcc/testsuite/gcc.dg/torture/pr110799.c new file mode 100644 index 00000000000..53f06f079e1 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr110799.c @@ -0,0 +1,46 @@ +/* { dg-do run { target { { *-*-linux* *-*-gnu* *-*-uclinux* } && mmap } } } */ + +#include <unistd.h> +#include <stdlib.h> +#include <sys/mman.h> + +struct S { + int a; +}; +struct M { + int a, b; +}; + +int __attribute__((noipa)) +f(struct S *p, int c, int d) +{ + int r; + if (c) + { + if (d) + r = p->a; + else + r = ((struct M*)p)->a; + } + else + r = ((struct M*)p)->b; + return r; +} + +int main () +{ + long pgsz = sysconf(_SC_PAGESIZE); + if (pgsz < sizeof (struct M)) + return 0; + char *p = mmap ((void *) 0, 2 * pgsz, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, + -1, 0); + if (p == MAP_FAILED) + return 0; + if (mprotect (p, pgsz, PROT_READ | PROT_WRITE)) + return 0; + struct S *q = (struct S *)(p + pgsz) - 1; + q->a = 42; + if (f (q, 1, 1) != 42) + abort (); + return 0; +} diff --git a/gcc/tree-ssa-pre.cc b/gcc/tree-ssa-pre.cc index e33c5ba80e2..0f2e458395c 100644 --- a/gcc/tree-ssa-pre.cc +++ b/gcc/tree-ssa-pre.cc @@ -4217,8 +4217,10 @@ compute_avail (function *fun) /* TBAA behavior is an obvious part so make sure that the hashtable one covers this as well by adjusting the ref alias set and its base. */ - if (ref->set == set - || alias_set_subset_of (set, ref->set)) + if ((ref->set == set + || alias_set_subset_of (set, ref->set)) + && (ref->base_set == base_set + || alias_set_subset_of (base_set, ref->base_set))) ; else if (ref1->opcode != ref2->opcode || (ref1->opcode != MEM_REF @@ -4230,16 +4232,19 @@ compute_avail (function *fun) operands.release (); continue; } - else if (alias_set_subset_of (ref->set, set)) + else if (ref->set == set + || alias_set_subset_of (ref->set, set)) { + tree reft = reference_alias_ptr_type (rhs1); ref->set = set; + ref->base_set = set; if (ref1->opcode == MEM_REF) ref1->op0 - = wide_int_to_tree (TREE_TYPE (ref2->op0), + = wide_int_to_tree (reft, wi::to_wide (ref1->op0)); else ref1->op2 - = wide_int_to_tree (TREE_TYPE (ref2->op2), + = wide_int_to_tree (reft, wi::to_wide (ref1->op2)); } else -- 2.35.3