On Tue, Jan 16, 2024 at 9:26 PM Qing Zhao <qing.z...@oracle.com> wrote: > > > > > On Jan 15, 2024, at 4:31 AM, Richard Biener <richard.guent...@gmail.com> > > wrote: > > > >> All my questions for unshare_expr relate to a LTO bug that I currently > >> stuck with > >> when using .ACCESS_WITH_SIZE in bound sanitizer (only with -flto, without > >> -flto, no issue): > >> > >> [opc@qinzhao-aarch64-ol8 gcc]$ sh t > >> during IPA pass: modref > >> t.c:20:1: internal compiler error: tree code ‘ssa_name’ is not supported > >> in LTO streams > >> 0x14c3993 lto_write_tree > >> ../../latest-gcc-write/gcc/lto-streamer-out.cc:561 > >> 0x14c3aeb lto_output_tree_1 > >> > >> And the value of the tree node that triggered the ICE is: > >> (gdb) call debug_tree(expr) > >> <ssa_name 0xfffff5761e60 type <error_mark 0xfffff56c0e58> > >> nothrow > >> def_stmt > >> version:13 in-free-list> > >> > >> Is there any good way to debug LTO bug? > > > > This happens usually when you have a VLA type and its type fields are not > > properly gimplified which usually happens because the frontend fails to > > insert a gimplification point for it (a DECL_EXPR). > > I found an old gcc bug > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97172 > ICE: tree code ‘ssa_name’ is not supported in LTO streams since > r11-3303-g6450f07388f9fe57 > > Which is very similar to the bug I am having right now. > > After further study, I suspect that the issue I am having right now with the > LTO streaming also > relate to “unshare_expr”, “save_expr”, and the combination of these two, I > suspect that > the current gcc cannot handle the combination of these two correctly for my > case. > > My testing case is: > > #include <stdlib.h> > void __attribute__((__noinline__)) setup_and_test_vla (int n1, int n2, int m) > { > struct foo { > int n; > int p[][n2][n1] __attribute__((counted_by(n))); > } *f; > > f = (struct foo *) malloc (sizeof(struct foo) + m*sizeof(int[n2][n1])); > f->n = m; > f->p[m][n2][n1]=1; > return; > } > > int main(int argc, char *argv[]) > { > setup_and_test_vla (10, 11, 20); > return 0; > } > > Failed with > my_gcc -Os -fsanitize=bounds -flto > > If changing either n1 or n2 to a constant, the testing passed. > If deleting -flto, the testing passed too. > > I double checked my code per the suggestions provided by you and Jakub in this > email thread, and I think the code should be fine. > > The code is following: > > ===== > 504 /* Instrument array bounds for INDIRECT_REFs whose pointers are > 505 POINTER_PLUS_EXPRs of calls to .ACCESS_WITH_SIZE. We create special > 506 builtins that gets expanded in the sanopt pass, and make an array > 507 dimension of it. ARRAY is the pointer to the base of the array, > 508 which is a call to .ACCESS_WITH_SIZE, *OFFSET is the offset to the > 509 beginning of array. > 510 Return NULL_TREE if no instrumentation is emitted. */ > 511 > 512 tree > 513 ubsan_instrument_bounds_indirect_ref (location_t loc, tree array, tree > *offset) > 514 { > 515 if (!is_access_with_size_p (array)) > 516 return NULL_TREE; > 517 tree bound = get_bound_from_access_with_size (array); > 518 /* The type of the call to .ACCESS_WITH_SIZE is a pointer type to > 519 the element of the array. */ > 520 tree element_size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (array))); > 521 gcc_assert (bound); > 522 > 523 /* Given the offset, and the size of each element, the index can be > 524 computed as: offset/element_size. */ > 525 *offset = save_expr (*offset); > 526 tree index = fold_build2 (EXACT_DIV_EXPR, > 527 sizetype, *offset, > 528 unshare_expr (element_size)); > 529 /* Create a "(T *) 0" tree node to describe the original array type. > 530 We get the original array type from the first argument of the call to > 531 .ACCESS_WITH_SIZE (REF, COUNTED_BY_REF, 1, num_bytes, -1). > 532 > 533 Originally, REF is a COMPONENT_REF with the original array type, > 534 it was converted to a pointer to an ADDR_EXPR, and the ADDR_EXPR's > 535 first operand is the original COMPONENT_REF. */ > 536 tree ref = CALL_EXPR_ARG (array, 0); > 537 tree array_type > 538 = unshare_expr (TREE_TYPE (TREE_OPERAND (TREE_OPERAND(ref, 0), 0))); > 539 tree zero_with_type = build_int_cst (build_pointer_type (array_type), > 0); > 540 return build_call_expr_internal_loc (loc, IFN_UBSAN_BOUNDS, > 541 void_type_node, 3, zero_with_type, > 542 index, bound); > 543 } > > ===== > > Inside gdb, the guilty IR failed in LTO streaming is from the above line 520: > TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (array))), > > When I use this tree node as an operand of the expression at line 526, I added > unshare_expr. > > However, I still see the guilty IR as in gdb: > > unit-size <mult_expr 0xfffff5aabf90 type <integer_type > 0xfffff57c0000 sizetype> > side-effects > arg:0 <mult_expr 0xfffff5aabf68 type <integer_type > 0xfffff57c0000 sizetype> > > arg:0 <ssa_name 0xfffff5761e18 type <error_mark > 0xfffff56c0e58> > nothrow > def_stmt > version:12 in-free-list> > arg:1 <ssa_name 0xfffff5761e60 type <error_mark > 0xfffff56c0e58> > nothrow > def_stmt > version:13 in-free-list>> > arg:1 <integer_cst 0xfffff56c10c8 constant 4>> > > > I have been stuck with this bug for quite some time. > Any help is helpful.
The above hasn't been gimplified correctly, you'd instead see a D.1234 in there, not an expression with SSA names. That happens when the frontend fails to emit a DECL_EXPR for a decl with this type. > > Qing > > > > >> Thanks a lot for the help. > >> > >> Qing > >> >
