From 1a78fffb3845f879e36ba33b4d15e75b3df8d5a7 Mon Sep 17 00:00:00 2001 From: Martin Jambor Date: Mon, 11 Jul 2022 18:43:23 +0200 Subject: [PATCH] tree-sra: Fix union handling in build_reconstructed_reference As the testcase in PR 105860 shows, the code that tries to re-use the handled_component chains in SRA can be horribly confused by unions, where it thinks it has found a compatible structure under which it can chain the references, but in fact it found the type it was looking for elsewhere in a union and generated a write to a completely wrong part of an aggregate. I don't remember whether the plan was to support unions at all in build_reconstructed_reference but it can work, to an extent, if we make sure that we start the search only outside the outermost union, which is what the patch does (and the extra testcase verifies). Additionally, this commit also contains sqashed in it a backport of b984b84cbe4bf026edef2ba37685f3958a1dc1cf which fixes the testcase gcc.dg/tree-ssa/alias-access-path-13.c for many 32-bit targets. gcc/ChangeLog: 2022-07-01 Martin Jambor PR tree-optimization/105860 * tree-sra.cc (build_reconstructed_reference): Start expr traversal only just below the outermost union. gcc/testsuite/ChangeLog: 2022-07-01 Martin Jambor PR tree-optimization/105860 * gcc.dg/tree-ssa/alias-access-path-13.c: New test. * gcc.dg/tree-ssa/pr105860.c: Likewise. (cherry picked from commit b110e5283e368b5377e04766e4ff82cd52634208) --- .../gcc.dg/tree-ssa/alias-access-path-13.c | 36 +++++++++++++ gcc/testsuite/gcc.dg/tree-ssa/pr105860.c | 63 ++++++++++++++++++++++ gcc/tree-sra.cc | 13 ++++- 3 files changed, 111 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/alias-access-path-13.c create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr105860.c diff --git a/gcc/testsuite/gcc.dg/tree-ssa/alias-access-path-13.c b/gcc/testsuite/gcc.dg/tree-ssa/alias-access-path-13.c new file mode 100644 index 0000000..87a94f5 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/alias-access-path-13.c @@ -0,0 +1,36 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-fre1" } */ + +struct inn +{ + int val; +}; + +struct biggerstruct +{ + int a, b; +}; + +union foo +{ + struct inn inn; + struct biggerstruct baz; +} *fooptr; + +struct bar +{ + union foo foo; + int val2; +} *barptr; + +int +test () +{ + union foo foo; + foo.inn.val = 0; + barptr->val2 = 123; + *fooptr = foo; + return barptr->val2; +} + +/* { dg-final { scan-tree-dump-times "return 123" 1 "fre1"} } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr105860.c b/gcc/testsuite/gcc.dg/tree-ssa/pr105860.c new file mode 100644 index 0000000..77bcb4a --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr105860.c @@ -0,0 +1,63 @@ +/* { dg-do run } */ +/* { dg-options "-O1" } */ + +struct S1 { + unsigned int _0; + unsigned int _1; +} ; +struct S2 { + struct S1 _s1; + unsigned long _x2; +} ; + +struct ufld_type1 { + unsigned int _u1t; + struct S2 _s2; +} ; + +struct ufld_type2 { + unsigned int _u2t; + struct S1 _s1; +} ; +struct parm_type { + union { + struct ufld_type1 var_1; + struct ufld_type2 var_2; + } U; +}; + +struct parm_type bad_function( struct parm_type arg0 ) +{ + struct parm_type rv; + struct S2 var4; + switch( arg0.U.var_2._u2t ) { + case 4294967041: + var4._s1 = arg0.U.var_1._s2._s1; + rv.U.var_1._u1t = 4294967041; + rv.U.var_1._s2 = var4; + break; + case 4294967043: + rv.U.var_2._u2t = 4294967043; + rv.U.var_2._s1 = arg0.U.var_2._s1; + break; + default: + break; + } + return rv; +} + +int main() { + struct parm_type val; + struct parm_type out; + val.U.var_2._u2t = 4294967043; + val.U.var_2._s1._0 = 0x01010101; + val.U.var_2._s1._1 = 0x02020202; + out = bad_function(val); + if (val.U.var_2._u2t != 4294967043) + __builtin_abort (); + if (out.U.var_2._s1._0 != 0x01010101) + __builtin_abort (); + if (val.U.var_2._s1._1 != 0x02020202 ) + __builtin_abort (); + return 0; +} diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc index 081c51b..099e8db 100644 --- a/gcc/tree-sra.cc +++ b/gcc/tree-sra.cc @@ -1667,7 +1667,18 @@ build_ref_for_offset (location_t loc, tree base, poly_int64 offset, static tree build_reconstructed_reference (location_t, tree base, struct access *model) { - tree expr = model->expr, prev_expr = NULL; + tree expr = model->expr; + /* We have to make sure to start just below the outermost union. */ + tree start_expr = expr; + while (handled_component_p (expr)) + { + if (TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == UNION_TYPE) + start_expr = expr; + expr = TREE_OPERAND (expr, 0); + } + + expr = start_expr; + tree prev_expr = NULL_TREE; while (!types_compatible_p (TREE_TYPE (expr), TREE_TYPE (base))) { if (!handled_component_p (expr)) -- 2.7.4