On Fri, 3 May 2024, Jakub Jelinek wrote:
> Hi!
>
> The following patch adds save_NNN = __builtin_stack_save (); ...
> __builtin_stack_restore (save_NNN);
> pair around inline calls which call alloca (alloca calls because of
> VLA vars are ignored in that decision).
> The patch doesn't change anything on whether we try to inline such calls or
> not, it just fixes the behavior when we inline them despite those checks.
> The stack save/restore restores the behavior that alloca acquired regions
> are freed at the end of the containing call.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2024-05-03 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/113596
> * tree-inline.cc (expand_call_inline): Emit __builtin_stack_save
> and __builtin_stack_restore calls around inlined functions which
> call alloca.
>
> * gcc.dg/pr113596.c: New test.
> * gcc.dg/tree-ssa/pr113596.c: New test.
>
> --- gcc/tree-inline.cc.jj 2024-04-11 11:09:07.274670922 +0200
> +++ gcc/tree-inline.cc 2024-05-02 19:05:06.963750322 +0200
> @@ -4794,6 +4794,7 @@ expand_call_inline (basic_block bb, gimp
> use_operand_p use;
> gimple *simtenter_stmt = NULL;
> vec<tree> *simtvars_save;
> + tree save_stack = NULL_TREE;
>
> /* The gimplifier uses input_location in too many places, such as
> internal_get_tmp_var (). */
> @@ -5042,6 +5043,28 @@ expand_call_inline (basic_block bb, gimp
> GSI_NEW_STMT);
> }
>
> + /* If function to be inlined calls alloca, wrap the inlined function
> + in between save_stack = __builtin_stack_save (); and
> + __builtin_stack_restore (save_stack); calls. */
> + if (id->src_cfun->calls_alloca && !gimple_call_noreturn_p (stmt))
> + /* Don't do this for VLA allocations though, just for user alloca
> + calls. */
> + for (struct cgraph_edge *e = id->src_node->callees; e; e =
> e->next_callee)
> + if (gimple_maybe_alloca_call_p (e->call_stmt)
> + && !gimple_call_alloca_for_var_p (e->call_stmt))
> + {
> + tree fn = builtin_decl_implicit (BUILT_IN_STACK_SAVE);
> + gcall *call = gimple_build_call (fn, 0);
> + save_stack = make_ssa_name (ptr_type_node);
> + gimple_call_set_lhs (call, save_stack);
> + gimple_stmt_iterator si = gsi_last_bb (bb);
> + gsi_insert_after (&si, call, GSI_NEW_STMT);
> + struct cgraph_node *dest = cgraph_node::get_create (fn);
> + id->dst_node->create_edge (dest, call, bb->count)->inline_failed
> + = CIF_BODY_NOT_AVAILABLE;
> + break;
> + }
> +
> if (DECL_INITIAL (fn))
> {
> if (gimple_block (stmt))
> @@ -5165,6 +5188,17 @@ expand_call_inline (basic_block bb, gimp
> }
> }
>
> + if (save_stack)
> + {
> + tree fn = builtin_decl_implicit (BUILT_IN_STACK_RESTORE);
> + gcall *call = gimple_build_call (fn, 1, save_stack);
> + gsi_insert_before (&stmt_gsi, call, GSI_SAME_STMT);
> + struct cgraph_node *dest = cgraph_node::get_create (fn);
> + id->dst_node->create_edge (dest, call,
> + return_block->count)->inline_failed
> + = CIF_BODY_NOT_AVAILABLE;
> + }
> +
> /* Reset the escaped solution. */
> if (cfun->gimple_df)
> {
> --- gcc/testsuite/gcc.dg/pr113596.c.jj 2024-05-02 15:05:25.048642302
> +0200
> +++ gcc/testsuite/gcc.dg/pr113596.c 2024-05-02 15:05:25.048642302 +0200
> @@ -0,0 +1,24 @@
> +/* PR middle-end/113596 */
> +/* { dg-do run } */
> +/* { dg-options "-O2" } */
> +
> +__attribute__((noipa)) void
> +bar (char *p, int n)
> +{
> + p[0] = 1;
> + p[n - 1] = 2;
> +}
> +
> +static inline __attribute__((always_inline)) void
> +foo (int n)
> +{
> + char *p = __builtin_alloca (n);
> + bar (p, n);
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 2; i < 8192; ++i)
> + foo (i);
> +}
> --- gcc/testsuite/gcc.dg/tree-ssa/pr113596.c.jj 2024-05-02
> 19:10:29.218455257 +0200
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr113596.c 2024-05-02 19:11:11.211895559
> +0200
> @@ -0,0 +1,37 @@
> +/* PR middle-end/113596 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-einline" } */
> +/* { dg-final { scan-tree-dump-times "__builtin_stack_save \\\(" 3 "einline"
> } } */
> +/* { dg-final { scan-tree-dump-times "__builtin_stack_restore \\\(" 3
> "einline" } } */
> +
> +void baz (char *p, int n);
> +volatile int v;
> +
> +static inline __attribute__((always_inline)) void
> +foo (int n)
> +{
> + ++v;
> + {
> + char *p = __builtin_alloca (n);
> + baz (p, n);
> + }
> + ++v;
> +}
> +
> +static inline __attribute__((always_inline)) void
> +bar (int n)
> +{
> + ++v;
> + {
> + char p[n];
> + baz (p, n);
> + }
> + ++v;
> +}
> +
> +void
> +qux (int n)
> +{
> + foo (n);
> + bar (n);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
