Hi Suwa-san,
On Fri, Sep 2, 2022 at 3:57 AM Takayuki 'January June' Suwa
<[email protected]> wrote:
>
> Changes from v1:
> (xtensa_expand_epilogue): Fixed forgetting to consider
> hard_frame_pointer_rtx when sharing codes.
>
> ---
> In the example below, 'x' is once placed on the stack frame and then read
> into registers as the argument value of bar():
>
> /* example */
> struct foo {
> int a, b;
> };
> extern struct foo bar(struct foo);
> struct foo test(void) {
> struct foo x = { 0, 1 };
> return bar(x);
> }
>
> Thanks to the dead store elimination, the initialization of 'x' turns into
> merely loading the immediates to registers, but corresponding stack frame
> growth is not rolled back. As a result:
>
> ;; prereq: the CALL0 ABI
> ;; before
> test:
> addi sp, sp, -16 // unused stack frame allocation/freeing
> movi.n a2, 0
> movi.n a3, 1
> addi sp, sp, 16 // because no instructions that refer to
> j.l bar, a9 // the stack pointer between the two
>
> This patch eliminates such unused stack frame allocation/freeing:
>
> ;; after
> test:
> movi.n a2, 0
> movi.n a3, 1
> j.l bar, a9
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.cc (machine_function): New member to track
> the insns for stack pointer adjustment inside of the pro/epilogue.
> (xtensa_emit_adjust_stack_ptr): New function to share the common
> codes and to record the insns for stack pointer adjustment.
> (xtensa_expand_prologue): Change to use the function mentioned
> above when using the CALL0 ABI.
> (xtensa_expand_epilogue): Ditto.
> And also change to cancel emitting the insns for the stack pointer
> adjustment if only used for its own.
> ---
> gcc/config/xtensa/xtensa.cc | 230 ++++++++++++++++++------------------
> 1 file changed, 118 insertions(+), 112 deletions(-)
With this change xtensa-linux-uclibc configured for call0 ABI
produces ICE while building libgcc:
gcc/libgcc/libgcc2.c: In function ‘__divdi3’:
gcc/libgcc/libgcc2.c:1230:1: internal compiler error: Segmentation fault
1230 | }
| ^
0xea801f crash_signal
gcc/gcc/toplev.cc:314
0x7f1fb4be5d5f ???
./signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
0x9602e3 lookup_page_table_entry
gcc/gcc/ggc-page.cc:630
0x9602e3 ggc_set_mark(void const*)
gcc/gcc/ggc-page.cc:1550
0x121d7bd gt_ggc_mx_hash_set_rtx_insn__(void*)
./gt-xtensa.h:38
0xbe6187 gt_ggc_mx_function(void*)
gcc-13-2434-g2f4d626e13dc-call0-le/gcc/gtype-desc.cc:1694
0xbe6187 gt_ggc_mx_function(void*)
gcc-13-2434-g2f4d626e13dc-call0-le/gcc/gtype-desc.cc:1678
0x85634a gt_ggc_mx_lang_tree_node(void*)
./gt-c-c-decl.h:289
0xbe07d2 gt_ggc_mx_rtx_def(void*)
gcc-13-2434-g2f4d626e13dc-call0-le/gcc/gtype-desc.cc:725
0xa47074 void gt_ggc_mx<dw_attr_struct>(vec<dw_attr_struct, va_gc, vl_embed>*)
gcc/gcc/vec.h:1363
0xa47074 gt_ggc_mx_vec_dw_attr_node_va_gc_(void*)
./gt-dwarf2out.h:261
0xa47074 gt_ggc_mx_vec_dw_attr_node_va_gc_(void*)
./gt-dwarf2out.h:256
0xa47074 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:45
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:27
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:47
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:27
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:47
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:27
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:47
0xa470d7 gt_ggc_mx_die_struct(void*)
./gt-dwarf2out.h:27
--
Thanks.
-- Max
