* [PATCH v2 #1/2] enable adjustment of return_pc debug attrs
@ 2023-03-23 3:12 Alexandre Oliva, Alexandre Oliva
2023-03-23 3:15 ` [PATCH v2 #2/2] [rs6000] adjust " Alexandre Oliva
2023-04-14 14:12 ` [PATCH v2 #1/2] enable adjustment of " Alexandre Oliva
0 siblings, 2 replies; 4+ messages in thread
From: Alexandre Oliva, Alexandre Oliva @ 2023-03-23 3:12 UTC (permalink / raw)
To: gcc-patches; +Cc: Tom Tromey, Jason Merrill, Cary Coutant, Jakub Jelinek
This patch introduces infrastructure for targets to add an offset to
the label issued after the call_insn to set the call_return_pc
attribute. This will be used on rs6000, that sometimes issues another
instruction after the call proper as part of a call insn.
Regstrapped on x86_64-linux-gnu and ppc64-linux-gnu. Ok to install?
for gcc/ChangeLog
* target.def (call_offset_return_label): New hook.
* gcc/doc/tm.texi.in (TARGET_CALL_OFFSET_RETURN_LABEL): Add
placeholder.
* gcc/doc/tm.texi: Rebuild.
* dwarf2out.cc (struct call_arg_loc_node): Record call_insn
instad of call_arg_loc_note.
(add_AT_lbl_id): Add optional offset argument.
(gen_call_site_die): Compute and pass on a return pc offset.
(gen_subprogram_die): Move call_arg_loc_note computation...
(dwarf2out_var_location): ... from here. Set call_insn.
---
gcc/doc/tm.texi | 7 +++++++
gcc/doc/tm.texi.in | 2 ++
gcc/dwarf2out.cc | 26 +++++++++++++++++---------
gcc/target.def | 9 +++++++++
4 files changed, 35 insertions(+), 9 deletions(-)
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index c4a92a5ebee90..44e4c18ad5c0a 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -5426,6 +5426,13 @@ except the last are treated as named.
You need not define this hook if it always returns @code{false}.
@end deftypefn
+@deftypefn {Target Hook} int TARGET_CALL_OFFSET_RETURN_LABEL (rtx_insn *@var{call_insn})
+While generating call-site debug info for a CALL insn, or a SEQUENCE
+insn starting with a CALL, this target hook is invoked to compute the
+offset to be added to the debug label emitted after the call to obtain
+the return address that should be recorded as the return PC.
+@end deftypefn
+
@deftypefn {Target Hook} void TARGET_CALL_ARGS (rtx, @var{tree})
While generating RTL for a function call, this target hook is invoked once
for each argument passed to the function, either a register returned by
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 4075e71624c04..68856978fe364 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -3785,6 +3785,8 @@ These machine description macros help implement varargs:
@hook TARGET_STRICT_ARGUMENT_NAMING
+@hook TARGET_CALL_OFFSET_RETURN_LABEL
+
@hook TARGET_CALL_ARGS
@hook TARGET_END_CALL_ARGS
diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 1711ad2c2da31..d1db918c43900 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -3584,7 +3584,7 @@ typedef struct var_loc_list_def var_loc_list;
/* Call argument location list. */
struct GTY ((chain_next ("%h.next"))) call_arg_loc_node {
- rtx GTY (()) call_arg_loc_note;
+ rtx_insn * GTY (()) call_insn;
const char * GTY (()) label;
tree GTY (()) block;
bool tail_call_p;
@@ -3768,7 +3768,8 @@ static void remove_addr_table_entry (addr_table_entry *);
static void add_AT_addr (dw_die_ref, enum dwarf_attribute, rtx, bool);
static inline rtx AT_addr (dw_attr_node *);
static void add_AT_symview (dw_die_ref, enum dwarf_attribute, const char *);
-static void add_AT_lbl_id (dw_die_ref, enum dwarf_attribute, const char *);
+static void add_AT_lbl_id (dw_die_ref, enum dwarf_attribute, const char *,
+ int = 0);
static void add_AT_lineptr (dw_die_ref, enum dwarf_attribute, const char *);
static void add_AT_macptr (dw_die_ref, enum dwarf_attribute, const char *);
static void add_AT_range_list (dw_die_ref, enum dwarf_attribute,
@@ -5327,14 +5328,17 @@ add_AT_symview (dw_die_ref die, enum dwarf_attribute attr_kind,
static inline void
add_AT_lbl_id (dw_die_ref die, enum dwarf_attribute attr_kind,
- const char *lbl_id)
+ const char *lbl_id, int offset)
{
dw_attr_node attr;
attr.dw_attr = attr_kind;
attr.dw_attr_val.val_class = dw_val_class_lbl_id;
attr.dw_attr_val.val_entry = NULL;
- attr.dw_attr_val.v.val_lbl_id = xstrdup (lbl_id);
+ if (!offset)
+ attr.dw_attr_val.v.val_lbl_id = xstrdup (lbl_id);
+ else
+ attr.dw_attr_val.v.val_lbl_id = xasprintf ("%s%+i", lbl_id, offset);
if (dwarf_split_debug_info)
attr.dw_attr_val.val_entry
= add_addr_table_entry (attr.dw_attr_val.v.val_lbl_id,
@@ -23405,7 +23409,9 @@ gen_call_site_die (tree decl, dw_die_ref subr_die,
if (stmt_die == NULL)
stmt_die = subr_die;
die = new_die (dwarf_TAG (DW_TAG_call_site), stmt_die, NULL_TREE);
- add_AT_lbl_id (die, dwarf_AT (DW_AT_call_return_pc), ca_loc->label);
+ add_AT_lbl_id (die, dwarf_AT (DW_AT_call_return_pc),
+ ca_loc->label,
+ targetm.calls.call_offset_return_label (ca_loc->call_insn));
if (ca_loc->tail_call_p)
add_AT_flag (die, dwarf_AT (DW_AT_call_tail_call), 1);
if (ca_loc->symbol_ref)
@@ -24092,11 +24098,14 @@ gen_subprogram_die (tree decl, dw_die_ref context_die)
{
dw_die_ref die = NULL;
rtx tloc = NULL_RTX, tlocc = NULL_RTX;
+ rtx call_arg_loc_note
+ = find_reg_note (ca_loc->call_insn,
+ REG_CALL_ARG_LOCATION, NULL_RTX);
rtx arg, next_arg;
tree arg_decl = NULL_TREE;
- for (arg = (ca_loc->call_arg_loc_note != NULL_RTX
- ? XEXP (ca_loc->call_arg_loc_note, 0)
+ for (arg = (call_arg_loc_note != NULL_RTX
+ ? XEXP (call_arg_loc_note, 0)
: NULL_RTX);
arg; arg = next_arg)
{
@@ -28125,8 +28134,7 @@ create_label:
= ggc_cleared_alloc<call_arg_loc_node> ();
rtx_insn *prev = call_insn;
- ca_loc->call_arg_loc_note
- = find_reg_note (call_insn, REG_CALL_ARG_LOCATION, NULL_RTX);
+ ca_loc->call_insn = call_insn;
ca_loc->next = NULL;
ca_loc->label = last_label;
gcc_assert (prev
diff --git a/gcc/target.def b/gcc/target.def
index f401fe148ee2d..94c0e22819687 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -4731,6 +4731,15 @@ not generate any instructions in this case.",
int *pretend_args_size, int second_time),
default_setup_incoming_varargs)
+DEFHOOK
+(call_offset_return_label,
+ "While generating call-site debug info for a CALL insn, or a SEQUENCE\n\
+insn starting with a CALL, this target hook is invoked to compute the\n\
+offset to be added to the debug label emitted after the call to obtain\n\
+the return address that should be recorded as the return PC.",
+ int, (rtx_insn *call_insn),
+ hook_int_rtx_insn_0)
+
DEFHOOK
(call_args,
"While generating RTL for a function call, this target hook is invoked once\n\
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2 #2/2] [rs6000] adjust return_pc debug attrs
2023-03-23 3:12 [PATCH v2 #1/2] enable adjustment of return_pc debug attrs Alexandre Oliva, Alexandre Oliva
@ 2023-03-23 3:15 ` Alexandre Oliva
2023-04-14 14:12 ` [PATCH v2 #1/2] enable adjustment of " Alexandre Oliva
1 sibling, 0 replies; 4+ messages in thread
From: Alexandre Oliva @ 2023-03-23 3:15 UTC (permalink / raw)
To: gcc-patches; +Cc: Tom Tromey, David Edelsohn, Segher Boessenkool, Kewen Lin
Some of the rs6000 call patterns, on some ABIs, issue multiple opcodes
out of a single call insn, but the call (bl) or jump (b) is not always
the last opcode in the sequence.
This does not seem to be a problem for exception handling tables, but
the return_pc attribute in the call graph output in dwarf2+ debug
information, that takes the address of a label output right after the
call, does not match the value of the link register even for non-tail
calls. E.g., with ABI_AIX or ABI_ELFv2, such code as:
foo ();
outputs:
bl foo
nop
LVL#:
[...]
.8byte .LVL# # DW_AT_call_return_pc
but debug info consumers may rely on the return_pc address, and draw
incorrect conclusions from its off-by-4 value.
This patch uses the infrastructure for targets to add an offset to the
label issued after the call_insn to set the call_return_pc attribute,
on rs6000, to account for opcodes issued after actual call opcode as
part of call insns output patterns.
Regstrapped on x86_64-linux-gnu and ppc64-linux-gnu. Ok to install?
for gcc/ChangeLog
* config/rs6000/rs6000.cc (TARGET_CALL_OFFSET_RETURN_LABEL):
Override.
(rs6000_call_offset_return_label): New.
---
gcc/config/rs6000/rs6000.cc | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 8e0b0d022db2f..e55117159b270 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -1760,6 +1760,9 @@ static const struct attribute_spec rs6000_attribute_table[] =
#undef TARGET_UPDATE_IPA_FN_TARGET_INFO
#define TARGET_UPDATE_IPA_FN_TARGET_INFO rs6000_update_ipa_fn_target_info
+
+#undef TARGET_CALL_OFFSET_RETURN_LABEL
+#define TARGET_CALL_OFFSET_RETURN_LABEL rs6000_call_offset_return_label
\f
/* Processor table. */
@@ -14593,6 +14596,22 @@ rs6000_assemble_integer (rtx x, unsigned int size, int aligned_p)
return default_assemble_integer (x, size, aligned_p);
}
+/* Return the offset to be added to the label output after CALL_INSN
+ to compute the address to be placed in DW_AT_call_return_pc. */
+
+static int
+rs6000_call_offset_return_label (rtx_insn *call_insn)
+{
+ /* All rs6000 CALL_INSN output patterns start with a b or bl, always
+ a 4-byte instruction, but some output patterns issue other
+ opcodes afterwards. The return label is issued after the entire
+ call insn, including any such post-call opcodes. Instead of
+ figuring out which cases need adjustments, we compute the offset
+ back to the address of the call opcode proper, then add the
+ constant 4 bytes, to get the address after that opcode. */
+ return 4 - get_attr_length (call_insn);
+}
+
/* Return a template string for assembly to emit when making an
external call. FUNOP is the call mem argument operand number. */
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 #1/2] enable adjustment of return_pc debug attrs
2023-03-23 3:12 [PATCH v2 #1/2] enable adjustment of return_pc debug attrs Alexandre Oliva, Alexandre Oliva
2023-03-23 3:15 ` [PATCH v2 #2/2] [rs6000] adjust " Alexandre Oliva
@ 2023-04-14 14:12 ` Alexandre Oliva
2023-04-27 9:40 ` Alexandre Oliva
1 sibling, 1 reply; 4+ messages in thread
From: Alexandre Oliva @ 2023-04-14 14:12 UTC (permalink / raw)
To: gcc-patches
Cc: Tom Tromey, Jason Merrill, Cary Coutant, Jakub Jelinek,
David Edelsohn, Segher Boessenkool, Kewen Lin
On Mar 23, 2023, Alexandre Oliva <oliva@adacore.com> wrote:
> This patch introduces infrastructure for targets to add an offset to
> the label issued after the call_insn to set the call_return_pc
> attribute. This will be used on rs6000, that sometimes issues another
> instruction after the call proper as part of a call insn.
Ping?
https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614452.html
https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614453.html
This is a new feature, but it's needed to avoid regressions with the
recently-released GDB on ppc64.
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 #1/2] enable adjustment of return_pc debug attrs
2023-04-14 14:12 ` [PATCH v2 #1/2] enable adjustment of " Alexandre Oliva
@ 2023-04-27 9:40 ` Alexandre Oliva
0 siblings, 0 replies; 4+ messages in thread
From: Alexandre Oliva @ 2023-04-27 9:40 UTC (permalink / raw)
To: gcc-patches
Cc: Tom Tromey, Jason Merrill, Cary Coutant, Jakub Jelinek,
David Edelsohn, Segher Boessenkool, Kewen Lin
On Apr 14, 2023, Alexandre Oliva <oliva@adacore.com> wrote:
> On Mar 23, 2023, Alexandre Oliva <oliva@adacore.com> wrote:
>> This patch introduces infrastructure for targets to add an offset to
>> the label issued after the call_insn to set the call_return_pc
>> attribute. This will be used on rs6000, that sometimes issues another
>> instruction after the call proper as part of a call insn.
> Ping?
> https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614452.html
> https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614453.html
Ping?
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
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