On 5/30/24 14:32, David Faust wrote:
This commit makes some structural changes to the CTF/BTF debug info
emission. In particular:
a) CTF is new always fully generated and emitted before any
BTF-related procedures are run. This means that BTF-related
functions can change, even irreversibly, the shared in-memory
representation used by the two formats without issue.
b) BTF generation has fewer entry points, and is cleanly divided
into early_finish and finish.
c) BTF is now always emitted at finish (called from dwarf2out_finish),
for all targets in non-LTO builds, rather than being emitted at
early_finish for targets other than BPF CO-RE. In LTO builds,
BTF is emitted at early_finish as before.
Note that this change alone does not alter the contents of BTF at
all, regardless of whether it would have previously been emitted at
early_finish or finish, because the calculation of the BTF to be
emitted is not moved by this patch, only the write-out.
The changes are transparent to both CTF and BTF emission.
OK.
This will work to keep supporting -flto with BTF (for non-BPF targets)
and of course -flto with CTF.
One question/nit below.
gcc/
* btfout.cc (btf_init_postprocess): Rename to...
(btf_early_finish): ...this.
(btf_output): Rename to...
(btf_finish): ...this.
* ctfc.h: Analogous changes.
* dwarf2ctf.cc (ctf_debug_early_finish): Conditionally call
btf_early_finish, or ctf_finalize as appropriate. Emit BTF
here for LTO builds.
(ctf_debug_finish): Always call btf_finish here if generating
BTF info in non-LTO builds.
(ctf_debug_finalize, ctf_debug_init_postprocess): Delete.
* dwarf2out.cc (dwarf2out_early_finish): Remove call to
ctf_debug_init_postprocess.
---
gcc/btfout.cc | 28 +++++++++++++++++++++
gcc/ctfc.h | 4 +--
gcc/dwarf2ctf.cc | 65 +++++++++++++++---------------------------------
gcc/dwarf2out.cc | 2 --
4 files changed, 50 insertions(+), 49 deletions(-)
diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 07f066a47068..1b6a9ed811f0 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -1491,6 +1491,34 @@ btf_finalize (void)
tu_ctfc = NULL;
}
+/* Initial entry point of BTF generation, called at early_finish () after
+ CTF information has possibly been output. Translate all CTF information
+ to BTF, and do any processing that must be done early, such as creating
+ BTF_KIND_FUNC records. */
+
+void
+btf_early_finish (void)
+{
+ btf_init_postprocess ();
+}
+
+/* Late entry point for BTF generation, called from dwarf2out_finish ().
+ Complete and emit BTF information. */
+
+void
+btf_finish (const char * filename)
+{
+ btf_output (filename);
+
+ /* If compiling for BPF with CO-RE info, we cannot deallocate until after
+ CO-RE information is created, which happens very late in BPF backend.
I am wondering if it is more precise to say that "until after contents
for the .BTF.ext section are finalized" ? We have already called the
btf_output () above, which means _some_ CO-RE information is already
created (like the accessor strings for CO-RE relocs that go in the .BTF
section).
+ Therefore, the deallocation (i.e. btf_finalize ()) is delayed until
+ TARGET_ASM_FILE_END for BPF CO-RE. */
+ if (!btf_with_core_debuginfo_p ())
+ btf_finalize ();
+}
+
+
/* Traversal function for all BTF_KIND_FUNC type records. */
bool
diff --git a/gcc/ctfc.h b/gcc/ctfc.h
index fa188bf2f5a4..e7bd93901cfa 100644
--- a/gcc/ctfc.h
+++ b/gcc/ctfc.h
@@ -384,8 +384,8 @@ extern void ctf_init (void);
extern void ctf_output (const char * filename);
extern void ctf_finalize (void);
-extern void btf_output (const char * filename);
-extern void btf_init_postprocess (void);
+extern void btf_early_finish (void);
+extern void btf_finish (const char * filename);
extern void btf_finalize (void);
extern ctf_container_ref ctf_get_tu_ctfc (void);
diff --git a/gcc/dwarf2ctf.cc b/gcc/dwarf2ctf.cc
index dc59569fe560..8f9e2fada9e3 100644
--- a/gcc/dwarf2ctf.cc
+++ b/gcc/dwarf2ctf.cc
@@ -933,30 +933,6 @@ gen_ctf_type (ctf_container_ref ctfc, dw_die_ref die)
return type_id;
}
-/* Prepare for output and write out the CTF debug information. */
-
-static void
-ctf_debug_finalize (const char *filename, bool btf)
-{
- if (btf)
- {
- btf_output (filename);
- /* btf_finalize when compiling BPF applciations gets deallocated by the
- BPF target in bpf_file_end. */
- if (btf_debuginfo_p () && !btf_with_core_debuginfo_p ())
- btf_finalize ();
- }
-
- else
- {
- /* Emit the collected CTF information. */
- ctf_output (filename);
-
- /* Reset the CTF state. */
- ctf_finalize ();
- }
-}
-
bool
ctf_do_die (dw_die_ref die)
{
@@ -996,27 +972,27 @@ ctf_debug_init (void)
add_name_attribute (ctf_unknown_die, "unknown");
}
-/* Preprocess the CTF debug information after initialization. */
-
-void
-ctf_debug_init_postprocess (bool btf)
-{
- /* Only BTF requires postprocessing right after init. */
- if (btf)
- btf_init_postprocess ();
-}
-
/* Early finish CTF/BTF debug info. */
void
ctf_debug_early_finish (const char * filename)
{
- /* Emit CTF debug info early always. */
- if (ctf_debug_info_level > CTFINFO_LEVEL_NONE
- /* Emit BTF debug info early if CO-RE relocations are not
- required. */
- || (btf_debuginfo_p () && !btf_with_core_debuginfo_p ()))
- ctf_debug_finalize (filename, btf_debuginfo_p ());
+ /* Emit the collected CTF information. */
+ if (ctf_debug_info_level > CTFINFO_LEVEL_NONE)
+ ctf_output (filename);
+
+ /* If emitting BTF, start translation to BTF. */
+ if (btf_debuginfo_p ())
+ {
+ btf_early_finish ();
+
+ /* For LTO builds, also emit BTF now. */
+ if (flag_lto && !in_lto_p)
+ btf_finish (filename);
+ }
+ else
+ /* Otherwise, done with the CTF container. */
+ ctf_finalize ();
}
/* Finish CTF/BTF debug info emission. */
@@ -1024,11 +1000,10 @@ ctf_debug_early_finish (const char * filename)
void
ctf_debug_finish (const char * filename)
{
- /* Emit BTF debug info here when CO-RE relocations need to be generated.
- BTF with CO-RE relocations needs to be generated when CO-RE is in effect
- for the BPF target. */
- if (btf_debuginfo_p () && btf_with_core_debuginfo_p ())
- ctf_debug_finalize (filename, btf_debuginfo_p ());
+ /* Emit BTF late, unless this is an LTO build in which case it was
+ already done early. */
+ if (btf_debuginfo_p () && !flag_lto)
+ btf_finish (filename);
}
#include "gt-dwarf2ctf.h"
diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 5b064ffd78ad..e406df8673ce 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -33202,8 +33202,6 @@ dwarf2out_early_finish (const char *filename)
ctf_debug_do_cu (comp_unit_die ());
for (limbo_die_node *node = limbo_die_list; node; node = node->next)
ctf_debug_do_cu (node->die);
- /* Post process the debug data in the CTF container if necessary. */
- ctf_debug_init_postprocess (btf_debuginfo_p ());
ctf_debug_early_finish (filename);
}
