On 1/10/2025 15:40, Richard Biener wrote:
On Thu, Jul 31, 2025 at 5:47 PM Yangyu Chen <[email protected]> wrote:
When building with LTO, DECL_VINDEX is not always set for virtual
functions, which allows virtual functions to be incorrectly treated as
non-virtual and then being multi-versioned, and causes errors sometimes.
This patch addresses the issue by ensuring that we also check
DECL_VIRTUAL_P in addition to DECL_VINDEX when handling virtual
functions during multiversioning.
I think checking DECL_VINDEX is flawed - it's only relevant for creating
OBJ_TYPE_REFs IIRC. That is, it's irrelevant to GIMPLE and thus freed
in free-lang-data (which we unfortunately run only with -flto).
So, can you test removing the DECL_VINDEX check and only rely on
DECL_VIRTUAL_P?
It can be hard to check since most real-world source code with
optimizations may not use it.
I think we should keep checking these two since DECL_VIRTUAL_P will only
be set by the frontend. For some future passes that may clone a member
function and insert VINDEX, this behavior can be found during
compilation time instead of a runtime crash.
Thanks,
Yangyu Chen
Thanks,
Richard.
gcc/ChangeLog:
* config/aarch64/aarch64.cc
(aarch64_generate_version_dispatcher_body): Check DECL_VIRTUAL_P for virtual
functions for LTO handling.
* config/i386/i386-features.cc
(ix86_generate_version_dispatcher_body): Ditto.
* config/riscv/riscv.cc (riscv_generate_version_dispatcher_body):
Ditto.
* config/rs6000/rs6000.cc (rs6000_generate_version_dispatcher_body):
Ditto.
Signed-off-by: Yangyu Chen <[email protected]>
---
This should also be backported to GCC stable branches.
---
gcc/config/aarch64/aarch64.cc | 2 +-
gcc/config/i386/i386-features.cc | 2 +-
gcc/config/riscv/riscv.cc | 2 +-
gcc/config/rs6000/rs6000.cc | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index fff8d9da49d..fd77e24ce12 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -20763,7 +20763,7 @@ aarch64_generate_version_dispatcher_body (void *node_p)
not. This happens for methods in derived classes that override
virtual methods in base classes but are not explicitly marked as
virtual. */
- if (DECL_VINDEX (versn->decl))
+ if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl))
sorry ("virtual function multiversioning not supported");
fn_ver_vec.safe_push (versn->decl);
diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
index 31f3ee2ef17..043e86ece8e 100644
--- a/gcc/config/i386/i386-features.cc
+++ b/gcc/config/i386/i386-features.cc
@@ -4421,7 +4421,7 @@ ix86_generate_version_dispatcher_body (void *node_p)
not. This happens for methods in derived classes that override
virtual methods in base classes but are not explicitly marked as
virtual. */
- if (DECL_VINDEX (versn->decl))
+ if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl))
sorry ("virtual function multiversioning not supported");
fn_ver_vec.safe_push (versn->decl);
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index a0657323f65..90f2cbce68e 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -13747,7 +13747,7 @@ riscv_generate_version_dispatcher_body (void *node_p)
not. This happens for methods in derived classes that override
virtual methods in base classes but are not explicitly marked as
virtual. */
- if (DECL_VINDEX (versn->decl))
+ if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl))
sorry ("virtual function multiversioning not supported");
fn_ver_vec.safe_push (versn->decl);
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 12dbde2bc63..0c13d524124 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -25656,7 +25656,7 @@ rs6000_generate_version_dispatcher_body (void *node_p)
not. This happens for methods in derived classes that override
virtual methods in base classes but are not explicitly marked as
virtual. */
- if (DECL_VINDEX (version->decl))
+ if (DECL_VIRTUAL_P (version->decl) || DECL_VINDEX (version->decl))
sorry ("Virtual function multiversioning not supported");
fn_ver_vec.safe_push (version->decl);
--
2.49.0
