When a function call uses up all argument registers, and needs IP for
the static chain, there isn't any call-clobbered register left for
reload to assign as the sibcall target, when -mlong-calls is enabled.
Use the same logic that does the job for indirect calls to prevent
tail calls in this case.
With this change, it is possible to bootstrap armv7a-linux-gnu with
both -O3 and lto, but only with both -mlong-calls and
-ffunction-sections.
Without -mlong-calls, linker veneer thunks may clobber the static
chain register set up by callers in one lto unit, preventing them from
reaching the callee in a separate lto unit. -ffunction-sections is
required for -mlong-calls to be effective, because both caller and
callee are in the same section, and that disables long-calls when
!flag_reorder_blocks_and_partition.
Regstrapped on armv7a-linux-gnu with the caveats above. Ok to install?
for gcc/ChangeLog
PR target/119430
* gcc/config/arm.cc (arm_function_ok_for_sibcall): Disable
sibcalls for long-calls that use all call-clobbered
general-purpose registers, including the static chain.
---
gcc/config/arm/arm.cc | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index bde06f3fa8664..8956b8a645f2c 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -7946,9 +7946,12 @@ arm_function_ok_for_sibcall (tree decl, tree exp)
function arguments, then we can only use IP. But IP may be needed in the
epilogue (for PAC validation), or for passing the static chain. We have
to disable the tail call if nothing is available. */
- if (!decl
- && ((CALL_EXPR_BY_DESCRIPTOR (exp) && !flag_trampolines)
- || arm_current_function_pac_enabled_p()))
+ if ((!decl
+ && ((CALL_EXPR_BY_DESCRIPTOR (exp) && !flag_trampolines)
+ || arm_current_function_pac_enabled_p ()))
+ || (decl && arm_is_long_call_p (decl)
+ && (CALL_EXPR_STATIC_CHAIN (exp)
+ || arm_current_function_pac_enabled_p ())))
{
tree fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
CUMULATIVE_ARGS cum;
--
Alexandre Oliva, happy hacker https://blog.lx.oliva.nom.br/
Free Software Activist FSFLA co-founder GNU Toolchain Engineer
Learn the truth about Richard Stallman at https://stallmansupport.org/
