https://gcc.gnu.org/g:f5166f5badb190eec5d3707fe25ad33febf1969e
commit r16-6650-gf5166f5badb190eec5d3707fe25ad33febf1969e Author: Alexandre Oliva <[email protected]> Date: Thu Jul 10 22:21:31 2025 -0300 arm: prevent impossible tail- long-calls with static chain [PR119430] When a function call uses up all argument registers, and needs IP for the static chain, there aren't any call-clobbered registers 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. gcc/ChangeLog PR target/119430 * config/arm/arm.cc (arm_function_ok_for_sibcall): Disable sibcalls for long-calls that use all call-clobbered general-purpose registers, including the static chain. Diff: --- gcc/config/arm/arm.cc | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc index ec21fb96b668..0a1f6612d07f 100644 --- a/gcc/config/arm/arm.cc +++ b/gcc/config/arm/arm.cc @@ -7983,10 +7983,14 @@ arm_function_ok_for_sibcall (tree decl, tree exp) address. But we only have r0-r3 and ip in that class. If r0-r3 all hold 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())) + to disable the tail call if nothing is available. Long-calls are + effectively handled as indirect calls, so handle that as well. */ + 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;
