On 6/7/2026 10:11 PM, Monk Chiang wrote:
The trampoline code generation for Zicfilp (CFI landing pads) uses
three registers and includes a redundant LUI instruction.
Before this patch, the trampoline code was:
lpad 0
auipc t3, 0
l[wd] t0, (target_function_offset - 4)(t3)
l[wd] t3, (static_chain_offset - 4)(t3)
lui t2, 0
jr t0
This uses three registers (t0, t2, t3) and has a redundant "lui t2, 0"
instruction that is never used.
After this patch, the trampoline code is:
lpad 0
auipc t3, 0
l[wd] t2, (target_function_offset - 4)(t3)
l[wd] t3, (static_chain_offset - 4)(t3)
jr t2
nop
The optimization removes the redundant LUI instruction, uses only two
registers (t2, t3), and adds a nop for proper 8-byte alignment to avoid
-Wpadded warnings.
Changes in v2:
- Fix zicfilp-trampoline test for Linux targets.
- Fix line length exceeding 80 characters.
gcc/
* config/riscv/riscv.cc (riscv_trampoline_init): Remove redundant
LUI instruction.
gcc/testsuite/
* gcc.target/riscv/zicfilp-trampoline.c: New test.
THanks. I know you've got commit privs, but we've got the patchwork
meeting in a couple hours and there's no sense in having this on the
list of patches to review, so I went ahead and pushed it myself.
Thanks again!
jeff
