Resent to cc Juzhe. ------
Hi all, A simple assembly check has been added in this version. Previous version: https://gcc.gnu.org/pipermail/gcc-patches/2024-September/662783.html Thanks, Bohan ------ The current vsetvl pass eliminates a vsetvl instruction when the previous info is "available," but does not when "compatible." This can lead to not only redundancy, but also incorrect behaviors when the previous info happens to be compatible with a later vector instruction, which ends of using the vsetvl info that should have been eliminated, as is shown in the testcase. This patch eliminates the vsetvl when the previous info is "compatible." gcc/ChangeLog: * config/riscv/riscv-vsetvl.cc (pre_vsetvl::fuse_local_vsetvl_info): Delete vsetvl insn when `prev_info` is compatible gcc/testsuite/ChangeLog: * gcc.target/riscv/rvv/vsetvl/vsetvl_bug-4.c: New test. --- gcc/config/riscv/riscv-vsetvl.cc | 3 +++ .../riscv/rvv/vsetvl/vsetvl_bug-4.c | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+) create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl_bug-4.c diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc index ce831685439..030ffbe2ebb 100644 --- a/gcc/config/riscv/riscv-vsetvl.cc +++ b/gcc/config/riscv/riscv-vsetvl.cc @@ -2796,6 +2796,9 @@ pre_vsetvl::fuse_local_vsetvl_info () curr_info.dump (dump_file, " "); } m_dem.merge (prev_info, curr_info); + if (!curr_info.vl_used_by_non_rvv_insn_p () + && vsetvl_insn_p (curr_info.get_insn ()->rtl ())) + m_delete_list.safe_push (curr_info); if (curr_info.get_read_vl_insn ()) prev_info.set_read_vl_insn (curr_info.get_read_vl_insn ()); if (dump_file && (dump_flags & TDF_DETAILS)) diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl_bug-4.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl_bug-4.c new file mode 100644 index 00000000000..04a8ff2945a --- /dev/null +++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/vsetvl_bug-4.c @@ -0,0 +1,19 @@ +/* { dg-do compile } */ +/* { dg-options "-march=rv64gcv -mabi=lp64d -O2 -fno-schedule-insns -fdump-rtl-vsetvl-details" } */ + +#include <riscv_vector.h> + +vuint16m1_t +foo (vuint16m1_t a, vuint16m1_t b, size_t avl) +{ + size_t vl; + vuint16m1_t ret; + uint16_t c = __riscv_vmv_x_s_u16m1_u16(a); + vl = __riscv_vsetvl_e8mf2 (avl); + ret = __riscv_vadd_vx_u16m1 (a, c, avl); + ret = __riscv_vadd_vv_u16m1 (ret, a, vl); + return ret; +} + +/* { dg-final { scan-rtl-dump "Eliminate insn" "vsetvl" } } */ +/* { dg-final { scan-assembler-times {vsetvli} 2 } } */ -- 2.17.1
