https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112399
--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Pan Li <pa...@gcc.gnu.org>: https://gcc.gnu.org/g:f1e084c6c3ef1d1233e35823dacfdf9cee722430 commit r14-5179-gf1e084c6c3ef1d1233e35823dacfdf9cee722430 Author: Juzhe-Zhong <juzhe.zh...@rivai.ai> Date: Mon Nov 6 11:34:26 2023 +0800 RISC-V: Enhance AVL propagation for complicate reduction auto-vectorization I notice we failed to AVL propagate for reduction with more complicate situation: double foo (double *__restrict a, double *__restrict b, double *__restrict c, int n) { double result = 0; for (int i = 0; i < n; i++) result += a[i] * b[i] * c[i]; return result; } vsetvli a5,a3,e8,mf8,ta,ma -> should be fused into e64m1,TU slli a4,a5,3 vle64.v v3,0(a0) vle64.v v1,0(a1) vsetvli a6,zero,e64,m1,ta,ma -> redundant vfmul.vv v1,v1,v3 vsetvli zero,a5,e64,m1,tu,ma -> redundant vle64.v v3,0(a2) vfmacc.vv v2,v1,v3 add a0,a0,a4 add a1,a1,a4 add a2,a2,a4 sub a3,a3,a5 bne a3,zero,.L3 The failed AVL propgation causes redundant AVL/VL togglling. The root cause as follows: vsetvl a5, zero vadd.vv def r136 vsetvl zero, a3, ... TU vsub.vv (use r136) We propagate AVL (r136) from 'vsub.vv' into 'vadd.vv' when 'vsub.vv' is TA policy. However, it's too restrict so we missed optimization here. We enhance AVL propation for TU policy for following situation: vsetvl a5, zero vadd.vv def r136 vsetvl zero, a3, ... TU vsub.vv (use r136, merge != r136) Note that we should only propagate AVL when merge != r136 for 'vsub.vv' doesn't depend on the tail elements. After this patch: vsetvli a5,a3,e64,m1,tu,ma slli a4,a5,3 vle64.v v3,0(a0) vle64.v v1,0(a1) vfmul.vv v1,v1,v3 vle64.v v3,0(a2) vfmacc.vv v2,v3,v1 add a0,a0,a4 add a1,a1,a4 add a2,a2,a4 sub a3,a3,a5 bne a3,zero,.L3 PR target/112399 gcc/ChangeLog: * config/riscv/riscv-avlprop.cc (pass_avlprop::get_vlmax_ta_preferred_avl): Enhance AVL propagation. * config/riscv/t-riscv: Add new include. gcc/testsuite/ChangeLog: * gcc.target/riscv/rvv/vsetvl/imm_switch-2.c: Adapt test. * gcc.target/riscv/rvv/autovec/pr112399.c: New test.
