https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112599
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Robin Dapp <rd...@gcc.gnu.org>: https://gcc.gnu.org/g:35a688f434159a923420310860c5bc721e29a741 commit r14-5777-g35a688f434159a923420310860c5bc721e29a741 Author: Juzhe-Zhong <juzhe.zh...@rivai.ai> Date: Thu Nov 23 19:59:52 2023 +0800 RISC-V: Disable AVL propagation of vrgather instruction This patch fixes following FAILs in zvl1024b of both RV32/RV64: FAIL: gcc.c-torture/execute/990128-1.c -O2 execution test FAIL: gcc.c-torture/execute/990128-1.c -O2 -flto -fno-use-linker-plugin -flto-partition=none execution test FAIL: gcc.c-torture/execute/990128-1.c -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects execution test FAIL: gcc.c-torture/execute/990128-1.c -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test FAIL: gcc.c-torture/execute/990128-1.c -O3 -g execution test FAIL: gcc.dg/torture/pr58955-2.c -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test The root case can be simpliy described in this following small case: https://godbolt.org/z/7GaxbEGzG typedef int64_t v1024b __attribute__ ((vector_size (128))); void foo (void *out, void *in, int64_t a, int64_t b) { v1024b v = {a,a,a,a,a,a,a,a,a,a,a,a,a,a,a,a}; v1024b v2 = {b,b,b,b,b,b,b,b,b,b,b,b,b,b,b,b}; v1024b index = *(v1024b*)in; v1024b v3 = __builtin_shuffle (v, v2, index); __riscv_vse64_v_i64m1 (out, (vint64m1_t)v3, 10); } Incorrect ASM: foo: li a5,31 vsetivli zero,10,e64,m1,ta,mu vmv.v.x v2,a5 vl1re64.v v1,0(a1) vmv.v.x v4,a2 vand.vv v1,v1,v2 vmv.v.x v3,a3 vmsgeu.vi v0,v1,16 vrgather.vv v2,v4,v1 --> AVL = VLMAX according to codes. vadd.vi v1,v1,-16 vrgather.vv v2,v3,v1,v0.t --> AVL = VLMAX according to codes. vse64.v v2,0(a0) --> AVL = 10 according to codes. ret For vrgather dest, source, index instruction, when index may has the value > the following store AVL that is index value > 10. In this situation, the codes above will end up with: The source vector of vrgather has undefined value on index >= AVL (which is 10 in this case). So disable AVL propagation for vrgather instruction. PR target/112599 PR target/112670 gcc/ChangeLog: * config/riscv/riscv-avlprop.cc (alv_can_be_propagated_p): New function. (vlmax_ta_p): Disable vrgather AVL propagation. gcc/testsuite/ChangeLog: * gcc.target/riscv/rvv/autovec/pr112599-1.c: New test.
