Re: [PATCH] RISC-V: VECT: Remember to assert any_known_not_updated_vssa

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Nov 6, 2023 at 2:02 PM Maxim Blinov <maxim.a.blinov@gmail.com> wrote:
>
> From: Maxim Blinov <maxim.blinov@imgtec.com>
>
> This patch is based on and intended for the vendors/riscv/gcc-13-with-riscv-opts branch - please apply if looks OK.
>
> Fixes the following ICEs that I'm seeing:
>
> FAIL: gcc.dg/vect/O3-pr49087.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/no-scevccp-pr86725-1.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/no-scevccp-pr86725-2.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/no-scevccp-pr86725-3.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/no-scevccp-pr86725-4.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/pr94443.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/pr94443.c -flto -ffat-lto-objects (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/slp-50.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/slp-50.c -flto -ffat-lto-objects (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/vect-cond-13.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/vect-cond-13.c -flto -ffat-lto-objects (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/vect-live-6.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.dg/vect/vect-live-6.c -flto -ffat-lto-objects (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.target/riscv/rvv/autovec/partial/live-1.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
> FAIL: gcc.target/riscv/rvv/autovec/partial/live-2.c (internal compiler error: in vect_transform_loops, at tree-vectorizer.cc:1032)
>
> -- >8 --
>
> When we create a VEC_EXPAND gimple stmt:
>
>           /* SCALAR_RES = VEC_EXTRACT <VEC_LHS, LEN + BIAS - 1>.  */
>           tree scalar_res
>             = gimple_build (&stmts, CFN_VEC_EXTRACT, TREE_TYPE (vectype),
>                             vec_lhs_phi, last_index);
>
> Under the hood we are really just creating a GIMPLE_CALL stmt. Later
> on, when we `gsi_insert_seq_before` our stmts:
>
>       if (stmts)
>         {
>           gimple_stmt_iterator exit_gsi = gsi_after_labels (exit_bb);
>           gsi_insert_seq_before (&exit_gsi, stmts, GSI_SAME_STMT);
>
> We eventually run into tree-ssa-operands.cc:1147:
>
>   operands_scanner (fn, stmt).build_ssa_operands ();
>
> Since VEC_EXPAND is *not* marked with ECF_NOVOPS, ECF_CONST, or
> ECF_PURE flags in internal-fn.def, when

I see

DEF_INTERNAL_OPTAB_FN (VEC_EXTRACT, ECF_CONST | ECF_NOTHROW,
                       vec_extract, vec_extract)

?

> `operand_scanner::parse_ssa_operands` comes across our
> VEC_EXTRACT-type GIMPLE_CALL, it generates a `gimple_vop()` artificial
> variable.
>
> `operand_scanner::finalize_ssa_defs` then picks this up, so our final
> stmt goes from
>
> _73 = .VEC_EXTRACT (vect_last_9.56_71, _72);
>
> to
>
> # .MEM = VDEF <>
> _73 = .VEC_EXTRACT (vect_last_9.56_71, _72);
>
> But more importantly it marks us as `ssa_renaming_needed`, in
> tree-ssa-operands.cc:420:
>
>   /* If we have a non-SSA_NAME VDEF, mark it for renaming.  */
>   if (gimple_vdef (stmt)
>       && TREE_CODE (gimple_vdef (stmt)) != SSA_NAME)
>     {
>       fn->gimple_df->rename_vops = 1;
>       fn->gimple_df->ssa_renaming_needed = 1;
>     }
>
> This then proceeds to crash the compiler when we are about to leave
> `vect_transform_loops`:
>
>   if (need_ssa_update_p (cfun))
>     {
>       gcc_assert (loop_vinfo->any_known_not_updated_vssa);
>       fun->gimple_df->ssa_renaming_needed = false;
>       todo |= TODO_update_ssa_only_virtuals;
>     }
>
> Since,
>
> - `need_ssa_update_p (cfun)` is true (it was set when we generated a
>   memory vdef)
> - `loop_vinfo->any_known_not_updated_vssa` is false
>
> As the code currently stands, creating a gimple stmt containing a
> VEC_EXTRACT should always generate a memory vdef, therefore we should
> remember to mark `loop_vinfo->any_known_not_updated_vssa` afterwards.
>
> gcc/ChangeLog:
>
>         * tree-vect-loop.cc (vectorizable_live_operation): Remember to
>         assert loop_vinfo->any_known_not_updated_vssa if we are inserting
>         a call to VEC_EXPAND.
> ---
>  gcc/tree-vect-loop.cc | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index c8df2c88575..53c3a31d2a8 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -10155,6 +10155,11 @@ vectorizable_live_operation (vec_info *vinfo,
>             = gimple_build (&stmts, CFN_VEC_EXTRACT, TREE_TYPE (vectype),
>                             vec_lhs_phi, last_index);
>
> +         /* We've expanded SSA at this point, and since VEC_EXTRACT
> +            will generate vops, make sure to tell GCC that we need to
> +            update SSA.  */
> +         loop_vinfo->any_known_not_updated_vssa = true;
> +
>           /* Convert the extracted vector element to the scalar type.  */
>           new_tree = gimple_convert (&stmts, lhs_type, scalar_res);
>         }
> --
> 2.34.1
>