On Thu, 27 Jan 2022, Richard Biener wrote: > > Index: gcc/gcc/c/c-typeck.cc > > =================================================================== > > --- gcc.orig/gcc/c/c-typeck.cc > > +++ gcc/gcc/c/c-typeck.cc > > @@ -49,6 +49,7 @@ along with GCC; see the file COPYING3. > > #include "gomp-constants.h" > > #include "spellcheck-tree.h" > > #include "gcc-rich-location.h" > > +#include "optabs-query.h" > > #include "stringpool.h" > > #include "attribs.h" > > #include "asan.h" > > @@ -11923,7 +11924,9 @@ build_binary_op (location_t location, en > > bool maybe_const = true; > > tree sc; > > sc = c_fully_fold (op0, false, &maybe_const); > > - sc = save_expr (sc); > > + if (optab_handler (vec_duplicate_optab, > > + TYPE_MODE (type1)) == CODE_FOR_nothing) > > + sc = save_expr (sc); > > This doesn't make much sense - I suppose the CONSTRUCTOR retains > TREE_SIDE_EFFECTS but such flag has no meaning on GIMPLE > and thus should have been cleared during gimplification or in the end > ignored by RTL expansion.
This is how the expression built here eventually looks in `store_constructor': (gdb) print exp $41 = <constructor 0x7ffff5c06ba0> (gdb) pt <constructor 0x7ffff5c06ba0 type <vector_type 0x7ffff5e7ea48 v4sf type <real_type 0x7ffff5cf1260 float sizes-gimplified SF size <integer_cst 0x7ffff5c00f78 constant 32> unit-size <integer_cst 0x7ffff5c00f90 constant 4> align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type 0x7ffff5cf1260 precision:32 pointer_to_this <pointer_type 0x7ffff5cf1848>> sizes-gimplified V4SF size <integer_cst 0x7ffff5c00d80 constant 128> unit-size <integer_cst 0x7ffff5c00d98 constant 16> align:128 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type 0x7ffff5d19648 nunits:4 context <translation_unit_decl 0x7ffff5ec0bb8 v4sf-dup.c>> side-effects length:4 val <ssa_name 0x7ffff5cb0dc8 type <real_type 0x7ffff5cf1260 float> visited var <parm_decl 0x7ffff5f00080 y> def_stmt GIMPLE_NOP version:2> val <ssa_name 0x7ffff5cb0dc8 type <real_type 0x7ffff5cf1260 float> visited var <parm_decl 0x7ffff5f00080 y> def_stmt GIMPLE_NOP version:2> val <ssa_name 0x7ffff5cb0dc8 type <real_type 0x7ffff5cf1260 float> visited var <parm_decl 0x7ffff5f00080 y> def_stmt GIMPLE_NOP version:2> val <ssa_name 0x7ffff5cb0dc8 type <real_type 0x7ffff5cf1260 float> visited var <parm_decl 0x7ffff5f00080 y> def_stmt GIMPLE_NOP version:2>> (gdb) The `side-effects' flag prevents this conditional from executing: /* Try using vec_duplicate_optab for uniform vectors. */ if (!TREE_SIDE_EFFECTS (exp) && VECTOR_MODE_P (mode) && eltmode == GET_MODE_INNER (mode) && ((icode = optab_handler (vec_duplicate_optab, mode)) != CODE_FOR_nothing) && (elt = uniform_vector_p (exp)) && !VECTOR_TYPE_P (TREE_TYPE (elt))) { class expand_operand ops[2]; create_output_operand (&ops[0], target, mode); create_input_operand (&ops[1], expand_normal (elt), eltmode); expand_insn (icode, 2, ops); if (!rtx_equal_p (target, ops[0].value)) emit_move_insn (target, ops[0].value); break; } I don't know what's supposed to clear the flag (and what the purpose of setting it in the first place would be then). > You do not add a testcase so it's hard to see what goes wrong where exactly. This only happens with an out-of-tree microarchitecture and I was unable to find an in-tree target that ever uses the `vec_duplicateM' standard RTL pattern, so I wasn't able to produce a test case that would trigger with upstream code. Code is essentially like: typedef float v4sf __attribute__ ((vector_size (16))); v4sf odd_even (v4sf x, float y) { return x + f; } I considered the Aarch64 one the most likely candidate as it is the one commit be4c1d4a42c5 has been for, but as I noted in the description it does not appear to use it either. It uses `vec_initMN' instead and does the broadcast by hand in the backend. Maybe I'm missing something. Maciej