https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120941
--- Comment #24 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Filip Kastl from comment #23)
> ---- testcase.c ----
> enum { ST, SB, ET, EB, WT, WB }
> LBM_initializeGrid() {
> double *grid;
> grid[ST] = grid[SB] = grid[ET] = grid[EB] =
> grid[WT] = grid[WB] = 1.0 / 36.0;
> }
> ---- ----
>
> Compile with -Ofast -march=znver2 -c -fdump-rtl-all. In the dump, you
> should find:
>
> ----------------
> Replace:
>
> (insn 5 2 7 2 (set (reg:V2DF 101)
> (vec_duplicate:V2DF (mem/u/c:DF (symbol_ref/u:DI ("*.LC1") [flags
> 0x2]) [0 S8 A64]))) "testcase.c":5:16 7168 {vec_dupv2df}
> (expr_list:REG_EQUAL (const_vector:V2DF [
> (const_double:DF
> 2.7777777777777776235801354687282582744956016540527344e-2
> [0x0.e38e38e38e38ep-5]) repeated x2
> ])
> (nil)))
>
> with:
>
> (insn 5 2 7 2 (set (reg:V2DF 101)
> (subreg:V2DF (reg:V4DF 104) 0)) "testcase.c":5:16 2429
> {movv2df_internal}
> (expr_list:REG_EQUAL (const_vector:V2DF [
> (const_double:DF
> 2.7777777777777776235801354687282582744956016540527344e-2
> [0x0.e38e38e38e38ep-5]) repeated x2
> ])
> (nil)))
>
> deferring rescan insn with uid = 5.
>
> Replace:
>
> (insn 8 7 10 2 (set (reg:V4DF 103)
> (vec_duplicate:V4DF (mem/u/c:DF (symbol_ref/u:DI ("*.LC1") [flags
> 0x2]) [0 S8 A64]))) "testcase.c":4:12 9260 {vec_dupv4df}
> (expr_list:REG_EQUAL (const_vector:V4DF [
> (const_double:DF
> 2.7777777777777776235801354687282582744956016540527344e-2
> [0x0.e38e38e38e38ep-5]) repeated x4
> ])
> (nil)))
>
> with:
>
> (insn 8 7 10 2 (set (reg:V4DF 103)
> (reg:V4DF 104)) "testcase.c":4:12 2428 {movv4df_internal}
> (expr_list:REG_EQUAL (const_vector:V4DF [
> (const_double:DF
> 2.7777777777777776235801354687282582744956016540527344e-2
> [0x0.e38e38e38e38ep-5]) repeated x4
> ])
> (nil)))
> ------------------
>
> Works even on the current master (r16-2091-g20407a41e84044). I got this
> from machine reducing the source files using cvise.
Why is it bad for znver2?
