[Bug rtl-optimization/43147] SSE shuffle merge

hjl.tools at gmail dot com gcc-bugzilla@gcc.gnu.org
Tue Aug 24 01:57:42 GMT 2021


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43147

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|hjl.tools at gmail dot com         |unassigned at gcc dot gnu.org
          Component|target                      |rtl-optimization
            Version|4.4.1                       |12.0

--- Comment #14 from H.J. Lu <hjl.tools at gmail dot com> ---
From

https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577991.html

Trying 5 -> 7:
    5: r85:V4SF=[`*.LC0']
      REG_EQUAL const_vector
    7: r84:V4SF=vec_select(vec_concat(r85:V4SF,r85:V4SF),parallel)
      REG_DEAD r85:V4SF
      REG_EQUAL const_vector
Failed to match this instruction:
(set (reg:V4SF 84)
    (const_vector:V4SF [
            (const_double:SF 3.0e+0 [0x0.cp+2])
            (const_double:SF 2.0e+0 [0x0.8p+2])
            (const_double:SF 4.0e+0 [0x0.8p+3])
            (const_double:SF 1.0e+0 [0x0.8p+1])
        ]))

(insn 5 2 7 2 (set (reg:V4SF 85)
        (mem/u/c:V4SF (symbol_ref/u:DI ("*.LC0") [flags 0x2]) [0  S16
A128]))
"/export/users/liuhongt/install/git_trunk_master_native/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include/xmmintrin.h":746:19
1600 {movv4sf_internal}
     (expr_list:REG_EQUAL (const_vector:V4SF [
                (const_double:SF 4.0e+0 [0x0.8p+3])
                (const_double:SF 3.0e+0 [0x0.cp+2])
                (const_double:SF 2.0e+0 [0x0.8p+2])
                (const_double:SF 1.0e+0 [0x0.8p+1])
            ])
        (nil)))
(insn 7 5 11 2 (set (reg:V4SF 84)
        (vec_select:V4SF (vec_concat:V8SF (reg:V4SF 85)
                (reg:V4SF 85))
            (parallel [
                    (const_int 1 [0x1])
                    (const_int 2 [0x2])
                    (const_int 4 [0x4])
                    (const_int 7 [0x7])
                ])))
"/export/users/liuhongt/install/git_trunk_master_native/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include/xmmintrin.h":746:19
3015 {sse_shufps_v4sf}
     (expr_list:REG_DEAD (reg:V4SF 85)
        (expr_list:REG_EQUAL (const_vector:V4SF [
                    (const_double:SF 3.0e+0 [0x0.cp+2])
                    (const_double:SF 2.0e+0 [0x0.8p+2])
                    (const_double:SF 4.0e+0 [0x0.8p+3])
                    (const_double:SF 1.0e+0 [0x0.8p+1])
                ])
            (nil))))

I think pass_combine should be extended to force illegitimate constant
to constant pool and recog load insn again, It looks like a general
optimization that better not do it in the backend.


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