https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97071
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |powerpc64le
Keywords| |missed-optimization
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Right before combine we see the following, still nicely with REG_EQUAL notes
(insn 7 17 9 2 (set (reg:DF 119)
(mem/u/c:DF (unspec:DI [
(symbol_ref/u:DI ("*.LC0") [flags 0x82])
(reg:DI 2 2)
] UNSPEC_TOCREL) [0 S8 A64])) "t.c":3:20 533
{*movdf_hardfloat64}
(expr_list:REG_EQUAL (const_double:DF -3.0e+0 [-0x0.cp+2])
(nil)))
(insn 9 7 14 2 (set (reg:DF 121)
(mem/u/c:DF (unspec:DI [
(symbol_ref/u:DI ("*.LC2") [flags 0x82])
(reg:DI 2 2)
] UNSPEC_TOCREL) [0 S8 A64])) "t.c":3:20 533
{*movdf_hardfloat64}
(expr_list:REG_EQUAL (const_double:DF 3.0e+0 [0x0.cp+2])
(nil)))
(insn 14 9 15 2 (set (reg/i:DF 33 1)
(fma:DF (reg:DF 124)
(reg:DF 119)
(reg:DF 121))) "t.c":4:1 894 {*fmadf4_fpr}
(expr_list:REG_DEAD (reg:DF 124)
(expr_list:REG_DEAD (reg:DF 121)
(expr_list:REG_DEAD (reg:DF 119)
(nil)))))
eventually the easiest pass to teach this to is fwprop though as it already
works DF DEF -> USE. Alternatively PRE could make the subtract and/or the
negated value anticipated.
