[Bug rtl-optimization/105231] [12 Regression] ICE: in rtl_verify_bb_insns, at cfgrtl.cc:2797 (flow control insn inside a basic block) with custom flags since r12-4767-g81342e95827f77c0

[ebotcazou at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105231

--- Comment #21 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> I'm not sure that's a general enough fix though since we seem to drop
> the REG_EQUAL note and as soon as we do that there's a disconnect
> between what CFG generation thinks throws and what combine thinks
> is good enough to put a REG_EH_REGION note on.

Yes, we actually drop 2 REG_EQUAL notes:

(insn 22 17 78 3 (set (reg:SF 92)
        (mem/u/c:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2]) [0  S4 A32]))
"pr105231.c":6:3 142 {*movsf_internal}
     (expr_list:REG_EQUAL (const_double:SF 1.8446744073709551616e+19
[0x0.8p+65])
        (nil)))

(insn 78 22 24 3 (set (reg:XF 99)
        (float_extend:XF (reg:SF 92))) 166 {*extendsfxf2_i387}
     (expr_list:REG_DEAD (reg:SF 92)
        (expr_list:REG_EQUAL (const_double:XF 1.8446744073709551616e+19
[0x0.8p+65])
            (nil))))

-->

(insn 78 22 24 3 (set (reg:XF 99)
        (float_extend:XF (mem/u/c:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2]) [0
 S4 A32]))) 166 {*extendsfxf2_i387}
     (expr_list:REG_EH_REGION (const_int 1 [0x1])
        (nil)))

so an immediate solution would be to preserve the one on insn 78 (and arrange
for the purge_dead_edge magic to trigger again).