https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91386
Wilco <wilco at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |wilco at gcc dot gnu.org
--- Comment #12 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #10)
> I'm attaching all tree and rtl dumps for the problematic LTRANS unit:
> https://drive.google.com/file/d/1CW4cWvpm1VVXFIP80XCf1IzYXWwTsynZ/
> view?usp=sharing
>
> I can confirm what Andreas sees:
>
> (note 8303 8031 7890 4 NOTE_INSN_PROLOGUE_END)
> (insn:TI 7890 8303 7889 4 (set (mem/c:DI (plus:DI (reg/f:DI 31 sp)
> (const_int 704 [0x2c0])) [63 %sfp+-2912 S8 A64])
> (reg/f:DI 2 x2 [1833])) "../include/list.h":29:13 47 {*movdi_aarch64}
> (nil))
> (insn 7889 7890 7887 4 (set (mem/c:DI (plus:DI (reg/f:DI 31 sp)
> (const_int 712 [0x2c8])) [63 %sfp+-2904 S8 A64])
> (reg/f:DI 3 x3 [1834])) "../include/list.h":29:13 47 {*movdi_aarch64}
> (nil))
>
> gets transformed by peephole2 to:
> (note 8303 8031 8556 4 NOTE_INSN_PROLOGUE_END)
> (insn 8556 8303 7887 4 (parallel [
> (set (mem/c:DI (plus:DI (reg:DI 7 x7)
> (const_int 8 [0x8])) [63 %sfp+-2912 S8 A64])
> (reg/f:DI 2 x2 [1833]))
> (set (mem/c:DI (plus:DI (reg:DI 7 x7)
> (const_int 16 [0x10])) [63 %sfp+-2904 S8 A64])
> (reg/f:DI 3 x3 [1834]))
> ]) "../include/list.h":29:13 -1
> (nil))
>
> I don't know what's the meaning of x7 register, but it's not set during main
> function execution.
Basically the backend can combine up to 4 loads or stores and insert an
addressing instruction so that all offsets are in range
(aarch64_gen_adjusted_ldpstp). It appears a later optimization removes the
initialization of x7 as dead and so the address is wrong.
The key question is how does one dump rtl with -flto? It doesn't work at all,
making debugging this difficult...
