For the record, I can't approve this, but...
"H.J. Lu" <hjl.to...@gmail.com> writes:
> i386,md has
>
> (define_expand "extzv"
> [(set (match_operand:SI 0 "register_operand")
> (zero_extract:SI (match_operand 1 "ext_register_operand")
> (match_operand:SI 2 "const8_operand")
> (match_operand:SI 3 "const8_operand")))]
> ""
>
> and mode_for_extraction picks word_mode for operand 1 since
> its mode is VOIDmode. This patch changes mode_for_extraction
> to return the mode of operand 1 if the pattern accepts any mode.
> I added *jcc_btsi_mask_2 since combine now tries a different
> pattern, which leads to test failures on gcc.target/i386/bt-mask-1.c
> and gcc.target/i386/bt-mask-2. I didn't update *jcc_btsi_mask_1
> instead since I am not sure if it is used elsewhere. Tested on
> Linux/x86-64 and Linux/x32. OK for trunk?
the mode of the extraction operand is defined to be word_mode
for registers (see md.texi), so that at least would need to
be updated. But I'm not convinced that the wanted_inner_mode here:
if (! in_dest && unsignedp
- && mode_for_extraction (EP_extzv, -1) != MAX_MACHINE_MODE)
+ && mode_for_extraction (EP_extzv, -1, VOIDmode) != MAX_MACHINE_MODE)
{
- wanted_inner_reg_mode = mode_for_extraction (EP_extzv, 1);
- pos_mode = mode_for_extraction (EP_extzv, 3);
- extraction_mode = mode_for_extraction (EP_extzv, 0);
+ wanted_inner_reg_mode = mode_for_extraction (EP_extzv, 1,
+ inner_mode);
+ pos_mode = mode_for_extraction (EP_extzv, 3, VOIDmode);
+ extraction_mode = mode_for_extraction (EP_extzv, 0, VOIDmode);
}
is right. inner_mode is the mode of the thing we're extracting,
which doesn't ncessarily have anything to do with what the ext*
patterns support.
FWIW, in reply to your force_to_mode message, gen_lowpart_for_combine
looks a bit odd:
if (omode == imode)
return x;
/* Return identity if this is a CONST or symbolic reference. */
if (omode == Pmode
&& (GET_CODE (x) == CONST
|| GET_CODE (x) == SYMBOL_REF
|| GET_CODE (x) == LABEL_REF))
return x;
So if we know the modes are different, we nevertheless return the
original mode for CONST, SYMBOL_REF or LABEL_REF. Surely the caller
isn't going to be expecting that? If we're not prepared to change
the mode to the one that the caller asked for then I think we should
goto fail instead.
I don't know if you're hitting that or not.
Richard
