On Thu, Jan 18, 2024 at 01:57:49PM +0100, Richard Biener wrote:
> > - RTL expansion expectes TARGET_MEM_REF to always address actual
> > memory. */
> > + RTL expansion expectes TARGET_MEM_REF to always address actual memory.
> > + Also, force to stack non-BLKmode vars accessed through
> > VIEW_CONVERT_EXPR
> > + to BLKmode BITINT_TYPEs. */
> > else if (TREE_CODE (t) == TARGET_MEM_REF
> > || (TREE_CODE (t) == MEM_REF
> > && TYPE_SIZE (TREE_TYPE (t))
> > - && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t)))))
> > + && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t))))
> > + || (TREE_CODE (t) == VIEW_CONVERT_EXPR
> > + && TREE_CODE (TREE_TYPE (t)) == BITINT_TYPE
> > + && TYPE_MODE (TREE_TYPE (t)) == BLKmode))
>
> I'm still not getting what's special about BITINT_TYPE here so
> shouldn't that apply to all BLKmode V_C_E? But sure we can for
> now just handle BITINT_TYPE.
>
> That hunk looks OK to me.
The == BITINT_TYPE check is non-essential, was just trying to keep existing
behavior otherwise. I can certainly drop that.
> > --- gcc/expr.cc.jj 2024-01-12 10:07:58.194851657 +0100
> > +++ gcc/expr.cc 2024-01-18 13:38:19.677556646 +0100
> > @@ -12382,6 +12382,17 @@ expand_expr_real_1 (tree exp, rtx target
> > }
> > }
> >
> > + /* Ensure non-BLKmode array VAR_DECLs VCEd to BLKmode BITINT_TYPE
> > + aren't promoted to registers. */
> > + if (op0 == NULL_RTX
> > + && mode == BLKmode
> > + && TREE_CODE (type) == BITINT_TYPE
> > + && VAR_P (treeop0)
> > + && DECL_MODE (treeop0) != BLKmode
> > + && DECL_RTL_SET_P (treeop0)
> > + && MEM_P (DECL_RTL (treeop0)))
> > + op0 = adjust_address (DECL_RTL (treeop0), BLKmode, 0);
> > +
> > if (!op0)
> > op0 = expand_expr_real (treeop0, NULL_RTX, VOIDmode, modifier,
> > NULL, inner_reference_p);
>
> So we're now sure we have MEM_P (op0) after expand_expr_real,
> even without this change, right? What's wrong with the
> suggestion to use
I wasn't sure if VAR_P (treeop0) && MEM_P (DECL_RTL (treeop0)) implies that
expand_expr_real will return a MEM, but I'm not able to find a path in which
it would return something different, so maybe ok.
> if (mode == GET_MODE (op0) || (mode == BLKmode && MEM_P (op0))
>
> thus not run into any of the special-casing? We're doing just
It is true the later code will then do:
>
> op0 = adjust_address (op0, mode, 0);
so perhaps it is ok as you wrote it (though perhaps adding it as a separate
else if would allow a separate comment).
Jakub
