On Tue, Nov 12, 2024 at 1:49 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > When passing 0xff as an unsigned char function argument, the C frontend > promotion will promote it to int: > > <integer_cst 0x7fffe6aa23a8 type <integer_type 0x7fffe98225e8 int> constant > 255> > > and expand_normal always returns the rtx value using the sign-extended > representation, > > (const_int 255 [0xff]) > > If the C frontend doesn't promote unsigned char to int, expand_normal will > get > > <integer_cst 0x7fffe9824018 type <integer_type 0x7fffe9822348 unsigned char > > co > nstant 255> > > and return > > (const_int -1 [0xffffffffffffffff])
that looks wrong to me, but in other places we ensure to use trunc_int_for_mode (), not some odd function like you introduce here? Richard. > > gnu-tgl-3:pts/6[168]> head -50 > /tmp/0001-i386-Add-ix86_expand_integer_cst_argument.patch > From d9dddaad6254cca11b0a55c18291180d6d8d7524 Mon Sep 17 00:00:00 2001 > From: "H.J. Lu" <hjl.to...@gmail.com> > Date: Tue, 12 Nov 2024 09:03:31 +0800 > Subject: [PATCH] i386: Add ix86_expand_integer_cst_argument > > When passing 0xff as an unsigned char function argument, the C frontend > promotion will promote it to int: > > <integer_cst 0x7fffe6aa23a8 type <integer_type 0x7fffe98225e8 int> constant > 255> > > and expand_normal always returns the rtx value using the sign-extended > representation, > > (const_int 255 [0xff]) > > If the C frontend doesn't promote unsigned char to int, expand_normal will > get > > <integer_cst 0x7fffe9824018 type <integer_type 0x7fffe9822348 unsigned char > > co > nstant 255> > > and return > > (const_int -1 [0xffffffffffffffff]) > > Add ix86_expand_integer_cst_argument to expand the argument before calling > fixup_modeless_constant to extract the 8-bit/16-bit integer constants to > always return > > (const_int 255 [0xff]) > > in this case. > > PR middle-end/14907 > * config/i386/i386-expand.cc (ix86_expand_integer_cst_argument): > New function. > (ix86_expand_args_builtin): Call ix86_expand_integer_cst_argument > to expand the argument before calling fixup_modeless_constant. > (ix86_expand_round_builtin): Likewise. > (ix86_expand_special_args_builtin): Likewise. > (ix86_expand_builtin): Likewise. > > -- > H.J.
