On 6/17/24 3:53 AM, Richard Sandiford wrote:
This patch makes target-independent code use force_subreg instead
of simplify_gen_subreg in some places. The criteria were:
(1) The code is obviously specific to expand (where new pseudos
can be created), or at least would be invalid to call when
!can_create_pseudo_p () and temporaries are needed.
(2) The value is obviously an rvalue rather than an lvalue.
(3) The offset wasn't a simple lowpart or highpart calculation;
a later patch will deal with those.
Doing this should reduce the likelihood of bugs like PR115464
occuring in other situations.
gcc/
* expmed.cc (store_bit_field_using_insv): Use force_subreg
instead of simplify_gen_subreg.
(store_bit_field_1): Likewise.
(extract_bit_field_as_subreg): Likewise.
(extract_integral_bit_field): Likewise.
(emit_store_flag_1): Likewise.
* expr.cc (convert_move): Likewise.
(convert_modes): Likewise.
(emit_group_load_1): Likewise.
(emit_group_store): Likewise.
(expand_assignment): Likewise.
[ ... ]
So this has triggered a failure on ft32-elf with this testcase
(simplified from the testsuite):
typedef _Bool bool;
const bool false = 0;
const bool true = 1;
struct RenderBox
{
bool m_positioned : 1;
};
typedef struct RenderBox RenderBox;
void RenderBox_setStyle(RenderBox *thisin)
{
RenderBox *this = thisin;
bool ltrue = true;
this->m_positioned = ltrue;
}
Before this change we generated this:
(insn 13 12 14 (set (reg:QI 47)
(mem/c:QI (plus:SI (reg/f:SI 37 virtual-stack-vars)
(const_int -5 [0xfffffffffffffffb])) [1 ltrue+0 S1 A8]))
"j.c":17:22 -1
(nil))
(insn 14 13 15 (parallel [
(set (zero_extract:SI (subreg:SI (reg:QI 46) 0)
(const_int 1 [0x1])
(const_int 0 [0]))
(subreg:SI (reg:QI 47) 0))
(clobber (scratch:SI))
]) "j.c":17:22 -1
(nil))
Afterwards we generate:
(insn 13 12 14 2 (parallel [
(set (zero_extract:SI (subreg:SI (reg:QI 46) 0)
(const_int 1 [0x1])
(const_int 0 [0]))
(subreg:SI (mem/c:QI (plus:SI (reg/f:SI 37 virtual-stack-vars)
(const_int -5 [0xfffffffffffffffb])) [1 ltrue+0 S1
A8]) 0))
(clobber (scratch:SI))
]) "j.c":17:22 -1
(nil))
Note the (subreg (mem (...)). Probably not desirable in general, but
also note the virtual-stack-vars in the memory address. The code to
instantiate virtual registers doesn't handle (subreg (mem)), so we never
convert that to an FP based address and we eventually fault.
Should be visible with ft32-elf cross compiler. No options needed.
Jeff
