https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49263
--- Comment #35 from Alexander Klepikov <klepikov.alex+bugs at gmail dot com>
---
(In reply to Oleg Endo from comment #34)
> Bit-tests of char and unsigned char should be covered by the test-suite and
> should work -- at least originally. However, what might be triggering this
> problem is the '== FLAG' comparison. When I was working on this issue I
> only used '== 0' or '!= 0' comparison. I can imagine that your test code
> triggers some other middle end optimizations and hence we get this.
Yes, I am sure that the problem is the '== FLAG' comparison. Before I reported
that bug, I tried to bypass it and this macro does not produce shift
instructions even on GCC 4.7:
#define BIT_MASK_IS_SET_(VALUE, BITMASK)\
({int _value = VALUE & BITMASK,\
_result;\
if (_value == BITMASK){\
_result = 1;\
}\
else {\
_result = 0;\
}\
_result;})
So this is definitely the comparison.
>
> Can you try to rewrite your test code to something like this?
>
> unsigned int f(char v){
> return (v & FLAG) != 0;
> }
>
> ... and see if it generates the tst instruction as expected?
>
As I understand, you meant the following (I added new functions at the end of
file):
$ cat f.c
#define ADDR 0xFFFF0000
#define P ((unsigned char *)ADDR)
#define FLAG 0x40
#define S 7
unsigned char f_char_var(char v){
return (v & FLAG) == FLAG;
}
unsigned char f_unsigned_char_var(unsigned char v){
return (v & FLAG) == FLAG;
}
unsigned char f_symbol(void){
return (*P & FLAG) == FLAG;
}
unsigned char f_symbol_zero(void){
return (*P & FLAG) == 0;
}
unsigned char f_symbol_non_zero(void){
return (*P & FLAG) != 0;
}
Compiler flags: -c -mrenesas -m2e -mb -O -fno-toplevel-reorder
With patch disabled:
$ cat f_clean.s
.file "f.c"
.text
.text
.align 1
.global _f_char_var
.type _f_char_var, @function
_f_char_var:
sts.l pr,@-r15
mov.l .L3,r1
jsr @r1
exts.b r4,r4
mov r4,r0
and #1,r0
lds.l @r15+,pr
rts
nop
.L4:
.align 2
.L3:
.long ___ashiftrt_r4_6
.size _f_char_var, .-_f_char_var
.align 1
.global _f_unsigned_char_var
.type _f_unsigned_char_var, @function
_f_unsigned_char_var:
sts.l pr,@-r15
mov.l .L7,r1
jsr @r1
exts.b r4,r4
mov r4,r0
and #1,r0
lds.l @r15+,pr
rts
nop
.L8:
.align 2
.L7:
.long ___ashiftrt_r4_6
.size _f_unsigned_char_var, .-_f_unsigned_char_var
.align 1
.global _f_symbol
.type _f_symbol, @function
_f_symbol:
sts.l pr,@-r15
mov.l .L11,r1
mov.b @r1,r4
mov.l .L12,r1
jsr @r1
nop
mov r4,r0
and #1,r0
lds.l @r15+,pr
rts
nop
.L13:
.align 2
.L11:
.long -65536
.L12:
.long ___ashiftrt_r4_6
.size _f_symbol, .-_f_symbol
.align 1
.global _f_symbol_zero
.type _f_symbol_zero, @function
_f_symbol_zero:
mov.l .L15,r1
mov.b @r1,r0
tst #64,r0
rts
movt r0
.L16:
.align 2
.L15:
.long -65536
.size _f_symbol_zero, .-_f_symbol_zero
.align 1
.global _f_symbol_non_zero
.type _f_symbol_non_zero, @function
_f_symbol_non_zero:
sts.l pr,@-r15
mov.l .L19,r1
mov.b @r1,r4
mov.l .L20,r1
jsr @r1
nop
mov r4,r0
and #1,r0
lds.l @r15+,pr
rts
nop
.L21:
.align 2
.L19:
.long -65536
.L20:
.long ___ashiftrt_r4_6
.size _f_symbol_non_zero, .-_f_symbol_non_zero
.ident "GCC: (GNU) 12.3.0"
With patch enabled:
$ cat f.s
.file "f.c"
.text
.text
.align 1
.global _f_char_var
.type _f_char_var, @function
_f_char_var:
mov r4,r0
tst #64,r0
mov #-1,r0
rts
negc r0,r0
.size _f_char_var, .-_f_char_var
.align 1
.global _f_unsigned_char_var
.type _f_unsigned_char_var, @function
_f_unsigned_char_var:
mov r4,r0
tst #64,r0
mov #-1,r0
rts
negc r0,r0
.size _f_unsigned_char_var, .-_f_unsigned_char_var
.align 1
.global _f_symbol
.type _f_symbol, @function
_f_symbol:
mov.l .L4,r1
mov.b @r1,r0
tst #64,r0
mov #-1,r0
rts
negc r0,r0
.L5:
.align 2
.L4:
.long -65536
.size _f_symbol, .-_f_symbol
.align 1
.global _f_symbol_zero
.type _f_symbol_zero, @function
_f_symbol_zero:
mov.l .L7,r1
mov.b @r1,r0
tst #64,r0
rts
movt r0
.L8:
.align 2
.L7:
.long -65536
.size _f_symbol_zero, .-_f_symbol_zero
.align 1
.global _f_symbol_non_zero
.type _f_symbol_non_zero, @function
_f_symbol_non_zero:
mov.l .L10,r1
mov.b @r1,r0
tst #64,r0
mov #-1,r0
rts
negc r0,r0
.L11:
.align 2
.L10:
.long -65536
.size _f_symbol_non_zero, .-_f_symbol_non_zero
.ident "GCC: (GNU) 12.3.0"
> I'm not sure what the purpose of the '-mdisable-dynshift' option would be
> here though. For '-m2e' TARGET_DYNSHIFT is already 'false'. So the option
> seems misnamed.
I choose that name because I wanted to disable dynamic shift instructions for
all CPUs. I did not hope that it will affect SH-2E code in such way.
I can rewrite the patch so that it only affects CPUs that do not support
dynamic shifts and disables library call for dynamic shifts. I'll do it anyway
because I need it badly. How do you think, what name of option would be better:
'-mdisable-dynshift-libcall' or '-mhw-shift'? Or if you want, please suggest
another one. Thank you!
