https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85533
Bug ID: 85533
Summary: Missing optimization for right-shift of unsigned int
(avr-g++)
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: randy.brecker64 at gmail dot com
Target Milestone: ---
If the following snippet is compiled as C++-Code
volatile unsigned char x;
volatile unsigned char y;
int main() {
x >>= 1;
y /= 2;
}
it gives the assembler code:
lds r24,x ; x.0_1, x
ldi r25,0 ; x.0_1
asr r25 ; tmp50
ror r24 ; tmp50
sts x,r24 ; x, tmp50
lds r24,y ; y.1_5, y
lsr r24 ; _6
sts y,r24 ; y, _6
If it is compiled as C-Code it gives a better optimizatoion for the right
shift:
lds r24,x ; x.0_1, x
lsr r24 ; _2
sts x,r24 ; x, _2
lds r24,y ; y.1_3, y
lsr r24 ; _4
sts y,r24 ; y, _4
