https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101981
--- Comment #7 from Thibaut M. <dumoulin.thibaut at gmail dot com> ---
There are other regressions (in term of code size) but not sure if this is the
same.
For example, this code:
```C
#include <stdio.h>
void big_switch(int a) {
switch (a) {
default:
printf("default a(%d)\n", a);
case 0x1:
case 0x2:
// case 0x3:
// case 0x4:
case 0x5:
case 0x6:
// case 0x7:
// case 0x8:
// case 0x9:
case 0xA:
case 0xD:
case 0xE:
case 0xF:
// case 0x10:
case 0x11:
case 0x12:
// case 0x13:
// case 0x14:
case 0x15:
case 0x17:
case 0x18:
case 0x19:
case 0x1A:
// case 0x1B:
case 0x1C:
case 0x1D: {
printf("a(%d)\n", a);
} break;
}
}
int main(void) {
big_switch(2);
return 0;
}
```
with compile parameters `arm-none-eabi-gcc -Os -mcpu=cortex-m4 ./switch.c`
the asm is lighter with GCC7.3.1 than with GCC10.3.1.
While GCC7.3.1 (20 lines)
```asm
00008134 <big_switch>:
cmp r0, #29
push {r4, lr}
mov r4, r0
bhi.n 8146 <big_switch+0x12>
movs r2, #1
ldr r3, [pc, #28] ; (815c <big_switch+0x28>)
lsls r2, r0
ands r3, r2
cbnz r3, 814e <big_switch+0x1a>
mov r1, r4
ldr r0, [pc, #20] ; (8160 <big_switch+0x2c>)
bl 8264 <printf>
mov r1, r4
ldr r0, [pc, #16] ; (8164 <big_switch+0x30>)
ldmia.w sp!, {r4, lr}
b.w 8264 <printf>
nop
.word 0x37a6e466
.word 0x0000f5f8
.word 0x0000f600
```
GCC10.3.1 (24 lines)
```asm
0000813c <big_switch>:
subs r3, r0, #1
push {r4, lr}
mov r4, r0
cmp r3, #28
bhi.n 8168 <big_switch+0x2c>
tbb [pc, r3]
.short 0x1313
.word 0x13130f0f
.word 0x130f0f0f
.word 0x13130f0f
.word 0x13130f13
.word 0x0f130f0f
.word 0x13131313
.short 0x130f
.byte 0x13
.byte 0x00
mov r1, r0
ldr r0, [pc, #16] ; (817c <big_switch+0x40>)
bl 828c <printf>
mov r1, r4
ldr r0, [pc, #8] ; (817c <big_switch+0x40>)
ldmia.w sp!, {r4, lr}
b.w 828c <printf>
.word 0x0001011c
```
Not a big difference in term of instructions is this case but as much as the
switch increases, the difference becomes huge (in my case it switched from 75
to 94 lines)
Code size increases of about 10%.
@Martin, do you know if this is linked?
