https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96769
Bug ID: 96769
Summary: -mpure-code produces suboptimal code for immediate
generation for thumb-1
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: clyon at gcc dot gnu.org
Target Milestone: ---
As discussed in PR94538, -mpure-code produces switch tables for thumb-1.
int f3 (void) { return 0x11000000; }
int f3_2 (void) { return 0x12345678; }
Compiled with -O2 -mpure-code,
-mcpu=cortex-m0:
f3:
movs r0, #17
@ sp needed
lsls r0, r0, #8
lsls r0, r0, #8
lsls r0, r0, #8
bx lr
f3_2:
movs r0, #18
@ sp needed
lsls r0, r0, #8
adds r0, r0, #52
lsls r0, r0, #8
adds r0, r0, #86
lsls r0, r0, #8
adds r0, r0, #120
bx lr
-mcpu=cortex-m23:
f3:
movs r0, #136
@ sp needed
lsls r0, r0, #21
bx lr
f3_2:
movw r0, #22136
@ sp needed
movt r0, 4660
bx lr
Code for cortex-m23 is OK, but the code for cortex-m0 could be improved for
f3(). For f3_2(), code for cortex-m0 looks OK since that CPU does not have
movw/movt instructions.
