https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94595
Bug ID: 94595
Summary: gcc.target/arm/thumb2-cond-cmp-*.c fail for cortex-m
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: ---
I've noticed that gcc.target/arm/thumb2-cond-cmp-*.c fail when targeting
cortex-M CPUs.
For thumb2-cond-cmp-1.c, the code generated at svn r196196 for cortex-m3 was:
f:
cmp r1, #45
it ne
cmpne r0, #43
ite ne
movne r0, #0
moveq r0, #1
bx lr
Since r204778, we generate:
f:
cmp r0, #43 @ 8 [c=4 l=2] *arm_cmpsi_insn/0
ittte ne
subne r0, r1, #45 @ 66 [c=8 l=6] *p *arm_subsi3_insn/5
clzne r0, r0 @ 67 [c=8 l=6] *p clzsi2
lsrne r0, r0, #5 @ 68 [c=8 l=6] *p *arm_shiftsi3/1
moveq r0, #1 @ 5 [c=8 l=6] *p *thumb2_movsi_insn/1
bx lr @ 61 [c=8 l=4] *thumb2_return
but using -mcpu=cortex-a9 generates:
f:
cmp r1, #45 @ 26 [c=20 l=6] *cmp_ior/0
it ne
cmpne r0, #43
ite eq
moveq r0, #1 @ 29 [c=8 l=6] *p *thumb2_movsi_insn/1
movne r0, #0 @ 30 [c=8 l=6] *p *thumb2_movsi_insn/1
bx lr @ 33 [c=8 l=4] *thumb2_return
I'm not quite sure about the intent of the test (the comment says "Use
conditional compare"): strictly speaking, the cortex-m3 version does not use
conditional compares, but I'm wondering whether subne can be considered as a
conditional compare? If so, then only the testcases need an update in the
scan-assembler directive.
Or do we want to enforce the use of conditional compare instructions?
FWIW, these tests were introducted in 2011 (r178102) and started failing for
cortex-m in 2013 (r204778), does anyone remember the context?
