https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64662
Bug ID: 64662
Summary: [SH] QImode/HImode atomics should return sign extended
SImode values
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: olegendo at gcc dot gnu.org
Target: sh*-*-*
Currently, QImode/HImode atomic insns return the values as such, although the
memory loads actually do a sign extension. They should return sign extended
SImode values instead, so that it's easier to eliminate redundant sign/zero
extensions around atomic insns.
Example:
int test4 (volatile char* mem)
{
return __atomic_fetch_add (mem, 1, __ATOMIC_ACQ_REL);
}
compiled with -O2 -m4 -matomic-model=soft-gusa:
mov #1,r3
mova 1f,r0 ! atomic_fetch_addqi_soft_gusa [length = 18]
.align 2
mov r15,r1
mov #(0f-1f),r15
0: mov.b @r4,r2 <<< sign extending load of previous value
mov r2,r7
add r3,r7
mov.b r7,@r4
1: mov r1,r15
rts
exts.b r2,r0 <<< redundant sign extension
