http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54685
Bug #: 54685
Summary: [SH] Improve unsigned int comparison with 0x7FFFFFFF
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
AssignedTo: olege...@gcc.gnu.org
ReportedBy: olege...@gcc.gnu.org
Target: sh*-*-*
The following cases:
int test_00 (unsigned int a)
{
return !(a > 0x7FFFFFFF);
}
int test_01 (unsigned int a)
{
return a <= 0x7FFFFFFF;
}
int test_02 (unsigned int a)
{
return a < 0x80000000;
}
compile to (-m4 -O2):
not r4,r0
shll r0
rts
movt r0
which would be better as:
cmp/pz r4 ! T = r4 >= 0 (signed)
rts
movt r0
For some reason, these do not go through the cstoresi4 expander, but the
following does:
int test (unsigned int a)
{
return a > 0;
}
The cstore is expanded by the middle-end into something like
(insn 6 3 7 2 (set (reg:SI 167)
(not:SI (reg/v:SI 164 [ a ]))) sh_tmp.cpp:1984 185 {one_cmplsi2}
(nil))
(insn 7 6 8 2 (parallel [
(set (reg:SI 166 [ D.42391+-3 ])
(lshiftrt:SI (reg:SI 167)
(const_int 31 [0x1f])))
(clobber (reg:SI 147 t))
]) sh_tmp.cpp:1984 167 {lshrsi3_n_clobbers_t}
(nil))
And combine then looks for:
Failed to match this instruction:
(parallel [
(set (reg:SI 166 [ D.42391+-3 ])
(ge:SI (reg:SI 4 r4 [ a ])
(const_int 0 [0])))
(clobber (reg:SI 147 t))
])
