[+Daniel and Jean-Philippe] On Thu, May 23, 2019 at 05:12:00PM +0900, Yoshihiro Shimoda wrote: > The following build warning happens on gcc 8.1.0. > > linux/arch/arm64/include/asm/insn.h: In function 'aarch64_insn_is_ldadd': > linux/arch/arm64/include/asm/insn.h:280:257: warning: bitwise comparison > always evaluates to false [-Wtautological-compare] > __AARCH64_INSN_FUNCS(ldadd, 0x3F20FC00, 0xB8200000) > > Since the second argument is mask value and compare with the third > argument value, the bit 31 is always masked and then this macro is > always false. So, this patch fixes the issue. > > Reported-by: Kuninori Morimoto <[email protected]> > Fixes: 34b8ab091f9ef57a ("bpf, arm64: use more scalable stadd over ldxr / > stxr loop in xadd") > Tested-by: Kuninori Morimoto <[email protected]> > Signed-off-by: Yoshihiro Shimoda <[email protected]> > --- > I'm not sure the second argument "0xBF20FC00" is OK or not (we can set > to 0xFF20FC00 instead). So, I marked RFC on this patch. > > arch/arm64/include/asm/insn.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h > index ec894de..c9e3cdc 100644 > --- a/arch/arm64/include/asm/insn.h > +++ b/arch/arm64/include/asm/insn.h > @@ -277,7 +277,7 @@ __AARCH64_INSN_FUNCS(adrp, 0x9F000000, 0x90000000) > __AARCH64_INSN_FUNCS(prfm, 0x3FC00000, 0x39800000) > __AARCH64_INSN_FUNCS(prfm_lit, 0xFF000000, 0xD8000000) > __AARCH64_INSN_FUNCS(str_reg, 0x3FE0EC00, 0x38206800) > -__AARCH64_INSN_FUNCS(ldadd, 0x3F20FC00, 0xB8200000) > +__AARCH64_INSN_FUNCS(ldadd, 0xBF20FC00, 0xB8200000)
Looking at the ISA encoding, I think that top digit should indeed be 'B', but I haven't checked the rest of the instruction. However, I'm fairly sure we tested this so now I'm a bit worried that I'm missing something :/ Will
