| Message ID | 20170724010109.21263-2-matthew.brown.dev@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
Hi Matt, On Mon, Jul 24, 2017 at 11:01:06AM +1000, Matt Brown wrote: > + for (i = 0; i < (64 / size); i++) { If you do for (i = 0; i < 64; i += size) things are slightly nicer. > + if ((i * size) < 32) > + low |= n << (i * size); > + else > + high |= n << ((i * size) - 32); > + } > + regs->gpr[ra] = (high << 32) | low; Why have separate high and low vars? And there are much better ways to calculate popcount, of course. Segher
On Mon, Jul 24, 2017 at 11:01 AM, Matt Brown <matthew.brown.dev@gmail.com> wrote: > This adds emulations for the popcntb, popcntw, and popcntd instructions. > Tested for correctness against the popcnt{b,w,d} instructions on ppc64le. > > Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com> > --- > v2: > - fixed opcodes > - fixed typecasting > - fixed bitshifting error for both 32 and 64bit arch > --- > arch/powerpc/lib/sstep.c | 43 ++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 42 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c > index 87d277f..e6a16a3 100644 > --- a/arch/powerpc/lib/sstep.c > +++ b/arch/powerpc/lib/sstep.c > @@ -612,6 +612,35 @@ static nokprobe_inline void do_cmpb(struct pt_regs *regs, unsigned long v1, > regs->gpr[rd] = out_val; > } > > +/* > + * The size parameter is used to adjust the equivalent popcnt instruction. > + * popcntb = 8, popcntw = 32, popcntd = 64 > + */ > +static nokprobe_inline void do_popcnt(struct pt_regs *regs, unsigned long v1, > + int size, int ra) > +{ > + unsigned long long high, low, mask; > + unsigned int n; > + int i, j; > + > + high = 0; > + low = 0; > + > + for (i = 0; i < (64 / size); i++) { > + n = 0; > + for (j = 0; j < size; j++) { > + mask = 1UL << (j + (i * size)); > + if (v1 & mask) > + n++; > + } > + if ((i * size) < 32) > + low |= n << (i * size); > + else > + high |= n << ((i * size) - 32); > + } > + regs->gpr[ra] = (high << 32) | low; > +} There's a way to do it in very efficient way via the Giles-Miller method of side-ways addition Please see http://opensourceforu.com/2012/06/power-programming-bitwise-tips-tricks/ and lib/hweight.c, you can reuse the code from lib/hweight.c Balbir Singh
On Mon, Jul 24, 2017 at 8:28 PM, Balbir Singh <bsingharora@gmail.com> wrote: > On Mon, Jul 24, 2017 at 11:01 AM, Matt Brown > <matthew.brown.dev@gmail.com> wrote: >> This adds emulations for the popcntb, popcntw, and popcntd instructions. >> Tested for correctness against the popcnt{b,w,d} instructions on ppc64le. >> >> Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com> >> --- >> v2: >> - fixed opcodes >> - fixed typecasting >> - fixed bitshifting error for both 32 and 64bit arch >> --- >> arch/powerpc/lib/sstep.c | 43 ++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 42 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c >> index 87d277f..e6a16a3 100644 >> --- a/arch/powerpc/lib/sstep.c >> +++ b/arch/powerpc/lib/sstep.c >> @@ -612,6 +612,35 @@ static nokprobe_inline void do_cmpb(struct pt_regs *regs, unsigned long v1, >> regs->gpr[rd] = out_val; >> } >> >> +/* >> + * The size parameter is used to adjust the equivalent popcnt instruction. >> + * popcntb = 8, popcntw = 32, popcntd = 64 >> + */ >> +static nokprobe_inline void do_popcnt(struct pt_regs *regs, unsigned long v1, >> + int size, int ra) >> +{ >> + unsigned long long high, low, mask; >> + unsigned int n; >> + int i, j; >> + >> + high = 0; >> + low = 0; >> + >> + for (i = 0; i < (64 / size); i++) { >> + n = 0; >> + for (j = 0; j < size; j++) { >> + mask = 1UL << (j + (i * size)); >> + if (v1 & mask) >> + n++; >> + } >> + if ((i * size) < 32) >> + low |= n << (i * size); >> + else >> + high |= n << ((i * size) - 32); >> + } >> + regs->gpr[ra] = (high << 32) | low; >> +} > > There's a way to do it in very efficient way via the Giles-Miller > method of side-ways addition > > Please see > > http://opensourceforu.com/2012/06/power-programming-bitwise-tips-tricks/ > and lib/hweight.c, you can reuse the code from lib/hweight.c Oh that's a really cool technique. We could use that for the parity instructions too. > > Balbir Singh
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index 87d277f..e6a16a3 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -612,6 +612,35 @@ static nokprobe_inline void do_cmpb(struct pt_regs *regs, unsigned long v1, regs->gpr[rd] = out_val; } +/* + * The size parameter is used to adjust the equivalent popcnt instruction. + * popcntb = 8, popcntw = 32, popcntd = 64 + */ +static nokprobe_inline void do_popcnt(struct pt_regs *regs, unsigned long v1, + int size, int ra) +{ + unsigned long long high, low, mask; + unsigned int n; + int i, j; + + high = 0; + low = 0; + + for (i = 0; i < (64 / size); i++) { + n = 0; + for (j = 0; j < size; j++) { + mask = 1UL << (j + (i * size)); + if (v1 & mask) + n++; + } + if ((i * size) < 32) + low |= n << (i * size); + else + high |= n << ((i * size) - 32); + } + regs->gpr[ra] = (high << 32) | low; +} + static nokprobe_inline int trap_compare(long v1, long v2) { int ret = 0; @@ -1194,6 +1223,10 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs, regs->gpr[ra] = regs->gpr[rd] & ~regs->gpr[rb]; goto logical_done; + case 122: /* popcntb */ + do_popcnt(regs, regs->gpr[rd], 8, ra); + goto logical_done; + case 124: /* nor */ regs->gpr[ra] = ~(regs->gpr[rd] | regs->gpr[rb]); goto logical_done; @@ -1206,6 +1239,10 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs, regs->gpr[ra] = regs->gpr[rd] ^ regs->gpr[rb]; goto logical_done; + case 378: /* popcntw */ + do_popcnt(regs, regs->gpr[rd], 32, ra); + goto logical_done; + case 412: /* orc */ regs->gpr[ra] = regs->gpr[rd] | ~regs->gpr[rb]; goto logical_done; @@ -1217,7 +1254,11 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs, case 476: /* nand */ regs->gpr[ra] = ~(regs->gpr[rd] & regs->gpr[rb]); goto logical_done; - +#ifdef __powerpc64__ + case 506: /* popcntd */ + do_popcnt(regs, regs->gpr[rd], 64, ra); + goto logical_done; +#endif case 922: /* extsh */ regs->gpr[ra] = (signed short) regs->gpr[rd]; goto logical_done;
This adds emulations for the popcntb, popcntw, and popcntd instructions. Tested for correctness against the popcnt{b,w,d} instructions on ppc64le. Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com> --- v2: - fixed opcodes - fixed typecasting - fixed bitshifting error for both 32 and 64bit arch --- arch/powerpc/lib/sstep.c | 43 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-)