Re: [Qemu-devel] [PATCH] 1/4] target-ppc: Implement bcdcfn. instruction

2016-10-27 Thread joserz 
Hello David,

Thank you very much for your review. As you might have noticed this is my first 
patch so I hope you don't mind about my newbie questions/explanations below.

On Thu, Oct 27, 2016 at 12:05:30PM +1100, David Gibson wrote:
> On Wed, Oct 26, 2016 at 11:18:55AM -0200, Jose Ricardo Ziviani wrote:
> > bcdcfn. converts from National numeric format to BCD. National format
> > uses a byte to represent a digit where the most significant nibble is
> > always 0x3 and the least sign. nibbles is the digit itself.
> > 
> > Signed-off-by: Jose Ricardo Ziviani 
> > ---
> >  target-ppc/helper.h |  1 +
> >  target-ppc/int_helper.c | 54 ++
> >  target-ppc/translate/vmx-impl.inc.c | 75 
> > +
> >  target-ppc/translate/vmx-ops.inc.c  |  4 +-
> >  4 files changed, 132 insertions(+), 2 deletions(-)
> > 
> > diff --git a/target-ppc/helper.h b/target-ppc/helper.h
> > index 04c6421..d30ec60 100644
> > --- a/target-ppc/helper.h
> > +++ b/target-ppc/helper.h
> > @@ -369,6 +369,7 @@ DEF_HELPER_4(vpermxor, void, avr, avr, avr, avr)
> >  
> >  DEF_HELPER_4(bcdadd, i32, avr, avr, avr, i32)
> >  DEF_HELPER_4(bcdsub, i32, avr, avr, avr, i32)
> > +DEF_HELPER_3(bcdcfn, i32, avr, avr, i32)
> >  
> >  DEF_HELPER_2(xsadddp, void, env, i32)
> >  DEF_HELPER_2(xssubdp, void, env, i32)
> > diff --git a/target-ppc/int_helper.c b/target-ppc/int_helper.c
> > index 5aee0a8..494c74e 100644
> > --- a/target-ppc/int_helper.c
> > +++ b/target-ppc/int_helper.c
> > @@ -2417,6 +2417,8 @@ void helper_vsubecuq(ppc_avr_t *r, ppc_avr_t *a, 
> > ppc_avr_t *b, ppc_avr_t *c)
> >  #define BCD_NEG_PREF0xD
> >  #define BCD_NEG_ALT 0xB
> >  #define BCD_PLUS_ALT_2  0xE
> > +#define NATIONAL_PLUS   0x2B
> > +#define NATIONAL_NEG0x2D
> >  
> >  #if defined(HOST_WORDS_BIGENDIAN)
> >  #define BCD_DIG_BYTE(n) (15 - (n/2))
> > @@ -2483,6 +2485,15 @@ static void bcd_put_digit(ppc_avr_t *bcd, uint8_t 
> > digit, int n)
> >  }
> >  }
> >  
> > +static uint8_t get_national_digit(ppc_avr_t *reg, int n)
> > +{
> > +#if defined(HOST_WORDS_BIGENDIAN)
> > +return reg->u16[8 - n] & 0xFF;
> > +#else
> > +return reg->u16[n] & 0xFF;
> > +#endif
> 
> You're discarding the high byte of each digit here, which means you
> won't detect badly encoded values that have correct low bytes.

OK! The high byte is expected to be 0, I'll check if it's != 0 and set a
flag like:

*invalid = (reg->u16[n] >> 8) != 0;

makes sense?

> 
> > +}
> > +
> >  static int bcd_cmp_mag(ppc_avr_t *a, ppc_avr_t *b)
> >  {
> >  int i;
> > @@ -2613,6 +2624,49 @@ uint32_t helper_bcdsub(ppc_avr_t *r,  ppc_avr_t *a, 
> > ppc_avr_t *b, uint32_t ps)
> >  return helper_bcdadd(r, a, , ps);
> >  }
> >  
> > +uint32_t helper_bcdcfn(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
> > +{
> > +int i;
> > +int is_zero = 0;
> > +int cr = 0;
> > +int national = 0;
> > +ppc_avr_t ret = { .u64 = { 0, 0 } };
> > +uint16_t sgnb = get_national_digit(b, 0);
> > +int invalid = (sgnb != NATIONAL_PLUS && sgnb != NATIONAL_NEG);
> > +
> > +for (i = 1; i < 8; i++) {
> > +national = get_national_digit(b, i);
> > +
> > +is_zero += (national == 0x30);
> > +if (unlikely(national < 0x30 || national > 0x39)) {
> > +invalid = 1;
> > +}
> > +
> > +bcd_put_digit(, national & 0xf, i);
> > +}
> > +
> > +if (sgnb == NATIONAL_PLUS ||
> > +(b->u64[0] == 0 && b->u64[1] == 0)) {
> 
> The second part of this test doesn't seem to make much sense.  I think
> you're trying to always put a positive sign on a zero result.  But
> you're testing the national encoded input, not the BCD encoded output,
> and zero will *not* be all zero bits in national encoding.

OK! ISA defines invalid encoding as undefined behavior. I forced a
positive sign to vrt when vrb = 0 (invalid enc.) but it is not necessary.
I'll remove it in v2.

> 
> > +bcd_put_digit(, (ps == 0) ? BCD_PLUS_PREF_1 : BCD_PLUS_PREF_2, 
> > 0);
> > +} else {
> > +bcd_put_digit(, BCD_NEG_PREF, 0);
> > +}
> > +
> > +if (!is_zero) {
> 
> From the logic above, 'is_zero' is currently a count of how many 0
> digits the value has, not whether the value as a whole is zero.  That
> means you will get the wrong result here.
> 

OK! I'll fix that logic.

> > +cr = (sgnb == NATIONAL_PLUS) ? 1 << CRF_GT : 1 << CRF_LT;
> > +} else {
> > +cr = 1 << CRF_EQ;
> > +}
> > +
> > +if (unlikely(invalid)) {
> > +cr = 1 << CRF_SO;
> > +}
> > +
> > +*r = ret;
> > +
> > +return cr;
> > +}
> > +
> >  void helper_vsbox(ppc_avr_t *r, ppc_avr_t *a)
> >  {
> >  int i;
> > diff --git a/target-ppc/translate/vmx-impl.inc.c 
> > b/target-ppc/translate/vmx-impl.inc.c
> > index c8998f3..2abdcac 100644
> > --- a/target-ppc/translate/vmx-impl.inc.c
> > +++ b/target-ppc/translate/vmx-impl.inc.c
> > @@ -871,8 +871,81 @@

Re: [Qemu-devel] [PATCH] 1/4] target-ppc: Implement bcdcfn. instruction

2016-10-26 Thread David Gibson 
On Wed, Oct 26, 2016 at 11:18:55AM -0200, Jose Ricardo Ziviani wrote:
> bcdcfn. converts from National numeric format to BCD. National format
> uses a byte to represent a digit where the most significant nibble is
> always 0x3 and the least sign. nibbles is the digit itself.
> 
> Signed-off-by: Jose Ricardo Ziviani 
> ---
>  target-ppc/helper.h |  1 +
>  target-ppc/int_helper.c | 54 ++
>  target-ppc/translate/vmx-impl.inc.c | 75 
> +
>  target-ppc/translate/vmx-ops.inc.c  |  4 +-
>  4 files changed, 132 insertions(+), 2 deletions(-)
> 
> diff --git a/target-ppc/helper.h b/target-ppc/helper.h
> index 04c6421..d30ec60 100644
> --- a/target-ppc/helper.h
> +++ b/target-ppc/helper.h
> @@ -369,6 +369,7 @@ DEF_HELPER_4(vpermxor, void, avr, avr, avr, avr)
>  
>  DEF_HELPER_4(bcdadd, i32, avr, avr, avr, i32)
>  DEF_HELPER_4(bcdsub, i32, avr, avr, avr, i32)
> +DEF_HELPER_3(bcdcfn, i32, avr, avr, i32)
>  
>  DEF_HELPER_2(xsadddp, void, env, i32)
>  DEF_HELPER_2(xssubdp, void, env, i32)
> diff --git a/target-ppc/int_helper.c b/target-ppc/int_helper.c
> index 5aee0a8..494c74e 100644
> --- a/target-ppc/int_helper.c
> +++ b/target-ppc/int_helper.c
> @@ -2417,6 +2417,8 @@ void helper_vsubecuq(ppc_avr_t *r, ppc_avr_t *a, 
> ppc_avr_t *b, ppc_avr_t *c)
>  #define BCD_NEG_PREF0xD
>  #define BCD_NEG_ALT 0xB
>  #define BCD_PLUS_ALT_2  0xE
> +#define NATIONAL_PLUS   0x2B
> +#define NATIONAL_NEG0x2D
>  
>  #if defined(HOST_WORDS_BIGENDIAN)
>  #define BCD_DIG_BYTE(n) (15 - (n/2))
> @@ -2483,6 +2485,15 @@ static void bcd_put_digit(ppc_avr_t *bcd, uint8_t 
> digit, int n)
>  }
>  }
>  
> +static uint8_t get_national_digit(ppc_avr_t *reg, int n)
> +{
> +#if defined(HOST_WORDS_BIGENDIAN)
> +return reg->u16[8 - n] & 0xFF;
> +#else
> +return reg->u16[n] & 0xFF;
> +#endif

You're discarding the high byte of each digit here, which means you
won't detect badly encoded values that have correct low bytes.

> +}
> +
>  static int bcd_cmp_mag(ppc_avr_t *a, ppc_avr_t *b)
>  {
>  int i;
> @@ -2613,6 +2624,49 @@ uint32_t helper_bcdsub(ppc_avr_t *r,  ppc_avr_t *a, 
> ppc_avr_t *b, uint32_t ps)
>  return helper_bcdadd(r, a, , ps);
>  }
>  
> +uint32_t helper_bcdcfn(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
> +{
> +int i;
> +int is_zero = 0;
> +int cr = 0;
> +int national = 0;
> +ppc_avr_t ret = { .u64 = { 0, 0 } };
> +uint16_t sgnb = get_national_digit(b, 0);
> +int invalid = (sgnb != NATIONAL_PLUS && sgnb != NATIONAL_NEG);
> +
> +for (i = 1; i < 8; i++) {
> +national = get_national_digit(b, i);
> +
> +is_zero += (national == 0x30);
> +if (unlikely(national < 0x30 || national > 0x39)) {
> +invalid = 1;
> +}
> +
> +bcd_put_digit(, national & 0xf, i);
> +}
> +
> +if (sgnb == NATIONAL_PLUS ||
> +(b->u64[0] == 0 && b->u64[1] == 0)) {

The second part of this test doesn't seem to make much sense.  I think
you're trying to always put a positive sign on a zero result.  But
you're testing the national encoded input, not the BCD encoded output,
and zero will *not* be all zero bits in national encoding.

> +bcd_put_digit(, (ps == 0) ? BCD_PLUS_PREF_1 : BCD_PLUS_PREF_2, 
> 0);
> +} else {
> +bcd_put_digit(, BCD_NEG_PREF, 0);
> +}
> +
> +if (!is_zero) {

From the logic above, 'is_zero' is currently a count of how many 0
digits the value has, not whether the value as a whole is zero.  That
means you will get the wrong result here.

> +cr = (sgnb == NATIONAL_PLUS) ? 1 << CRF_GT : 1 << CRF_LT;
> +} else {
> +cr = 1 << CRF_EQ;
> +}
> +
> +if (unlikely(invalid)) {
> +cr = 1 << CRF_SO;
> +}
> +
> +*r = ret;
> +
> +return cr;
> +}
> +
>  void helper_vsbox(ppc_avr_t *r, ppc_avr_t *a)
>  {
>  int i;
> diff --git a/target-ppc/translate/vmx-impl.inc.c 
> b/target-ppc/translate/vmx-impl.inc.c
> index c8998f3..2abdcac 100644
> --- a/target-ppc/translate/vmx-impl.inc.c
> +++ b/target-ppc/translate/vmx-impl.inc.c
> @@ -871,8 +871,81 @@ static void gen_##op(DisasContext *ctx) \
>  tcg_temp_free_i32(ps);  \
>  }
>  
> +#define GEN_BCD2(op)\
> +static void gen_##op(DisasContext *ctx) \
> +{   \
> +TCGv_ptr rd, rb;\
> +TCGv_i32 ps;\
> +\
> +if (unlikely(!ctx->altivec_enabled)) {  \
> +gen_exception(ctx, POWERPC_EXCP_VPU);   \
> +return; \
> +}   \
> +\
> +rb = gen_avr_ptr(rB(ctx->opcode));  \
> +rd =

[Qemu-devel] [PATCH] 1/4] target-ppc: Implement bcdcfn. instruction

2016-10-26 Thread Jose Ricardo Ziviani 
bcdcfn. converts from National numeric format to BCD. National format
uses a byte to represent a digit where the most significant nibble is
always 0x3 and the least sign. nibbles is the digit itself.

Signed-off-by: Jose Ricardo Ziviani 
---
 target-ppc/helper.h |  1 +
 target-ppc/int_helper.c | 54 ++
 target-ppc/translate/vmx-impl.inc.c | 75 +
 target-ppc/translate/vmx-ops.inc.c  |  4 +-
 4 files changed, 132 insertions(+), 2 deletions(-)

diff --git a/target-ppc/helper.h b/target-ppc/helper.h
index 04c6421..d30ec60 100644
--- a/target-ppc/helper.h
+++ b/target-ppc/helper.h
@@ -369,6 +369,7 @@ DEF_HELPER_4(vpermxor, void, avr, avr, avr, avr)
 
 DEF_HELPER_4(bcdadd, i32, avr, avr, avr, i32)
 DEF_HELPER_4(bcdsub, i32, avr, avr, avr, i32)
+DEF_HELPER_3(bcdcfn, i32, avr, avr, i32)
 
 DEF_HELPER_2(xsadddp, void, env, i32)
 DEF_HELPER_2(xssubdp, void, env, i32)
diff --git a/target-ppc/int_helper.c b/target-ppc/int_helper.c
index 5aee0a8..494c74e 100644
--- a/target-ppc/int_helper.c
+++ b/target-ppc/int_helper.c
@@ -2417,6 +2417,8 @@ void helper_vsubecuq(ppc_avr_t *r, ppc_avr_t *a, 
ppc_avr_t *b, ppc_avr_t *c)
 #define BCD_NEG_PREF0xD
 #define BCD_NEG_ALT 0xB
 #define BCD_PLUS_ALT_2  0xE
+#define NATIONAL_PLUS   0x2B
+#define NATIONAL_NEG0x2D
 
 #if defined(HOST_WORDS_BIGENDIAN)
 #define BCD_DIG_BYTE(n) (15 - (n/2))
@@ -2483,6 +2485,15 @@ static void bcd_put_digit(ppc_avr_t *bcd, uint8_t digit, 
int n)
 }
 }
 
+static uint8_t get_national_digit(ppc_avr_t *reg, int n)
+{
+#if defined(HOST_WORDS_BIGENDIAN)
+return reg->u16[8 - n] & 0xFF;
+#else
+return reg->u16[n] & 0xFF;
+#endif
+}
+
 static int bcd_cmp_mag(ppc_avr_t *a, ppc_avr_t *b)
 {
 int i;
@@ -2613,6 +2624,49 @@ uint32_t helper_bcdsub(ppc_avr_t *r,  ppc_avr_t *a, 
ppc_avr_t *b, uint32_t ps)
 return helper_bcdadd(r, a, , ps);
 }
 
+uint32_t helper_bcdcfn(ppc_avr_t *r, ppc_avr_t *b, uint32_t ps)
+{
+int i;
+int is_zero = 0;
+int cr = 0;
+int national = 0;
+ppc_avr_t ret = { .u64 = { 0, 0 } };
+uint16_t sgnb = get_national_digit(b, 0);
+int invalid = (sgnb != NATIONAL_PLUS && sgnb != NATIONAL_NEG);
+
+for (i = 1; i < 8; i++) {
+national = get_national_digit(b, i);
+
+is_zero += (national == 0x30);
+if (unlikely(national < 0x30 || national > 0x39)) {
+invalid = 1;
+}
+
+bcd_put_digit(, national & 0xf, i);
+}
+
+if (sgnb == NATIONAL_PLUS ||
+(b->u64[0] == 0 && b->u64[1] == 0)) {
+bcd_put_digit(, (ps == 0) ? BCD_PLUS_PREF_1 : BCD_PLUS_PREF_2, 0);
+} else {
+bcd_put_digit(, BCD_NEG_PREF, 0);
+}
+
+if (!is_zero) {
+cr = (sgnb == NATIONAL_PLUS) ? 1 << CRF_GT : 1 << CRF_LT;
+} else {
+cr = 1 << CRF_EQ;
+}
+
+if (unlikely(invalid)) {
+cr = 1 << CRF_SO;
+}
+
+*r = ret;
+
+return cr;
+}
+
 void helper_vsbox(ppc_avr_t *r, ppc_avr_t *a)
 {
 int i;
diff --git a/target-ppc/translate/vmx-impl.inc.c 
b/target-ppc/translate/vmx-impl.inc.c
index c8998f3..2abdcac 100644
--- a/target-ppc/translate/vmx-impl.inc.c
+++ b/target-ppc/translate/vmx-impl.inc.c
@@ -871,8 +871,81 @@ static void gen_##op(DisasContext *ctx) \
 tcg_temp_free_i32(ps);  \
 }
 
+#define GEN_BCD2(op)\
+static void gen_##op(DisasContext *ctx) \
+{   \
+TCGv_ptr rd, rb;\
+TCGv_i32 ps;\
+\
+if (unlikely(!ctx->altivec_enabled)) {  \
+gen_exception(ctx, POWERPC_EXCP_VPU);   \
+return; \
+}   \
+\
+rb = gen_avr_ptr(rB(ctx->opcode));  \
+rd = gen_avr_ptr(rD(ctx->opcode));  \
+\
+ps = tcg_const_i32((ctx->opcode & 0x200) != 0); \
+\
+gen_helper_##op(cpu_crf[6], rd, rb, ps);\
+\
+tcg_temp_free_ptr(rb);  \
+tcg_temp_free_ptr(rd);  \
+tcg_temp_free_i32(ps);  \
+}
+
 GEN_BCD(bcdadd)
 GEN_BCD(bcdsub)
+GEN_BCD2(bcdcfn)
+
+static void gen_xpnd04_1(DisasContext *ctx)
+{
+switch (opc4(ctx->opcode)) {
+case 0:
+break; /* bcdctsq. */
+case 2:
+break; /* bcdcfsq. */
+case 4:
+break; /* bcdctz. */
+case 5:
+break; /* bcdctn. */
+case 6:
+break; /* bcdcfz. */
+case 7:
+gen_bcdcfn(ctx);
+break;
+case 31:
+break;