* [Qemu-devel] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output
@ 2013-04-03 20:56 Richard Henderson
2013-04-03 21:15 ` Aurelien Jarno
2013-04-04 12:43 ` [Qemu-devel] [Qemu-ppc] " Alexander Graf
0 siblings, 2 replies; 3+ messages in thread
From: Richard Henderson @ 2013-04-03 20:56 UTC (permalink / raw)
To: qemu-devel; +Cc: qemu-ppc, Aurelien Jarno
Broken in b5a73f8d8a57e940f9bbeb399a9e47897522ee9a, the carry itself was
fixed in 79482e5ab38a05ca8869040b0d8b8f451f16ff62. But we still need to
produce the full 64-bit addition.
Simplify the conditions at the top of the functions for when we need a
new temporary. Only plain addition is important enough to warrent avoiding
the temporary, and the extra tcg move op that would come with it.
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
Version 2 fixes the temporary creation problem spotted by Aurelien.
---
target-ppc/translate.c | 35 ++++++++++++++++++++++-------------
1 file changed, 22 insertions(+), 13 deletions(-)
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 5e741d1..fa1778a 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -768,22 +768,25 @@ static inline void gen_op_arith_add(DisasContext *ctx, TCGv ret, TCGv arg1,
{
TCGv t0 = ret;
- if (((compute_ca && add_ca) || compute_ov)
- && (TCGV_EQUAL(ret, arg1) || TCGV_EQUAL(ret, arg2))) {
+ if (compute_ca || compute_ov) {
t0 = tcg_temp_new();
}
if (compute_ca) {
if (NARROW_MODE(ctx)) {
+ /* Caution: a non-obvious corner case of the spec is that we
+ must produce the *entire* 64-bit addition, but produce the
+ carry into bit 32. */
TCGv t1 = tcg_temp_new();
- tcg_gen_ext32u_tl(t1, arg2);
- tcg_gen_ext32u_tl(t0, arg1);
- tcg_gen_add_tl(t0, t0, t1);
- tcg_temp_free(t1);
+ tcg_gen_xor_tl(t1, arg1, arg2); /* add without carry */
+ tcg_gen_add_tl(t0, arg1, arg2);
if (add_ca) {
tcg_gen_add_tl(t0, t0, cpu_ca);
}
- tcg_gen_shri_tl(cpu_ca, t0, 32);
+ tcg_gen_xor_tl(cpu_ca, t0, t1); /* bits changed w/ carry */
+ tcg_temp_free(t1);
+ tcg_gen_shri_tl(cpu_ca, cpu_ca, 32); /* extract bit 32 */
+ tcg_gen_andi_tl(cpu_ca, cpu_ca, 1);
} else {
TCGv zero = tcg_const_tl(0);
if (add_ca) {
@@ -1122,24 +1125,30 @@ static inline void gen_op_arith_subf(DisasContext *ctx, TCGv ret, TCGv arg1,
{
TCGv t0 = ret;
- if (compute_ov && (TCGV_EQUAL(ret, arg1) || TCGV_EQUAL(ret, arg2))) {
+ if (compute_ca || compute_ov) {
t0 = tcg_temp_new();
}
if (compute_ca) {
/* dest = ~arg1 + arg2 [+ ca]. */
if (NARROW_MODE(ctx)) {
+ /* Caution: a non-obvious corner case of the spec is that we
+ must produce the *entire* 64-bit addition, but produce the
+ carry into bit 32. */
TCGv inv1 = tcg_temp_new();
+ TCGv t1 = tcg_temp_new();
tcg_gen_not_tl(inv1, arg1);
- tcg_gen_ext32u_tl(t0, arg2);
- tcg_gen_ext32u_tl(inv1, inv1);
if (add_ca) {
- tcg_gen_add_tl(t0, t0, cpu_ca);
+ tcg_gen_add_tl(t0, arg2, cpu_ca);
} else {
- tcg_gen_addi_tl(t0, t0, 1);
+ tcg_gen_addi_tl(t0, arg2, 1);
}
+ tcg_gen_xor_tl(t1, arg2, inv1); /* add without carry */
tcg_gen_add_tl(t0, t0, inv1);
- tcg_gen_shri_tl(cpu_ca, t0, 32);
+ tcg_gen_xor_tl(cpu_ca, t0, t1); /* bits changes w/ carry */
+ tcg_temp_free(t1);
+ tcg_gen_shri_tl(cpu_ca, cpu_ca, 32); /* extract bit 32 */
+ tcg_gen_andi_tl(cpu_ca, cpu_ca, 1);
} else if (add_ca) {
TCGv zero, inv1 = tcg_temp_new();
tcg_gen_not_tl(inv1, arg1);
--
1.8.1.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output
2013-04-03 20:56 [Qemu-devel] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output Richard Henderson
@ 2013-04-03 21:15 ` Aurelien Jarno
2013-04-04 12:43 ` [Qemu-devel] [Qemu-ppc] " Alexander Graf
1 sibling, 0 replies; 3+ messages in thread
From: Aurelien Jarno @ 2013-04-03 21:15 UTC (permalink / raw)
To: Richard Henderson; +Cc: qemu-ppc, qemu-devel
On Wed, Apr 03, 2013 at 03:56:45PM -0500, Richard Henderson wrote:
> Broken in b5a73f8d8a57e940f9bbeb399a9e47897522ee9a, the carry itself was
> fixed in 79482e5ab38a05ca8869040b0d8b8f451f16ff62. But we still need to
> produce the full 64-bit addition.
>
> Simplify the conditions at the top of the functions for when we need a
> new temporary. Only plain addition is important enough to warrent avoiding
> the temporary, and the extra tcg move op that would come with it.
>
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
> Version 2 fixes the temporary creation problem spotted by Aurelien.
> ---
>
> target-ppc/translate.c | 35 ++++++++++++++++++++++-------------
> 1 file changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 5e741d1..fa1778a 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -768,22 +768,25 @@ static inline void gen_op_arith_add(DisasContext *ctx, TCGv ret, TCGv arg1,
> {
> TCGv t0 = ret;
>
> - if (((compute_ca && add_ca) || compute_ov)
> - && (TCGV_EQUAL(ret, arg1) || TCGV_EQUAL(ret, arg2))) {
> + if (compute_ca || compute_ov) {
> t0 = tcg_temp_new();
> }
>
> if (compute_ca) {
> if (NARROW_MODE(ctx)) {
> + /* Caution: a non-obvious corner case of the spec is that we
> + must produce the *entire* 64-bit addition, but produce the
> + carry into bit 32. */
> TCGv t1 = tcg_temp_new();
> - tcg_gen_ext32u_tl(t1, arg2);
> - tcg_gen_ext32u_tl(t0, arg1);
> - tcg_gen_add_tl(t0, t0, t1);
> - tcg_temp_free(t1);
> + tcg_gen_xor_tl(t1, arg1, arg2); /* add without carry */
> + tcg_gen_add_tl(t0, arg1, arg2);
> if (add_ca) {
> tcg_gen_add_tl(t0, t0, cpu_ca);
> }
> - tcg_gen_shri_tl(cpu_ca, t0, 32);
> + tcg_gen_xor_tl(cpu_ca, t0, t1); /* bits changed w/ carry */
> + tcg_temp_free(t1);
> + tcg_gen_shri_tl(cpu_ca, cpu_ca, 32); /* extract bit 32 */
> + tcg_gen_andi_tl(cpu_ca, cpu_ca, 1);
> } else {
> TCGv zero = tcg_const_tl(0);
> if (add_ca) {
> @@ -1122,24 +1125,30 @@ static inline void gen_op_arith_subf(DisasContext *ctx, TCGv ret, TCGv arg1,
> {
> TCGv t0 = ret;
>
> - if (compute_ov && (TCGV_EQUAL(ret, arg1) || TCGV_EQUAL(ret, arg2))) {
> + if (compute_ca || compute_ov) {
> t0 = tcg_temp_new();
> }
>
> if (compute_ca) {
> /* dest = ~arg1 + arg2 [+ ca]. */
> if (NARROW_MODE(ctx)) {
> + /* Caution: a non-obvious corner case of the spec is that we
> + must produce the *entire* 64-bit addition, but produce the
> + carry into bit 32. */
> TCGv inv1 = tcg_temp_new();
> + TCGv t1 = tcg_temp_new();
> tcg_gen_not_tl(inv1, arg1);
> - tcg_gen_ext32u_tl(t0, arg2);
> - tcg_gen_ext32u_tl(inv1, inv1);
> if (add_ca) {
> - tcg_gen_add_tl(t0, t0, cpu_ca);
> + tcg_gen_add_tl(t0, arg2, cpu_ca);
> } else {
> - tcg_gen_addi_tl(t0, t0, 1);
> + tcg_gen_addi_tl(t0, arg2, 1);
> }
> + tcg_gen_xor_tl(t1, arg2, inv1); /* add without carry */
> tcg_gen_add_tl(t0, t0, inv1);
> - tcg_gen_shri_tl(cpu_ca, t0, 32);
> + tcg_gen_xor_tl(cpu_ca, t0, t1); /* bits changes w/ carry */
> + tcg_temp_free(t1);
> + tcg_gen_shri_tl(cpu_ca, cpu_ca, 32); /* extract bit 32 */
> + tcg_gen_andi_tl(cpu_ca, cpu_ca, 1);
> } else if (add_ca) {
> TCGv zero, inv1 = tcg_temp_new();
> tcg_gen_not_tl(inv1, arg1);
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output
2013-04-03 20:56 [Qemu-devel] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output Richard Henderson
2013-04-03 21:15 ` Aurelien Jarno
@ 2013-04-04 12:43 ` Alexander Graf
1 sibling, 0 replies; 3+ messages in thread
From: Alexander Graf @ 2013-04-04 12:43 UTC (permalink / raw)
To: Richard Henderson; +Cc: qemu-ppc, qemu-devel
On 03.04.2013, at 22:56, Richard Henderson wrote:
> Broken in b5a73f8d8a57e940f9bbeb399a9e47897522ee9a, the carry itself was
> fixed in 79482e5ab38a05ca8869040b0d8b8f451f16ff62. But we still need to
> produce the full 64-bit addition.
>
> Simplify the conditions at the top of the functions for when we need a
> new temporary. Only plain addition is important enough to warrent avoiding
> the temporary, and the extra tcg move op that would come with it.
>
> Signed-off-by: Richard Henderson <rth@twiddle.net>
Thanks, applied to ppc-next.
Alex
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-04-03 20:56 [Qemu-devel] [PATCH v2] target-ppc: Fix narrow-mode add/sub carry output Richard Henderson
2013-04-03 21:15 ` Aurelien Jarno
2013-04-04 12:43 ` [Qemu-devel] [Qemu-ppc] " Alexander Graf
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