Re: [Qemu-devel] [PATCH] RISC-V: Fix isa string logic bug, use popcount to count bits

[Michael Clark]

On Sat, Mar 10, 2018 at 9:33 AM, Eric Blake  wrote:

> [resend, this time with proper cc's]
>
> On 03/09/2018 02:20 PM, Michael Clark wrote:
>
>> Cc: Palmer Dabbelt 
>> Cc: Peter Maydell 
>> Signed-off-by: Michael Clark 
>> ---
>>   target/riscv/cpu.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
>> index 4851890..f0d6d1d 100644
>> --- a/target/riscv/cpu.c
>> +++ b/target/riscv/cpu.c
>> @@ -391,7 +391,7 @@ static const TypeInfo riscv_cpu_type_info = {
>>   char *riscv_isa_string(RISCVCPU *cpu)
>>   {
>>   int i;
>> -size_t maxlen = 5 + ctz32(cpu->env.misa);
>> +size_t maxlen = 5 + __builtin_popcountll(cpu->env.misa);
>>   char *isa_string = g_new0(char, maxlen);
>>   snprintf(isa_string, maxlen, "rv%d", TARGET_LONG_BITS);
>>   for (i = 0; i < sizeof(riscv_exts); i++) {
>>
>
> I'd rather you used ctpop64() from host-utils.h, so we have a centralized
> place to change things just once in case we have to tweak the use of
> __builtin_popcount when targetting a different compiler.


Okay. I'll revise the patch...

Re: [Qemu-devel] [PATCH] RISC-V: Fix isa string logic bug, use popcount to count bits

[Eric Blake]

[resend, this time with proper cc's]

On 03/09/2018 02:20 PM, Michael Clark wrote:

Cc: Palmer Dabbelt 
Cc: Peter Maydell 
Signed-off-by: Michael Clark 
---
  target/riscv/cpu.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 4851890..f0d6d1d 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -391,7 +391,7 @@ static const TypeInfo riscv_cpu_type_info = {
  char *riscv_isa_string(RISCVCPU *cpu)
  {
  int i;
-size_t maxlen = 5 + ctz32(cpu->env.misa);
+size_t maxlen = 5 + __builtin_popcountll(cpu->env.misa);
  char *isa_string = g_new0(char, maxlen);
  snprintf(isa_string, maxlen, "rv%d", TARGET_LONG_BITS);
  for (i = 0; i < sizeof(riscv_exts); i++) {


I'd rather you used ctpop64() from host-utils.h, so we have a 
centralized place to change things just once in case we have to tweak 
the use of __builtin_popcount when targetting a different compiler.


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH] RISC-V: Fix isa string logic bug, use popcount to count bits

[Eric Blake]

On 03/09/2018 02:20 PM, Michael Clark wrote:

Cc: Palmer Dabbelt 
Cc: Peter Maydell 
Signed-off-by: Michael Clark 
---
  target/riscv/cpu.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 4851890..f0d6d1d 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -391,7 +391,7 @@ static const TypeInfo riscv_cpu_type_info = {
  char *riscv_isa_string(RISCVCPU *cpu)
  {
  int i;
-size_t maxlen = 5 + ctz32(cpu->env.misa);
+size_t maxlen = 5 + __builtin_popcountll(cpu->env.misa);


I'd rather you used ctpop64() from host-utils.h, so we have a 
centralized place to change things just once in case we have to tweak 
the use of __builtin_popcount when targetting a different compiler.


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

[Qemu-devel] [PATCH] RISC-V: Fix isa string logic bug, use popcount to count bits

[Michael Clark]

Cc: Palmer Dabbelt 
Cc: Peter Maydell 
Signed-off-by: Michael Clark 
---
 target/riscv/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 4851890..f0d6d1d 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -391,7 +391,7 @@ static const TypeInfo riscv_cpu_type_info = {
 char *riscv_isa_string(RISCVCPU *cpu)
 {
 int i;
-size_t maxlen = 5 + ctz32(cpu->env.misa);
+size_t maxlen = 5 + __builtin_popcountll(cpu->env.misa);
 char *isa_string = g_new0(char, maxlen);
 snprintf(isa_string, maxlen, "rv%d", TARGET_LONG_BITS);
 for (i = 0; i < sizeof(riscv_exts); i++) {
-- 
2.7.0