[Qemu-devel] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Qemu-devel] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Peter Maydell]

The tcg_out* and tcg_patch* functions are utility routines that may or
may not be used by a particular backend; mark them with the 'unused'
attribute to suppress spurious warnings if they aren't used.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Do we want to define a QEMU_UNUSED macro in compiler.h? We don't
seem to have done for the existing uses of this attribute in tree.

 tcg/tcg.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/tcg/tcg.c b/tcg/tcg.c
index 2c5732d..fe55d05 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -125,19 +125,20 @@ static TCGRegSet tcg_target_available_regs[2];
 static TCGRegSet tcg_target_call_clobber_regs;
 
 #if TCG_TARGET_INSN_UNIT_SIZE == 1
-static inline void tcg_out8(TCGContext *s, uint8_t v)
+static __attribute__((unused)) inline void tcg_out8(TCGContext *s, uint8_t v)
 {
     *s->code_ptr++ = v;
 }
 
-static inline void tcg_patch8(tcg_insn_unit *p, uint8_t v)
+static __attribute__((unused)) inline void tcg_patch8(tcg_insn_unit *p,
+                                                      uint8_t v)
 {
     *p = v;
 }
 #endif
 
 #if TCG_TARGET_INSN_UNIT_SIZE <= 2
-static inline void tcg_out16(TCGContext *s, uint16_t v)
+static __attribute__((unused)) inline void tcg_out16(TCGContext *s, uint16_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 2) {
         *s->code_ptr++ = v;
@@ -148,7 +149,8 @@ static inline void tcg_out16(TCGContext *s, uint16_t v)
     }
 }
 
-static inline void tcg_patch16(tcg_insn_unit *p, uint16_t v)
+static __attribute__((unused)) inline void tcg_patch16(tcg_insn_unit *p,
+                                                       uint16_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 2) {
         *p = v;
@@ -159,7 +161,7 @@ static inline void tcg_patch16(tcg_insn_unit *p, uint16_t v)
 #endif
 
 #if TCG_TARGET_INSN_UNIT_SIZE <= 4
-static inline void tcg_out32(TCGContext *s, uint32_t v)
+static __attribute__((unused)) inline void tcg_out32(TCGContext *s, uint32_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 4) {
         *s->code_ptr++ = v;
@@ -170,7 +172,8 @@ static inline void tcg_out32(TCGContext *s, uint32_t v)
     }
 }
 
-static inline void tcg_patch32(tcg_insn_unit *p, uint32_t v)
+static __attribute__((unused)) inline void tcg_patch32(tcg_insn_unit *p,
+                                                       uint32_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 4) {
         *p = v;
@@ -181,7 +184,7 @@ static inline void tcg_patch32(tcg_insn_unit *p, uint32_t v)
 #endif
 
 #if TCG_TARGET_INSN_UNIT_SIZE <= 8
-static inline void tcg_out64(TCGContext *s, uint64_t v)
+static __attribute__((unused)) inline void tcg_out64(TCGContext *s, uint64_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 8) {
         *s->code_ptr++ = v;
@@ -192,7 +195,8 @@ static inline void tcg_out64(TCGContext *s, uint64_t v)
     }
 }
 
-static inline void tcg_patch64(tcg_insn_unit *p, uint64_t v)
+static __attribute__((unused)) inline void tcg_patch64(tcg_insn_unit *p,
+                                                       uint64_t v)
 {
     if (TCG_TARGET_INSN_UNIT_SIZE == 8) {
         *p = v;
-- 
1.8.5.4

Re: [Qemu-devel] [Qemu-trivial] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Michael Tokarev]

07.06.2014 21:08, Peter Maydell wrote:
> The tcg_out* and tcg_patch* functions are utility routines that may or
> may not be used by a particular backend; mark them with the 'unused'
> attribute to suppress spurious warnings if they aren't used.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Do we want to define a QEMU_UNUSED macro in compiler.h? We don't
> seem to have done for the existing uses of this attribute in tree.
> 
>  tcg/tcg.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 2c5732d..fe55d05 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -125,19 +125,20 @@ static TCGRegSet tcg_target_available_regs[2];
>  static TCGRegSet tcg_target_call_clobber_regs;
>  
>  #if TCG_TARGET_INSN_UNIT_SIZE == 1
> -static inline void tcg_out8(TCGContext *s, uint8_t v)

Hm. Those are already #ifdef'ed, is it not enough?  Which architectures
do not use functions which _are_ declared/defined?

But I wonder, why to bother at all?  This "static inline foo() {..}" idiom
is very common in header files, to define a function which may or may not
be used, and no compiler warns about these.

Thanks,

/mjt

Re: [Qemu-devel] [Qemu-trivial] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Peter Maydell]

On 8 June 2014 13:11, Michael Tokarev <mjt@tls.msk.ru> wrote:
> 07.06.2014 21:08, Peter Maydell wrote:
>> The tcg_out* and tcg_patch* functions are utility routines that may or
>> may not be used by a particular backend; mark them with the 'unused'
>> attribute to suppress spurious warnings if they aren't used.
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>> Do we want to define a QEMU_UNUSED macro in compiler.h? We don't
>> seem to have done for the existing uses of this attribute in tree.
>>
>>  tcg/tcg.c | 20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/tcg/tcg.c b/tcg/tcg.c
>> index 2c5732d..fe55d05 100644
>> --- a/tcg/tcg.c
>> +++ b/tcg/tcg.c
>> @@ -125,19 +125,20 @@ static TCGRegSet tcg_target_available_regs[2];
>>  static TCGRegSet tcg_target_call_clobber_regs;
>>
>>  #if TCG_TARGET_INSN_UNIT_SIZE == 1
>> -static inline void tcg_out8(TCGContext *s, uint8_t v)
>
> Hm. Those are already #ifdef'ed, is it not enough?  Which architectures
> do not use functions which _are_ declared/defined?

The tcg x86 backend doesn't use all the tcg_patch* functions.
These ifdefs merely restrict the functions to only be provided
for the backends which conceivably could use them; there is
no requirement that the backend actually does use them.

> But I wonder, why to bother at all?  This "static inline foo() {..}" idiom
> is very common in header files, to define a function which may or may not
> be used, and no compiler warns about these.

clang 3.4 complains, which is why I'm fixing these. (It also found about
half a dozen genuine bugs and quite a bit of legitimately dead code,
which is why I think it's worth dealing with the handful of false positives
like this rather than removing the warning flag.)

thanks
-- PMM

Re: [Qemu-devel] [Qemu-trivial] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Peter Maydell]

On 8 June 2014 13:11, Michael Tokarev <mjt@tls.msk.ru> wrote:
> 07.06.2014 21:08, Peter Maydell wrote:
>> The tcg_out* and tcg_patch* functions are utility routines that may or
>> may not be used by a particular backend; mark them with the 'unused'
>> attribute to suppress spurious warnings if they aren't used.
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>> Do we want to define a QEMU_UNUSED macro in compiler.h? We don't
>> seem to have done for the existing uses of this attribute in tree.
>>
>>  tcg/tcg.c | 20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/tcg/tcg.c b/tcg/tcg.c
>> index 2c5732d..fe55d05 100644
>> --- a/tcg/tcg.c
>> +++ b/tcg/tcg.c
>> @@ -125,19 +125,20 @@ static TCGRegSet tcg_target_available_regs[2];
>>  static TCGRegSet tcg_target_call_clobber_regs;
>>
>>  #if TCG_TARGET_INSN_UNIT_SIZE == 1
>> -static inline void tcg_out8(TCGContext *s, uint8_t v)
>
> Hm. Those are already #ifdef'ed, is it not enough?  Which architectures
> do not use functions which _are_ declared/defined?
>
> But I wonder, why to bother at all?  This "static inline foo() {..}" idiom
> is very common in header files, to define a function which may or may not
> be used, and no compiler warns about these.

The other approach we could take would be to move these
definitions from this .c file into a .h file (tcg-backend-helpers.h ?).
Then clang won't complain (it seems to only warn about unused
static-inline-functions in .c files, not in .h files).

Richard: do you have a preference?

thanks
-- PMM

Re: [Qemu-devel] [Qemu-trivial] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Richard Henderson]

On 06/08/2014 12:04 PM, Peter Maydell wrote:
> The other approach we could take would be to move these
> definitions from this .c file into a .h file (tcg-backend-helpers.h ?).
> Then clang won't complain (it seems to only warn about unused
> static-inline-functions in .c files, not in .h files).
> 
> Richard: do you have a preference?

I don't like the idea of moving these to a public header, and I don't think
it's worthwhile creating a new private header.  I'm ok with the unused attribute.


r~

Re: [Qemu-devel] [Qemu-trivial] [PATCH] tcg: mark tcg_out* and tcg_patch* with attribute 'unused'

[Michael Tokarev]

07.06.2014 21:08, Peter Maydell wrote:
> The tcg_out* and tcg_patch* functions are utility routines that may or
> may not be used by a particular backend; mark them with the 'unused'
> attribute to suppress spurious warnings if they aren't used.

Applied to -trivial, thank you!

/mjt