* [Qemu-devel] [PATCH 2/3] target-mips: Add compiler attribute to some functions which don't return
2012-03-18 22:16 [Qemu-devel] [PATCH 1/3] Add support for target helper functions which don't return Stefan Weil
@ 2012-03-18 22:16 ` Stefan Weil
2012-03-19 10:46 ` Andreas Färber
2012-03-18 22:16 ` [Qemu-devel] [PATCH 3/3] target-sparc: " Stefan Weil
2012-03-19 10:45 ` [Qemu-devel] [PATCH 1/3] Add support for target helper " Andreas Färber
2 siblings, 1 reply; 6+ messages in thread
From: Stefan Weil @ 2012-03-18 22:16 UTC (permalink / raw)
To: qemu-devel, Blue Swirl; +Cc: Stefan Weil, Aurelien Jarno
helper_raise_exception_err does not return, nor do helper_raise_exception
and do_unaligned_access.
Cc: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
target-mips/helper.h | 4 ++--
target-mips/op_helper.c | 3 ++-
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/target-mips/helper.h b/target-mips/helper.h
index 442f684..76fb451 100644
--- a/target-mips/helper.h
+++ b/target-mips/helper.h
@@ -1,7 +1,7 @@
#include "def-helper.h"
-DEF_HELPER_2(raise_exception_err, void, i32, int)
-DEF_HELPER_1(raise_exception, void, i32)
+DEF_HELPER_2(raise_exception_err, noreturn, i32, int)
+DEF_HELPER_1(raise_exception, noreturn, i32)
#ifdef TARGET_MIPS64
DEF_HELPER_3(ldl, tl, tl, tl, int)
diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
index 584f0ab..a825c94 100644
--- a/target-mips/op_helper.c
+++ b/target-mips/op_helper.c
@@ -2274,7 +2274,8 @@ void helper_wait (void)
#if !defined(CONFIG_USER_ONLY)
-static void do_unaligned_access (target_ulong addr, int is_write, int is_user, void *retaddr);
+static void QEMU_NORETURN do_unaligned_access(target_ulong addr, int is_write,
+ int is_user, void *retaddr);
#define MMUSUFFIX _mmu
#define ALIGNED_ONLY
--
1.7.9
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH 2/3] target-mips: Add compiler attribute to some functions which don't return
2012-03-18 22:16 ` [Qemu-devel] [PATCH 2/3] target-mips: Add compiler attribute to some " Stefan Weil
@ 2012-03-19 10:46 ` Andreas Färber
0 siblings, 0 replies; 6+ messages in thread
From: Andreas Färber @ 2012-03-19 10:46 UTC (permalink / raw)
To: Stefan Weil; +Cc: Blue Swirl, qemu-devel, Aurelien Jarno
Am 18.03.2012 23:16, schrieb Stefan Weil:
> helper_raise_exception_err does not return, nor do helper_raise_exception
> and do_unaligned_access.
>
> Cc: Aurelien Jarno <aurelien@aurel32.net>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Andreas
--
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Qemu-devel] [PATCH 3/3] target-sparc: Add compiler attribute to some functions which don't return
2012-03-18 22:16 [Qemu-devel] [PATCH 1/3] Add support for target helper functions which don't return Stefan Weil
2012-03-18 22:16 ` [Qemu-devel] [PATCH 2/3] target-mips: Add compiler attribute to some " Stefan Weil
@ 2012-03-18 22:16 ` Stefan Weil
2012-03-19 10:45 ` [Qemu-devel] [PATCH 1/3] Add support for target helper " Andreas Färber
2 siblings, 0 replies; 6+ messages in thread
From: Stefan Weil @ 2012-03-18 22:16 UTC (permalink / raw)
To: qemu-devel, Blue Swirl; +Cc: Stefan Weil
helper_raise_exception does not return, nor does do_unaligned_access.
Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
target-sparc/cpu.h | 5 +++--
target-sparc/helper.h | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/target-sparc/cpu.h b/target-sparc/cpu.h
index 1025752..885ad45 100644
--- a/target-sparc/cpu.h
+++ b/target-sparc/cpu.h
@@ -699,8 +699,9 @@ uint64_t cpu_tick_get_count(CPUTimer *timer);
void cpu_tick_set_limit(CPUTimer *timer, uint64_t limit);
trap_state* cpu_tsptr(CPUSPARCState* env);
#endif
-void do_unaligned_access(CPUSPARCState *env, target_ulong addr, int is_write,
- int is_user, void *retaddr);
+void QEMU_NORETURN do_unaligned_access(CPUSPARCState *env, target_ulong addr,
+ int is_write, int is_user,
+ void *retaddr);
#define TB_FLAG_FPU_ENABLED (1 << 4)
#define TB_FLAG_AM_ENABLED (1 << 5)
diff --git a/target-sparc/helper.h b/target-sparc/helper.h
index c4d6225..e3c7fdd 100644
--- a/target-sparc/helper.h
+++ b/target-sparc/helper.h
@@ -78,7 +78,7 @@ DEF_HELPER_1(fcmpeq_fcc1, void, env)
DEF_HELPER_1(fcmpeq_fcc2, void, env)
DEF_HELPER_1(fcmpeq_fcc3, void, env)
#endif
-DEF_HELPER_2(raise_exception, void, env, int)
+DEF_HELPER_2(raise_exception, noreturn, env, int)
#define F_HELPER_0_1(name) DEF_HELPER_1(f ## name, void, env)
DEF_HELPER_3(faddd, f64, env, f64, f64)
--
1.7.9
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH 1/3] Add support for target helper functions which don't return
2012-03-18 22:16 [Qemu-devel] [PATCH 1/3] Add support for target helper functions which don't return Stefan Weil
2012-03-18 22:16 ` [Qemu-devel] [PATCH 2/3] target-mips: Add compiler attribute to some " Stefan Weil
2012-03-18 22:16 ` [Qemu-devel] [PATCH 3/3] target-sparc: " Stefan Weil
@ 2012-03-19 10:45 ` Andreas Färber
2012-03-19 11:06 ` Stefan Weil
2 siblings, 1 reply; 6+ messages in thread
From: Andreas Färber @ 2012-03-19 10:45 UTC (permalink / raw)
To: Stefan Weil; +Cc: Blue Swirl, qemu-devel
Am 18.03.2012 23:16, schrieb Stefan Weil:
> Most functions which handle exceptions don't return.
>
> With a compiler attribute (added by QEMU_NORETURN),
> gcc can optimize the code.
Do you have any numbers?
>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
Seems like a sensible optimization,
Reviewed-by: Andreas Färber <afaerber@suse.de>
Andreas
> ---
> def-helper.h | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/def-helper.h b/def-helper.h
> index 0e70c31..b98ff69 100644
> --- a/def-helper.h
> +++ b/def-helper.h
> @@ -39,6 +39,7 @@
> #endif
> #define dh_alias_ptr ptr
> #define dh_alias_void void
> +#define dh_alias_noreturn noreturn
> #define dh_alias_env ptr
> #define dh_alias(t) glue(dh_alias_, t)
>
> @@ -52,36 +53,42 @@
> #define dh_ctype_tl target_ulong
> #define dh_ctype_ptr void *
> #define dh_ctype_void void
> +#define dh_ctype_noreturn void QEMU_NORETURN
> #define dh_ctype_env CPUArchState *
> #define dh_ctype(t) dh_ctype_##t
>
> /* We can't use glue() here because it falls foul of C preprocessor
> recursive expansion rules. */
> #define dh_retvar_decl0_void void
> +#define dh_retvar_decl0_noreturn void
> #define dh_retvar_decl0_i32 TCGv_i32 retval
> #define dh_retvar_decl0_i64 TCGv_i64 retval
> #define dh_retvar_decl0_ptr TCGv_ptr retval
> #define dh_retvar_decl0(t) glue(dh_retvar_decl0_, dh_alias(t))
>
> #define dh_retvar_decl_void
> +#define dh_retvar_decl_noreturn
> #define dh_retvar_decl_i32 TCGv_i32 retval,
> #define dh_retvar_decl_i64 TCGv_i64 retval,
> #define dh_retvar_decl_ptr TCGv_ptr retval,
> #define dh_retvar_decl(t) glue(dh_retvar_decl_, dh_alias(t))
>
> #define dh_retvar_void TCG_CALL_DUMMY_ARG
> +#define dh_retvar_noreturn TCG_CALL_DUMMY_ARG
> #define dh_retvar_i32 GET_TCGV_i32(retval)
> #define dh_retvar_i64 GET_TCGV_i64(retval)
> #define dh_retvar_ptr GET_TCGV_ptr(retval)
> #define dh_retvar(t) glue(dh_retvar_, dh_alias(t))
>
> #define dh_is_64bit_void 0
> +#define dh_is_64bit_noreturn 0
> #define dh_is_64bit_i32 0
> #define dh_is_64bit_i64 1
> #define dh_is_64bit_ptr (TCG_TARGET_REG_BITS == 64)
> #define dh_is_64bit(t) glue(dh_is_64bit_, dh_alias(t))
>
> #define dh_is_signed_void 0
> +#define dh_is_signed_noreturn 0
> #define dh_is_signed_i32 0
> #define dh_is_signed_s32 1
> #define dh_is_signed_i64 0
--
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH 1/3] Add support for target helper functions which don't return
2012-03-19 10:45 ` [Qemu-devel] [PATCH 1/3] Add support for target helper " Andreas Färber
@ 2012-03-19 11:06 ` Stefan Weil
0 siblings, 0 replies; 6+ messages in thread
From: Stefan Weil @ 2012-03-19 11:06 UTC (permalink / raw)
To: Andreas Färber; +Cc: Blue Swirl, qemu-devel
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Am 19.03.2012 11:45, schrieb Andreas Färber:
> Am 18.03.2012 23:16, schrieb Stefan Weil:
>> Most functions which handle exceptions don't return.
>>
>> With a compiler attribute (added by QEMU_NORETURN),
>> gcc can optimize the code.
>
> Do you have any numbers?
Yes, of course: for (;;) { printf("%ld\n", random()); } :-)
To be honest, I don't expect large savings of code (some bytes for the
function return
which is no longer needed), nor will there be a huge gain in execution
speed.
It's more for documentation purposes that this attribute is useful here.
|We might also add a compiler warning for missing attributes some day
(-Wsuggest-attribute=||noreturn|) - it is surprising how many functions
never return!
Regards,
Stefan
>
>>
>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
>
> Seems like a sensible optimization,
>
> Reviewed-by: Andreas Färber <afaerber@suse.de>
>
> Andreas
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^ permalink raw reply [flat|nested] 6+ messages in thread