Return-Path: From: Siarhei Siamashka To: linux-bluetooth@vger.kernel.org Cc: Siarhei Siamashka Subject: [PATCH] sbc: added "cc" to the clobber list of mmx inline assembly Date: Thu, 11 Nov 2010 11:29:42 +0200 Message-Id: <1289467782-2472-1-git-send-email-siarhei.siamashka@gmail.com> Sender: linux-bluetooth-owner@vger.kernel.org List-ID: From: Siarhei Siamashka In the case of scale factors calculation optimizations, the inline assembly code has instructions which update flags register, but "cc" was not mentioned in the clobber list. When optimizing code, gcc theoretically is allowed to do a comparison before the inline assembly block, and a conditional branch after it which would lead to a problem if the flags register gets clobbered. While this is apparently not happening in practice with the current versions of gcc, the clobber list needs to be corrected. Regarding the other inline assembly blocks. While most likely it is actually unnecessary based on quick review, "cc" is also added there to the clobber list because it should have no impact on performance in practice. It's kind of cargo cult, but relieves us from the need to track the potential updates of flags register in all these places. --- sbc/sbc_primitives_mmx.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/sbc/sbc_primitives_mmx.c b/sbc/sbc_primitives_mmx.c index 45c62ac..7f2fbc3 100644 --- a/sbc/sbc_primitives_mmx.c +++ b/sbc/sbc_primitives_mmx.c @@ -101,7 +101,7 @@ static inline void sbc_analyze_four_mmx(const int16_t *in, int32_t *out, : : "r" (in), "r" (consts), "r" (&round_c), "r" (out), "i" (SBC_PROTO_FIXED4_SCALE) - : "memory"); + : "cc", "memory"); } static inline void sbc_analyze_eight_mmx(const int16_t *in, int32_t *out, @@ -243,7 +243,7 @@ static inline void sbc_analyze_eight_mmx(const int16_t *in, int32_t *out, : : "r" (in), "r" (consts), "r" (&round_c), "r" (out), "i" (SBC_PROTO_FIXED8_SCALE) - : "memory"); + : "cc", "memory"); } static inline void sbc_analyze_4b_4s_mmx(int16_t *x, int32_t *out, @@ -323,7 +323,7 @@ static void sbc_calc_scalefactors_mmx( "r" (&scale_factor[ch][sb]), "r" (&consts), "i" (SCALE_OUT_BITS) - : "memory"); + : "cc", "memory"); } } asm volatile ("emms\n"); -- 1.7.2.2