linux-kernel - [PATCH v4 10/21] powerpc/8xx: Duplicate two insns instead of branching

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Message-Id: <20140919083608.6C7BA1AB03B@localhost.localdomain>
Date:	Fri, 19 Sep 2014 10:36:08 +0200 (CEST)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>
CC:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>,
	scottwood@...escale.com
Subject: [PATCH v4 10/21] powerpc/8xx: Duplicate two insns instead of branching

Branching takes two cycles on MPC8xx. Lets duplicate the two instructions
and avoid the branching.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

---
Changes in v2:
- None

Changes in v3:
- None

Changes in v4:
- None

 arch/powerpc/kernel/head_8xx.S |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 5037420..4a49ff3 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -638,9 +638,11 @@ modified_instr:
 
 	/* special handling for r10,r11 since these are modified already */
 153:	mfspr	r11, SPRN_SPRG_SCRATCH1	/* load r11 from SPRN_SPRG_SCRATCH1 */
-	b	155f
+	add	r10, r10, r11	/* add it */
+	mfctr	r11		/* restore r11 */
+	b	151b
 154:	mfspr	r11, SPRN_SPRG_SCRATCH0	/* load r10 from SPRN_SPRG_SCRATCH0 */
-155:	add	r10, r10, r11	/* add it */
+	add	r10, r10, r11	/* add it */
 	mfctr	r11		/* restore r11 */
 	b	151b
 #endif
-- 
1.7.1

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