linux-kernel - [PATCH v2 1/2] powerpc: avoid an unnecessary test and branch in longjmp()

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Date:   Tue, 17 Apr 2018 19:08:16 +0200 (CEST)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 1/2] powerpc: avoid an unnecessary test and branch in
 longjmp()

Doing the test at exit of the function avoids an unnecessary
test and branch inside longjmp()

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 v2: Swapped both patches in the serie to reduce number of impacted lines

 arch/powerpc/kernel/misc.S | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index e1f3a5d054c4..746ee0320ad4 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -74,10 +74,7 @@ _GLOBAL(setjmp)
 	blr
 
 _GLOBAL(longjmp)
-	PPC_LCMPI r4,0
-	bne	1f
-	li	r4,1
-1:	PPC_LL	r13,4*SZL(r3)
+	PPC_LL	r13,4*SZL(r3)
 	PPC_LL	r14,5*SZL(r3)
 	PPC_LL	r15,6*SZL(r3)
 	PPC_LL	r16,7*SZL(r3)
@@ -102,7 +99,9 @@ _GLOBAL(longjmp)
 	PPC_LL	r1,SZL(r3)
 	PPC_LL	r2,2*SZL(r3)
 	mtlr	r0
-	mr	r3,r4
+	mr.	r3, r4
+	bnelr
+	li	r3, 1
 	blr
 
 _GLOBAL(current_stack_pointer)
-- 
2.13.3