linux-kernel - [PATCH 2/2] MPILIB: Deobfuscate mpi

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Date:	Sat,  6 Dec 2014 01:00:42 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	David Howells <dhowells@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

The condition preceding 'return 1;' makes my head hurt. At this point,
we know that u and v have the same sign; if they are negative, they
compare opposite to how their absolute values compare (which
mpihelp_cmp found for us), otherwise cmp itself is the
answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
-INT_MIN==INT_MIN won't bite us.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 lib/mpi/mpi-cmp.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
index 3801694240d8..d25e9e96c310 100644
--- a/lib/mpi/mpi-cmp.c
+++ b/lib/mpi/mpi-cmp.c
@@ -61,10 +61,8 @@ int mpi_cmp(MPI u, MPI v)
 	if (!usize)
 		return 0;
 	cmp = mpihelp_cmp(u->d, v->d, usize);
-	if (!cmp)
-		return 0;
-	if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
-		return 1;
-	return -1;
+	if (u->sign)
+		return -cmp;
+	return cmp;
 }
 EXPORT_SYMBOL_GPL(mpi_cmp);
-- 
2.1.3

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