From ade595e377f506471121ce7fea396e97e6728f41 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Wed, 21 Mar 2018 13:51:47 -0400
Subject: [PATCH] bit_util: Do nothing in RotateRight if the rotation amount is
 zero

Without this sanitizing it's possible to perform a shift with a shift
amount that's the same size as the type being shifted. This actually
occurs when decoding ORR variants.

We could get fancier here and make this branchless, but we don't
really use RotateRight in any performance intensive areas.
---
 src/common/bit_util.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/common/bit_util.h b/src/common/bit_util.h
index ae4f83cc..775ccda0 100644
--- a/src/common/bit_util.h
+++ b/src/common/bit_util.h
@@ -130,6 +130,11 @@ inline T Replicate(T value, size_t element_size) {
 template <typename T>
 inline T RotateRight(T value, size_t amount) {
     amount %= BitSize<T>();
+
+    if (amount == 0) {
+        return value;
+    }
+
     auto x = static_cast<std::make_unsigned_t<T>>(value);
     return static_cast<T>((x >> amount) | (x << (BitSize<T>() - amount)));
 }