From aa92e33194ef5a8157ab4b36992259ecf77c2ccd 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)));
 }