From 2acbd7ddc0cee21295a1df5416860abb0fdf936f Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 22 Dec 2011 03:15:35 +0000
Subject: [PATCH] Fix APInt::rotl and APInt::rotr so that they work correctly. 
 Found while writing some code that tried to use them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147134 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Support/APInt.cpp | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 143ded920e2..b5411bec9d4 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -1338,14 +1338,10 @@ APInt APInt::rotl(const APInt &rotateAmt) const {
 }
 
 APInt APInt::rotl(unsigned rotateAmt) const {
+  rotateAmt %= BitWidth;
   if (rotateAmt == 0)
     return *this;
-  // Don't get too fancy, just use existing shift/or facilities
-  APInt hi(*this);
-  APInt lo(*this);
-  hi.shl(rotateAmt);
-  lo.lshr(BitWidth - rotateAmt);
-  return hi | lo;
+  return shl(rotateAmt) | lshr(BitWidth - rotateAmt);
 }
 
 APInt APInt::rotr(const APInt &rotateAmt) const {
@@ -1353,14 +1349,10 @@ APInt APInt::rotr(const APInt &rotateAmt) const {
 }
 
 APInt APInt::rotr(unsigned rotateAmt) const {
+  rotateAmt %= BitWidth;
   if (rotateAmt == 0)
     return *this;
-  // Don't get too fancy, just use existing shift/or facilities
-  APInt hi(*this);
-  APInt lo(*this);
-  lo.lshr(rotateAmt);
-  hi.shl(BitWidth - rotateAmt);
-  return hi | lo;
+  return lshr(rotateAmt) | shl(BitWidth - rotateAmt);
 }
 
 // Square Root - this method computes and returns the square root of "this".